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5926 lines
157 KiB
5926 lines
157 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Generic ring buffer |
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* |
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* Copyright (C) 2008 Steven Rostedt <[email protected]> |
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*/ |
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#include <linux/trace_recursion.h> |
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#include <linux/trace_events.h> |
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#include <linux/ring_buffer.h> |
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#include <linux/trace_clock.h> |
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#include <linux/sched/clock.h> |
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#include <linux/trace_seq.h> |
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#include <linux/spinlock.h> |
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#include <linux/irq_work.h> |
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#include <linux/security.h> |
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#include <linux/uaccess.h> |
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#include <linux/hardirq.h> |
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#include <linux/kthread.h> /* for self test */ |
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#include <linux/module.h> |
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#include <linux/percpu.h> |
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#include <linux/mutex.h> |
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#include <linux/delay.h> |
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#include <linux/slab.h> |
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#include <linux/init.h> |
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#include <linux/hash.h> |
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#include <linux/list.h> |
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#include <linux/cpu.h> |
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#include <linux/oom.h> |
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|
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#include <asm/local.h> |
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|
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static void update_pages_handler(struct work_struct *work); |
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|
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/* |
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* The ring buffer header is special. We must manually up keep it. |
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*/ |
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int ring_buffer_print_entry_header(struct trace_seq *s) |
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{ |
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trace_seq_puts(s, "# compressed entry header\n"); |
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trace_seq_puts(s, "\ttype_len : 5 bits\n"); |
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trace_seq_puts(s, "\ttime_delta : 27 bits\n"); |
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trace_seq_puts(s, "\tarray : 32 bits\n"); |
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trace_seq_putc(s, '\n'); |
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trace_seq_printf(s, "\tpadding : type == %d\n", |
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RINGBUF_TYPE_PADDING); |
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trace_seq_printf(s, "\ttime_extend : type == %d\n", |
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RINGBUF_TYPE_TIME_EXTEND); |
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trace_seq_printf(s, "\ttime_stamp : type == %d\n", |
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RINGBUF_TYPE_TIME_STAMP); |
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trace_seq_printf(s, "\tdata max type_len == %d\n", |
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RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
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return !trace_seq_has_overflowed(s); |
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} |
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|
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/* |
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* The ring buffer is made up of a list of pages. A separate list of pages is |
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* allocated for each CPU. A writer may only write to a buffer that is |
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* associated with the CPU it is currently executing on. A reader may read |
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* from any per cpu buffer. |
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* |
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* The reader is special. For each per cpu buffer, the reader has its own |
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* reader page. When a reader has read the entire reader page, this reader |
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* page is swapped with another page in the ring buffer. |
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* |
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* Now, as long as the writer is off the reader page, the reader can do what |
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* ever it wants with that page. The writer will never write to that page |
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* again (as long as it is out of the ring buffer). |
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* |
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* Here's some silly ASCII art. |
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* |
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* +------+ |
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* |reader| RING BUFFER |
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* |page | |
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* +------+ +---+ +---+ +---+ |
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* | |-->| |-->| | |
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* +---+ +---+ +---+ |
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* ^ | |
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* | | |
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* +---------------+ |
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* |
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* |
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* +------+ |
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* |reader| RING BUFFER |
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* |page |------------------v |
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* +------+ +---+ +---+ +---+ |
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* | |-->| |-->| | |
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* +---+ +---+ +---+ |
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* ^ | |
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* | | |
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* +---------------+ |
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* |
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* |
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* +------+ |
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* |reader| RING BUFFER |
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* |page |------------------v |
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* +------+ +---+ +---+ +---+ |
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* ^ | |-->| |-->| | |
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* | +---+ +---+ +---+ |
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* | | |
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* | | |
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* +------------------------------+ |
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* |
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* |
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* +------+ |
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* |buffer| RING BUFFER |
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* |page |------------------v |
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* +------+ +---+ +---+ +---+ |
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* ^ | | | |-->| | |
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* | New +---+ +---+ +---+ |
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* | Reader------^ | |
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* | page | |
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* +------------------------------+ |
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* |
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* |
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* After we make this swap, the reader can hand this page off to the splice |
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* code and be done with it. It can even allocate a new page if it needs to |
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* and swap that into the ring buffer. |
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* |
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* We will be using cmpxchg soon to make all this lockless. |
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* |
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*/ |
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|
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/* Used for individual buffers (after the counter) */ |
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#define RB_BUFFER_OFF (1 << 20) |
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|
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#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
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#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
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#define RB_ALIGNMENT 4U |
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#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
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#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
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#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS |
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# define RB_FORCE_8BYTE_ALIGNMENT 0 |
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# define RB_ARCH_ALIGNMENT RB_ALIGNMENT |
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#else |
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# define RB_FORCE_8BYTE_ALIGNMENT 1 |
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# define RB_ARCH_ALIGNMENT 8U |
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#endif |
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#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) |
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|
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/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
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#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX |
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enum { |
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RB_LEN_TIME_EXTEND = 8, |
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RB_LEN_TIME_STAMP = 8, |
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}; |
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#define skip_time_extend(event) \ |
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((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) |
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#define extended_time(event) \ |
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(event->type_len >= RINGBUF_TYPE_TIME_EXTEND) |
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|
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static inline int rb_null_event(struct ring_buffer_event *event) |
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{ |
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return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
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} |
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static void rb_event_set_padding(struct ring_buffer_event *event) |
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{ |
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/* padding has a NULL time_delta */ |
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event->type_len = RINGBUF_TYPE_PADDING; |
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event->time_delta = 0; |
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} |
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static unsigned |
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rb_event_data_length(struct ring_buffer_event *event) |
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{ |
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unsigned length; |
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if (event->type_len) |
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length = event->type_len * RB_ALIGNMENT; |
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else |
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length = event->array[0]; |
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return length + RB_EVNT_HDR_SIZE; |
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} |
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/* |
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* Return the length of the given event. Will return |
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* the length of the time extend if the event is a |
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* time extend. |
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*/ |
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static inline unsigned |
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rb_event_length(struct ring_buffer_event *event) |
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{ |
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switch (event->type_len) { |
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case RINGBUF_TYPE_PADDING: |
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if (rb_null_event(event)) |
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/* undefined */ |
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return -1; |
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return event->array[0] + RB_EVNT_HDR_SIZE; |
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|
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case RINGBUF_TYPE_TIME_EXTEND: |
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return RB_LEN_TIME_EXTEND; |
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case RINGBUF_TYPE_TIME_STAMP: |
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return RB_LEN_TIME_STAMP; |
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case RINGBUF_TYPE_DATA: |
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return rb_event_data_length(event); |
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default: |
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WARN_ON_ONCE(1); |
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} |
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/* not hit */ |
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return 0; |
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} |
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/* |
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* Return total length of time extend and data, |
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* or just the event length for all other events. |
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*/ |
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static inline unsigned |
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rb_event_ts_length(struct ring_buffer_event *event) |
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{ |
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unsigned len = 0; |
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|
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if (extended_time(event)) { |
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/* time extends include the data event after it */ |
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len = RB_LEN_TIME_EXTEND; |
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event = skip_time_extend(event); |
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} |
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return len + rb_event_length(event); |
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} |
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|
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/** |
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* ring_buffer_event_length - return the length of the event |
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* @event: the event to get the length of |
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* |
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* Returns the size of the data load of a data event. |
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* If the event is something other than a data event, it |
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* returns the size of the event itself. With the exception |
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* of a TIME EXTEND, where it still returns the size of the |
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* data load of the data event after it. |
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*/ |
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unsigned ring_buffer_event_length(struct ring_buffer_event *event) |
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{ |
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unsigned length; |
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if (extended_time(event)) |
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event = skip_time_extend(event); |
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length = rb_event_length(event); |
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if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
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return length; |
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length -= RB_EVNT_HDR_SIZE; |
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if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) |
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length -= sizeof(event->array[0]); |
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return length; |
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} |
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EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
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|
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/* inline for ring buffer fast paths */ |
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static __always_inline void * |
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rb_event_data(struct ring_buffer_event *event) |
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{ |
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if (extended_time(event)) |
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event = skip_time_extend(event); |
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WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
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/* If length is in len field, then array[0] has the data */ |
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if (event->type_len) |
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return (void *)&event->array[0]; |
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/* Otherwise length is in array[0] and array[1] has the data */ |
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return (void *)&event->array[1]; |
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} |
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/** |
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* ring_buffer_event_data - return the data of the event |
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* @event: the event to get the data from |
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*/ |
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void *ring_buffer_event_data(struct ring_buffer_event *event) |
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{ |
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return rb_event_data(event); |
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} |
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EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
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#define for_each_buffer_cpu(buffer, cpu) \ |
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for_each_cpu(cpu, buffer->cpumask) |
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#define for_each_online_buffer_cpu(buffer, cpu) \ |
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for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask) |
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#define TS_SHIFT 27 |
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#define TS_MASK ((1ULL << TS_SHIFT) - 1) |
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#define TS_DELTA_TEST (~TS_MASK) |
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/** |
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* ring_buffer_event_time_stamp - return the event's extended timestamp |
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* @event: the event to get the timestamp of |
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* |
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* Returns the extended timestamp associated with a data event. |
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* An extended time_stamp is a 64-bit timestamp represented |
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* internally in a special way that makes the best use of space |
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* contained within a ring buffer event. This function decodes |
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* it and maps it to a straight u64 value. |
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*/ |
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u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) |
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{ |
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u64 ts; |
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ts = event->array[0]; |
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ts <<= TS_SHIFT; |
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ts += event->time_delta; |
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return ts; |
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} |
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|
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/* Flag when events were overwritten */ |
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#define RB_MISSED_EVENTS (1 << 31) |
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/* Missed count stored at end */ |
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#define RB_MISSED_STORED (1 << 30) |
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struct buffer_data_page { |
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u64 time_stamp; /* page time stamp */ |
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local_t commit; /* write committed index */ |
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unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
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}; |
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/* |
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* Note, the buffer_page list must be first. The buffer pages |
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* are allocated in cache lines, which means that each buffer |
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* page will be at the beginning of a cache line, and thus |
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* the least significant bits will be zero. We use this to |
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* add flags in the list struct pointers, to make the ring buffer |
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* lockless. |
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*/ |
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struct buffer_page { |
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struct list_head list; /* list of buffer pages */ |
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local_t write; /* index for next write */ |
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unsigned read; /* index for next read */ |
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local_t entries; /* entries on this page */ |
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unsigned long real_end; /* real end of data */ |
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struct buffer_data_page *page; /* Actual data page */ |
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}; |
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/* |
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* The buffer page counters, write and entries, must be reset |
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* atomically when crossing page boundaries. To synchronize this |
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* update, two counters are inserted into the number. One is |
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* the actual counter for the write position or count on the page. |
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* |
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* The other is a counter of updaters. Before an update happens |
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* the update partition of the counter is incremented. This will |
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* allow the updater to update the counter atomically. |
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* |
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* The counter is 20 bits, and the state data is 12. |
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*/ |
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#define RB_WRITE_MASK 0xfffff |
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#define RB_WRITE_INTCNT (1 << 20) |
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static void rb_init_page(struct buffer_data_page *bpage) |
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{ |
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local_set(&bpage->commit, 0); |
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} |
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|
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/* |
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* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing |
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* this issue out. |
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*/ |
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static void free_buffer_page(struct buffer_page *bpage) |
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{ |
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free_page((unsigned long)bpage->page); |
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kfree(bpage); |
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} |
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|
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/* |
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* We need to fit the time_stamp delta into 27 bits. |
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*/ |
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static inline int test_time_stamp(u64 delta) |
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{ |
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if (delta & TS_DELTA_TEST) |
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return 1; |
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return 0; |
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} |
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#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
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|
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/* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
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#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) |
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int ring_buffer_print_page_header(struct trace_seq *s) |
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{ |
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struct buffer_data_page field; |
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trace_seq_printf(s, "\tfield: u64 timestamp;\t" |
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"offset:0;\tsize:%u;\tsigned:%u;\n", |
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(unsigned int)sizeof(field.time_stamp), |
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(unsigned int)is_signed_type(u64)); |
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trace_seq_printf(s, "\tfield: local_t commit;\t" |
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"offset:%u;\tsize:%u;\tsigned:%u;\n", |
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(unsigned int)offsetof(typeof(field), commit), |
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(unsigned int)sizeof(field.commit), |
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(unsigned int)is_signed_type(long)); |
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trace_seq_printf(s, "\tfield: int overwrite;\t" |
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"offset:%u;\tsize:%u;\tsigned:%u;\n", |
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(unsigned int)offsetof(typeof(field), commit), |
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1, |
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(unsigned int)is_signed_type(long)); |
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trace_seq_printf(s, "\tfield: char data;\t" |
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"offset:%u;\tsize:%u;\tsigned:%u;\n", |
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(unsigned int)offsetof(typeof(field), data), |
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(unsigned int)BUF_PAGE_SIZE, |
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(unsigned int)is_signed_type(char)); |
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|
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return !trace_seq_has_overflowed(s); |
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} |
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struct rb_irq_work { |
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struct irq_work work; |
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wait_queue_head_t waiters; |
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wait_queue_head_t full_waiters; |
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bool waiters_pending; |
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bool full_waiters_pending; |
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bool wakeup_full; |
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}; |
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|
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/* |
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* Structure to hold event state and handle nested events. |
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*/ |
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struct rb_event_info { |
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u64 ts; |
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u64 delta; |
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u64 before; |
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u64 after; |
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unsigned long length; |
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struct buffer_page *tail_page; |
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int add_timestamp; |
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}; |
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|
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/* |
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* Used for the add_timestamp |
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* NONE |
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* EXTEND - wants a time extend |
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* ABSOLUTE - the buffer requests all events to have absolute time stamps |
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* FORCE - force a full time stamp. |
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*/ |
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enum { |
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RB_ADD_STAMP_NONE = 0, |
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RB_ADD_STAMP_EXTEND = BIT(1), |
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RB_ADD_STAMP_ABSOLUTE = BIT(2), |
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RB_ADD_STAMP_FORCE = BIT(3) |
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}; |
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/* |
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* Used for which event context the event is in. |
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* TRANSITION = 0 |
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* NMI = 1 |
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* IRQ = 2 |
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* SOFTIRQ = 3 |
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* NORMAL = 4 |
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* |
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* See trace_recursive_lock() comment below for more details. |
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*/ |
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enum { |
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RB_CTX_TRANSITION, |
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RB_CTX_NMI, |
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RB_CTX_IRQ, |
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RB_CTX_SOFTIRQ, |
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RB_CTX_NORMAL, |
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RB_CTX_MAX |
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}; |
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|
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#if BITS_PER_LONG == 32 |
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#define RB_TIME_32 |
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#endif |
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|
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/* To test on 64 bit machines */ |
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//#define RB_TIME_32 |
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|
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#ifdef RB_TIME_32 |
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|
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struct rb_time_struct { |
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local_t cnt; |
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local_t top; |
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local_t bottom; |
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}; |
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#else |
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#include <asm/local64.h> |
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struct rb_time_struct { |
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local64_t time; |
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}; |
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#endif |
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typedef struct rb_time_struct rb_time_t; |
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|
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/* |
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* head_page == tail_page && head == tail then buffer is empty. |
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*/ |
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struct ring_buffer_per_cpu { |
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int cpu; |
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atomic_t record_disabled; |
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atomic_t resize_disabled; |
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struct trace_buffer *buffer; |
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raw_spinlock_t reader_lock; /* serialize readers */ |
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arch_spinlock_t lock; |
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struct lock_class_key lock_key; |
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struct buffer_data_page *free_page; |
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unsigned long nr_pages; |
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unsigned int current_context; |
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struct list_head *pages; |
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struct buffer_page *head_page; /* read from head */ |
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struct buffer_page *tail_page; /* write to tail */ |
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struct buffer_page *commit_page; /* committed pages */ |
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struct buffer_page *reader_page; |
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unsigned long lost_events; |
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unsigned long last_overrun; |
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unsigned long nest; |
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local_t entries_bytes; |
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local_t entries; |
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local_t overrun; |
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local_t commit_overrun; |
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local_t dropped_events; |
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local_t committing; |
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local_t commits; |
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local_t pages_touched; |
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local_t pages_read; |
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long last_pages_touch; |
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size_t shortest_full; |
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unsigned long read; |
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unsigned long read_bytes; |
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rb_time_t write_stamp; |
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rb_time_t before_stamp; |
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u64 read_stamp; |
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/* ring buffer pages to update, > 0 to add, < 0 to remove */ |
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long nr_pages_to_update; |
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struct list_head new_pages; /* new pages to add */ |
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struct work_struct update_pages_work; |
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struct completion update_done; |
|
|
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struct rb_irq_work irq_work; |
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}; |
|
|
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struct trace_buffer { |
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unsigned flags; |
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int cpus; |
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atomic_t record_disabled; |
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cpumask_var_t cpumask; |
|
|
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struct lock_class_key *reader_lock_key; |
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|
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struct mutex mutex; |
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|
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struct ring_buffer_per_cpu **buffers; |
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|
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struct hlist_node node; |
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u64 (*clock)(void); |
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|
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struct rb_irq_work irq_work; |
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bool time_stamp_abs; |
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}; |
|
|
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struct ring_buffer_iter { |
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struct ring_buffer_per_cpu *cpu_buffer; |
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unsigned long head; |
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unsigned long next_event; |
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struct buffer_page *head_page; |
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struct buffer_page *cache_reader_page; |
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unsigned long cache_read; |
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u64 read_stamp; |
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u64 page_stamp; |
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struct ring_buffer_event *event; |
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int missed_events; |
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}; |
|
|
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#ifdef RB_TIME_32 |
|
|
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/* |
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* On 32 bit machines, local64_t is very expensive. As the ring |
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* buffer doesn't need all the features of a true 64 bit atomic, |
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* on 32 bit, it uses these functions (64 still uses local64_t). |
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* |
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* For the ring buffer, 64 bit required operations for the time is |
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* the following: |
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* |
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* - Only need 59 bits (uses 60 to make it even). |
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* - Reads may fail if it interrupted a modification of the time stamp. |
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* It will succeed if it did not interrupt another write even if |
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* the read itself is interrupted by a write. |
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* It returns whether it was successful or not. |
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* |
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* - Writes always succeed and will overwrite other writes and writes |
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* that were done by events interrupting the current write. |
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* |
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* - A write followed by a read of the same time stamp will always succeed, |
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* but may not contain the same value. |
|
* |
|
* - A cmpxchg will fail if it interrupted another write or cmpxchg. |
|
* Other than that, it acts like a normal cmpxchg. |
|
* |
|
* The 60 bit time stamp is broken up by 30 bits in a top and bottom half |
|
* (bottom being the least significant 30 bits of the 60 bit time stamp). |
|
* |
|
* The two most significant bits of each half holds a 2 bit counter (0-3). |
|
* Each update will increment this counter by one. |
|
* When reading the top and bottom, if the two counter bits match then the |
|
* top and bottom together make a valid 60 bit number. |
|
*/ |
|
#define RB_TIME_SHIFT 30 |
|
#define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1) |
|
|
|
static inline int rb_time_cnt(unsigned long val) |
|
{ |
|
return (val >> RB_TIME_SHIFT) & 3; |
|
} |
|
|
|
static inline u64 rb_time_val(unsigned long top, unsigned long bottom) |
|
{ |
|
u64 val; |
|
|
|
val = top & RB_TIME_VAL_MASK; |
|
val <<= RB_TIME_SHIFT; |
|
val |= bottom & RB_TIME_VAL_MASK; |
|
|
|
return val; |
|
} |
|
|
|
static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt) |
|
{ |
|
unsigned long top, bottom; |
|
unsigned long c; |
|
|
|
/* |
|
* If the read is interrupted by a write, then the cnt will |
|
* be different. Loop until both top and bottom have been read |
|
* without interruption. |
|
*/ |
|
do { |
|
c = local_read(&t->cnt); |
|
top = local_read(&t->top); |
|
bottom = local_read(&t->bottom); |
|
} while (c != local_read(&t->cnt)); |
|
|
|
*cnt = rb_time_cnt(top); |
|
|
|
/* If top and bottom counts don't match, this interrupted a write */ |
|
if (*cnt != rb_time_cnt(bottom)) |
|
return false; |
|
|
|
*ret = rb_time_val(top, bottom); |
|
return true; |
|
} |
|
|
|
static bool rb_time_read(rb_time_t *t, u64 *ret) |
|
{ |
|
unsigned long cnt; |
|
|
|
return __rb_time_read(t, ret, &cnt); |
|
} |
|
|
|
static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt) |
|
{ |
|
return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT); |
|
} |
|
|
|
static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom) |
|
{ |
|
*top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK); |
|
*bottom = (unsigned long)(val & RB_TIME_VAL_MASK); |
|
} |
|
|
|
static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt) |
|
{ |
|
val = rb_time_val_cnt(val, cnt); |
|
local_set(t, val); |
|
} |
|
|
|
static void rb_time_set(rb_time_t *t, u64 val) |
|
{ |
|
unsigned long cnt, top, bottom; |
|
|
|
rb_time_split(val, &top, &bottom); |
|
|
|
/* Writes always succeed with a valid number even if it gets interrupted. */ |
|
do { |
|
cnt = local_inc_return(&t->cnt); |
|
rb_time_val_set(&t->top, top, cnt); |
|
rb_time_val_set(&t->bottom, bottom, cnt); |
|
} while (cnt != local_read(&t->cnt)); |
|
} |
|
|
|
static inline bool |
|
rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set) |
|
{ |
|
unsigned long ret; |
|
|
|
ret = local_cmpxchg(l, expect, set); |
|
return ret == expect; |
|
} |
|
|
|
static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) |
|
{ |
|
unsigned long cnt, top, bottom; |
|
unsigned long cnt2, top2, bottom2; |
|
u64 val; |
|
|
|
/* The cmpxchg always fails if it interrupted an update */ |
|
if (!__rb_time_read(t, &val, &cnt2)) |
|
return false; |
|
|
|
if (val != expect) |
|
return false; |
|
|
|
cnt = local_read(&t->cnt); |
|
if ((cnt & 3) != cnt2) |
|
return false; |
|
|
|
cnt2 = cnt + 1; |
|
|
|
rb_time_split(val, &top, &bottom); |
|
top = rb_time_val_cnt(top, cnt); |
|
bottom = rb_time_val_cnt(bottom, cnt); |
|
|
|
rb_time_split(set, &top2, &bottom2); |
|
top2 = rb_time_val_cnt(top2, cnt2); |
|
bottom2 = rb_time_val_cnt(bottom2, cnt2); |
|
|
|
if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2)) |
|
return false; |
|
if (!rb_time_read_cmpxchg(&t->top, top, top2)) |
|
return false; |
|
if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2)) |
|
return false; |
|
return true; |
|
} |
|
|
|
#else /* 64 bits */ |
|
|
|
/* local64_t always succeeds */ |
|
|
|
static inline bool rb_time_read(rb_time_t *t, u64 *ret) |
|
{ |
|
*ret = local64_read(&t->time); |
|
return true; |
|
} |
|
static void rb_time_set(rb_time_t *t, u64 val) |
|
{ |
|
local64_set(&t->time, val); |
|
} |
|
|
|
static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) |
|
{ |
|
u64 val; |
|
val = local64_cmpxchg(&t->time, expect, set); |
|
return val == expect; |
|
} |
|
#endif |
|
|
|
/** |
|
* ring_buffer_nr_pages - get the number of buffer pages in the ring buffer |
|
* @buffer: The ring_buffer to get the number of pages from |
|
* @cpu: The cpu of the ring_buffer to get the number of pages from |
|
* |
|
* Returns the number of pages used by a per_cpu buffer of the ring buffer. |
|
*/ |
|
size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu) |
|
{ |
|
return buffer->buffers[cpu]->nr_pages; |
|
} |
|
|
|
/** |
|
* ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer |
|
* @buffer: The ring_buffer to get the number of pages from |
|
* @cpu: The cpu of the ring_buffer to get the number of pages from |
|
* |
|
* Returns the number of pages that have content in the ring buffer. |
|
*/ |
|
size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu) |
|
{ |
|
size_t read; |
|
size_t cnt; |
|
|
|
read = local_read(&buffer->buffers[cpu]->pages_read); |
|
cnt = local_read(&buffer->buffers[cpu]->pages_touched); |
|
/* The reader can read an empty page, but not more than that */ |
|
if (cnt < read) { |
|
WARN_ON_ONCE(read > cnt + 1); |
|
return 0; |
|
} |
|
|
|
return cnt - read; |
|
} |
|
|
|
/* |
|
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input |
|
* |
|
* Schedules a delayed work to wake up any task that is blocked on the |
|
* ring buffer waiters queue. |
|
*/ |
|
static void rb_wake_up_waiters(struct irq_work *work) |
|
{ |
|
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); |
|
|
|
wake_up_all(&rbwork->waiters); |
|
if (rbwork->wakeup_full) { |
|
rbwork->wakeup_full = false; |
|
wake_up_all(&rbwork->full_waiters); |
|
} |
|
} |
|
|
|
/** |
|
* ring_buffer_wait - wait for input to the ring buffer |
|
* @buffer: buffer to wait on |
|
* @cpu: the cpu buffer to wait on |
|
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS |
|
* |
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
|
* as data is added to any of the @buffer's cpu buffers. Otherwise |
|
* it will wait for data to be added to a specific cpu buffer. |
|
*/ |
|
int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
DEFINE_WAIT(wait); |
|
struct rb_irq_work *work; |
|
int ret = 0; |
|
|
|
/* |
|
* Depending on what the caller is waiting for, either any |
|
* data in any cpu buffer, or a specific buffer, put the |
|
* caller on the appropriate wait queue. |
|
*/ |
|
if (cpu == RING_BUFFER_ALL_CPUS) { |
|
work = &buffer->irq_work; |
|
/* Full only makes sense on per cpu reads */ |
|
full = 0; |
|
} else { |
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return -ENODEV; |
|
cpu_buffer = buffer->buffers[cpu]; |
|
work = &cpu_buffer->irq_work; |
|
} |
|
|
|
|
|
while (true) { |
|
if (full) |
|
prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); |
|
else |
|
prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); |
|
|
|
/* |
|
* The events can happen in critical sections where |
|
* checking a work queue can cause deadlocks. |
|
* After adding a task to the queue, this flag is set |
|
* only to notify events to try to wake up the queue |
|
* using irq_work. |
|
* |
|
* We don't clear it even if the buffer is no longer |
|
* empty. The flag only causes the next event to run |
|
* irq_work to do the work queue wake up. The worse |
|
* that can happen if we race with !trace_empty() is that |
|
* an event will cause an irq_work to try to wake up |
|
* an empty queue. |
|
* |
|
* There's no reason to protect this flag either, as |
|
* the work queue and irq_work logic will do the necessary |
|
* synchronization for the wake ups. The only thing |
|
* that is necessary is that the wake up happens after |
|
* a task has been queued. It's OK for spurious wake ups. |
|
*/ |
|
if (full) |
|
work->full_waiters_pending = true; |
|
else |
|
work->waiters_pending = true; |
|
|
|
if (signal_pending(current)) { |
|
ret = -EINTR; |
|
break; |
|
} |
|
|
|
if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) |
|
break; |
|
|
|
if (cpu != RING_BUFFER_ALL_CPUS && |
|
!ring_buffer_empty_cpu(buffer, cpu)) { |
|
unsigned long flags; |
|
bool pagebusy; |
|
size_t nr_pages; |
|
size_t dirty; |
|
|
|
if (!full) |
|
break; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; |
|
nr_pages = cpu_buffer->nr_pages; |
|
dirty = ring_buffer_nr_dirty_pages(buffer, cpu); |
|
if (!cpu_buffer->shortest_full || |
|
cpu_buffer->shortest_full < full) |
|
cpu_buffer->shortest_full = full; |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
if (!pagebusy && |
|
(!nr_pages || (dirty * 100) > full * nr_pages)) |
|
break; |
|
} |
|
|
|
schedule(); |
|
} |
|
|
|
if (full) |
|
finish_wait(&work->full_waiters, &wait); |
|
else |
|
finish_wait(&work->waiters, &wait); |
|
|
|
return ret; |
|
} |
|
|
|
/** |
|
* ring_buffer_poll_wait - poll on buffer input |
|
* @buffer: buffer to wait on |
|
* @cpu: the cpu buffer to wait on |
|
* @filp: the file descriptor |
|
* @poll_table: The poll descriptor |
|
* |
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
|
* as data is added to any of the @buffer's cpu buffers. Otherwise |
|
* it will wait for data to be added to a specific cpu buffer. |
|
* |
|
* Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, |
|
* zero otherwise. |
|
*/ |
|
__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu, |
|
struct file *filp, poll_table *poll_table) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct rb_irq_work *work; |
|
|
|
if (cpu == RING_BUFFER_ALL_CPUS) |
|
work = &buffer->irq_work; |
|
else { |
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return -EINVAL; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
work = &cpu_buffer->irq_work; |
|
} |
|
|
|
poll_wait(filp, &work->waiters, poll_table); |
|
work->waiters_pending = true; |
|
/* |
|
* There's a tight race between setting the waiters_pending and |
|
* checking if the ring buffer is empty. Once the waiters_pending bit |
|
* is set, the next event will wake the task up, but we can get stuck |
|
* if there's only a single event in. |
|
* |
|
* FIXME: Ideally, we need a memory barrier on the writer side as well, |
|
* but adding a memory barrier to all events will cause too much of a |
|
* performance hit in the fast path. We only need a memory barrier when |
|
* the buffer goes from empty to having content. But as this race is |
|
* extremely small, and it's not a problem if another event comes in, we |
|
* will fix it later. |
|
*/ |
|
smp_mb(); |
|
|
|
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || |
|
(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) |
|
return EPOLLIN | EPOLLRDNORM; |
|
return 0; |
|
} |
|
|
|
/* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
|
#define RB_WARN_ON(b, cond) \ |
|
({ \ |
|
int _____ret = unlikely(cond); \ |
|
if (_____ret) { \ |
|
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ |
|
struct ring_buffer_per_cpu *__b = \ |
|
(void *)b; \ |
|
atomic_inc(&__b->buffer->record_disabled); \ |
|
} else \ |
|
atomic_inc(&b->record_disabled); \ |
|
WARN_ON(1); \ |
|
} \ |
|
_____ret; \ |
|
}) |
|
|
|
/* Up this if you want to test the TIME_EXTENTS and normalization */ |
|
#define DEBUG_SHIFT 0 |
|
|
|
static inline u64 rb_time_stamp(struct trace_buffer *buffer) |
|
{ |
|
u64 ts; |
|
|
|
/* Skip retpolines :-( */ |
|
if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local)) |
|
ts = trace_clock_local(); |
|
else |
|
ts = buffer->clock(); |
|
|
|
/* shift to debug/test normalization and TIME_EXTENTS */ |
|
return ts << DEBUG_SHIFT; |
|
} |
|
|
|
u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu) |
|
{ |
|
u64 time; |
|
|
|
preempt_disable_notrace(); |
|
time = rb_time_stamp(buffer); |
|
preempt_enable_notrace(); |
|
|
|
return time; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); |
|
|
|
void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer, |
|
int cpu, u64 *ts) |
|
{ |
|
/* Just stupid testing the normalize function and deltas */ |
|
*ts >>= DEBUG_SHIFT; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); |
|
|
|
/* |
|
* Making the ring buffer lockless makes things tricky. |
|
* Although writes only happen on the CPU that they are on, |
|
* and they only need to worry about interrupts. Reads can |
|
* happen on any CPU. |
|
* |
|
* The reader page is always off the ring buffer, but when the |
|
* reader finishes with a page, it needs to swap its page with |
|
* a new one from the buffer. The reader needs to take from |
|
* the head (writes go to the tail). But if a writer is in overwrite |
|
* mode and wraps, it must push the head page forward. |
|
* |
|
* Here lies the problem. |
|
* |
|
* The reader must be careful to replace only the head page, and |
|
* not another one. As described at the top of the file in the |
|
* ASCII art, the reader sets its old page to point to the next |
|
* page after head. It then sets the page after head to point to |
|
* the old reader page. But if the writer moves the head page |
|
* during this operation, the reader could end up with the tail. |
|
* |
|
* We use cmpxchg to help prevent this race. We also do something |
|
* special with the page before head. We set the LSB to 1. |
|
* |
|
* When the writer must push the page forward, it will clear the |
|
* bit that points to the head page, move the head, and then set |
|
* the bit that points to the new head page. |
|
* |
|
* We also don't want an interrupt coming in and moving the head |
|
* page on another writer. Thus we use the second LSB to catch |
|
* that too. Thus: |
|
* |
|
* head->list->prev->next bit 1 bit 0 |
|
* ------- ------- |
|
* Normal page 0 0 |
|
* Points to head page 0 1 |
|
* New head page 1 0 |
|
* |
|
* Note we can not trust the prev pointer of the head page, because: |
|
* |
|
* +----+ +-----+ +-----+ |
|
* | |------>| T |---X--->| N | |
|
* | |<------| | | | |
|
* +----+ +-----+ +-----+ |
|
* ^ ^ | |
|
* | +-----+ | | |
|
* +----------| R |----------+ | |
|
* | |<-----------+ |
|
* +-----+ |
|
* |
|
* Key: ---X--> HEAD flag set in pointer |
|
* T Tail page |
|
* R Reader page |
|
* N Next page |
|
* |
|
* (see __rb_reserve_next() to see where this happens) |
|
* |
|
* What the above shows is that the reader just swapped out |
|
* the reader page with a page in the buffer, but before it |
|
* could make the new header point back to the new page added |
|
* it was preempted by a writer. The writer moved forward onto |
|
* the new page added by the reader and is about to move forward |
|
* again. |
|
* |
|
* You can see, it is legitimate for the previous pointer of |
|
* the head (or any page) not to point back to itself. But only |
|
* temporarily. |
|
*/ |
|
|
|
#define RB_PAGE_NORMAL 0UL |
|
#define RB_PAGE_HEAD 1UL |
|
#define RB_PAGE_UPDATE 2UL |
|
|
|
|
|
#define RB_FLAG_MASK 3UL |
|
|
|
/* PAGE_MOVED is not part of the mask */ |
|
#define RB_PAGE_MOVED 4UL |
|
|
|
/* |
|
* rb_list_head - remove any bit |
|
*/ |
|
static struct list_head *rb_list_head(struct list_head *list) |
|
{ |
|
unsigned long val = (unsigned long)list; |
|
|
|
return (struct list_head *)(val & ~RB_FLAG_MASK); |
|
} |
|
|
|
/* |
|
* rb_is_head_page - test if the given page is the head page |
|
* |
|
* Because the reader may move the head_page pointer, we can |
|
* not trust what the head page is (it may be pointing to |
|
* the reader page). But if the next page is a header page, |
|
* its flags will be non zero. |
|
*/ |
|
static inline int |
|
rb_is_head_page(struct buffer_page *page, struct list_head *list) |
|
{ |
|
unsigned long val; |
|
|
|
val = (unsigned long)list->next; |
|
|
|
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) |
|
return RB_PAGE_MOVED; |
|
|
|
return val & RB_FLAG_MASK; |
|
} |
|
|
|
/* |
|
* rb_is_reader_page |
|
* |
|
* The unique thing about the reader page, is that, if the |
|
* writer is ever on it, the previous pointer never points |
|
* back to the reader page. |
|
*/ |
|
static bool rb_is_reader_page(struct buffer_page *page) |
|
{ |
|
struct list_head *list = page->list.prev; |
|
|
|
return rb_list_head(list->next) != &page->list; |
|
} |
|
|
|
/* |
|
* rb_set_list_to_head - set a list_head to be pointing to head. |
|
*/ |
|
static void rb_set_list_to_head(struct list_head *list) |
|
{ |
|
unsigned long *ptr; |
|
|
|
ptr = (unsigned long *)&list->next; |
|
*ptr |= RB_PAGE_HEAD; |
|
*ptr &= ~RB_PAGE_UPDATE; |
|
} |
|
|
|
/* |
|
* rb_head_page_activate - sets up head page |
|
*/ |
|
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct buffer_page *head; |
|
|
|
head = cpu_buffer->head_page; |
|
if (!head) |
|
return; |
|
|
|
/* |
|
* Set the previous list pointer to have the HEAD flag. |
|
*/ |
|
rb_set_list_to_head(head->list.prev); |
|
} |
|
|
|
static void rb_list_head_clear(struct list_head *list) |
|
{ |
|
unsigned long *ptr = (unsigned long *)&list->next; |
|
|
|
*ptr &= ~RB_FLAG_MASK; |
|
} |
|
|
|
/* |
|
* rb_head_page_deactivate - clears head page ptr (for free list) |
|
*/ |
|
static void |
|
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct list_head *hd; |
|
|
|
/* Go through the whole list and clear any pointers found. */ |
|
rb_list_head_clear(cpu_buffer->pages); |
|
|
|
list_for_each(hd, cpu_buffer->pages) |
|
rb_list_head_clear(hd); |
|
} |
|
|
|
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *head, |
|
struct buffer_page *prev, |
|
int old_flag, int new_flag) |
|
{ |
|
struct list_head *list; |
|
unsigned long val = (unsigned long)&head->list; |
|
unsigned long ret; |
|
|
|
list = &prev->list; |
|
|
|
val &= ~RB_FLAG_MASK; |
|
|
|
ret = cmpxchg((unsigned long *)&list->next, |
|
val | old_flag, val | new_flag); |
|
|
|
/* check if the reader took the page */ |
|
if ((ret & ~RB_FLAG_MASK) != val) |
|
return RB_PAGE_MOVED; |
|
|
|
return ret & RB_FLAG_MASK; |
|
} |
|
|
|
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *head, |
|
struct buffer_page *prev, |
|
int old_flag) |
|
{ |
|
return rb_head_page_set(cpu_buffer, head, prev, |
|
old_flag, RB_PAGE_UPDATE); |
|
} |
|
|
|
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *head, |
|
struct buffer_page *prev, |
|
int old_flag) |
|
{ |
|
return rb_head_page_set(cpu_buffer, head, prev, |
|
old_flag, RB_PAGE_HEAD); |
|
} |
|
|
|
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *head, |
|
struct buffer_page *prev, |
|
int old_flag) |
|
{ |
|
return rb_head_page_set(cpu_buffer, head, prev, |
|
old_flag, RB_PAGE_NORMAL); |
|
} |
|
|
|
static inline void rb_inc_page(struct buffer_page **bpage) |
|
{ |
|
struct list_head *p = rb_list_head((*bpage)->list.next); |
|
|
|
*bpage = list_entry(p, struct buffer_page, list); |
|
} |
|
|
|
static struct buffer_page * |
|
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct buffer_page *head; |
|
struct buffer_page *page; |
|
struct list_head *list; |
|
int i; |
|
|
|
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) |
|
return NULL; |
|
|
|
/* sanity check */ |
|
list = cpu_buffer->pages; |
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) |
|
return NULL; |
|
|
|
page = head = cpu_buffer->head_page; |
|
/* |
|
* It is possible that the writer moves the header behind |
|
* where we started, and we miss in one loop. |
|
* A second loop should grab the header, but we'll do |
|
* three loops just because I'm paranoid. |
|
*/ |
|
for (i = 0; i < 3; i++) { |
|
do { |
|
if (rb_is_head_page(page, page->list.prev)) { |
|
cpu_buffer->head_page = page; |
|
return page; |
|
} |
|
rb_inc_page(&page); |
|
} while (page != head); |
|
} |
|
|
|
RB_WARN_ON(cpu_buffer, 1); |
|
|
|
return NULL; |
|
} |
|
|
|
static int rb_head_page_replace(struct buffer_page *old, |
|
struct buffer_page *new) |
|
{ |
|
unsigned long *ptr = (unsigned long *)&old->list.prev->next; |
|
unsigned long val; |
|
unsigned long ret; |
|
|
|
val = *ptr & ~RB_FLAG_MASK; |
|
val |= RB_PAGE_HEAD; |
|
|
|
ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
|
|
|
return ret == val; |
|
} |
|
|
|
/* |
|
* rb_tail_page_update - move the tail page forward |
|
*/ |
|
static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *tail_page, |
|
struct buffer_page *next_page) |
|
{ |
|
unsigned long old_entries; |
|
unsigned long old_write; |
|
|
|
/* |
|
* The tail page now needs to be moved forward. |
|
* |
|
* We need to reset the tail page, but without messing |
|
* with possible erasing of data brought in by interrupts |
|
* that have moved the tail page and are currently on it. |
|
* |
|
* We add a counter to the write field to denote this. |
|
*/ |
|
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); |
|
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); |
|
|
|
local_inc(&cpu_buffer->pages_touched); |
|
/* |
|
* Just make sure we have seen our old_write and synchronize |
|
* with any interrupts that come in. |
|
*/ |
|
barrier(); |
|
|
|
/* |
|
* If the tail page is still the same as what we think |
|
* it is, then it is up to us to update the tail |
|
* pointer. |
|
*/ |
|
if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { |
|
/* Zero the write counter */ |
|
unsigned long val = old_write & ~RB_WRITE_MASK; |
|
unsigned long eval = old_entries & ~RB_WRITE_MASK; |
|
|
|
/* |
|
* This will only succeed if an interrupt did |
|
* not come in and change it. In which case, we |
|
* do not want to modify it. |
|
* |
|
* We add (void) to let the compiler know that we do not care |
|
* about the return value of these functions. We use the |
|
* cmpxchg to only update if an interrupt did not already |
|
* do it for us. If the cmpxchg fails, we don't care. |
|
*/ |
|
(void)local_cmpxchg(&next_page->write, old_write, val); |
|
(void)local_cmpxchg(&next_page->entries, old_entries, eval); |
|
|
|
/* |
|
* No need to worry about races with clearing out the commit. |
|
* it only can increment when a commit takes place. But that |
|
* only happens in the outer most nested commit. |
|
*/ |
|
local_set(&next_page->page->commit, 0); |
|
|
|
/* Again, either we update tail_page or an interrupt does */ |
|
(void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); |
|
} |
|
} |
|
|
|
static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *bpage) |
|
{ |
|
unsigned long val = (unsigned long)bpage; |
|
|
|
if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) |
|
return 1; |
|
|
|
return 0; |
|
} |
|
|
|
/** |
|
* rb_check_list - make sure a pointer to a list has the last bits zero |
|
*/ |
|
static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct list_head *list) |
|
{ |
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) |
|
return 1; |
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) |
|
return 1; |
|
return 0; |
|
} |
|
|
|
/** |
|
* rb_check_pages - integrity check of buffer pages |
|
* @cpu_buffer: CPU buffer with pages to test |
|
* |
|
* As a safety measure we check to make sure the data pages have not |
|
* been corrupted. |
|
*/ |
|
static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct list_head *head = cpu_buffer->pages; |
|
struct buffer_page *bpage, *tmp; |
|
|
|
/* Reset the head page if it exists */ |
|
if (cpu_buffer->head_page) |
|
rb_set_head_page(cpu_buffer); |
|
|
|
rb_head_page_deactivate(cpu_buffer); |
|
|
|
if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
|
return -1; |
|
if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) |
|
return -1; |
|
|
|
if (rb_check_list(cpu_buffer, head)) |
|
return -1; |
|
|
|
list_for_each_entry_safe(bpage, tmp, head, list) { |
|
if (RB_WARN_ON(cpu_buffer, |
|
bpage->list.next->prev != &bpage->list)) |
|
return -1; |
|
if (RB_WARN_ON(cpu_buffer, |
|
bpage->list.prev->next != &bpage->list)) |
|
return -1; |
|
if (rb_check_list(cpu_buffer, &bpage->list)) |
|
return -1; |
|
} |
|
|
|
rb_head_page_activate(cpu_buffer); |
|
|
|
return 0; |
|
} |
|
|
|
static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
|
long nr_pages, struct list_head *pages) |
|
{ |
|
struct buffer_page *bpage, *tmp; |
|
bool user_thread = current->mm != NULL; |
|
gfp_t mflags; |
|
long i; |
|
|
|
/* |
|
* Check if the available memory is there first. |
|
* Note, si_mem_available() only gives us a rough estimate of available |
|
* memory. It may not be accurate. But we don't care, we just want |
|
* to prevent doing any allocation when it is obvious that it is |
|
* not going to succeed. |
|
*/ |
|
i = si_mem_available(); |
|
if (i < nr_pages) |
|
return -ENOMEM; |
|
|
|
/* |
|
* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails |
|
* gracefully without invoking oom-killer and the system is not |
|
* destabilized. |
|
*/ |
|
mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; |
|
|
|
/* |
|
* If a user thread allocates too much, and si_mem_available() |
|
* reports there's enough memory, even though there is not. |
|
* Make sure the OOM killer kills this thread. This can happen |
|
* even with RETRY_MAYFAIL because another task may be doing |
|
* an allocation after this task has taken all memory. |
|
* This is the task the OOM killer needs to take out during this |
|
* loop, even if it was triggered by an allocation somewhere else. |
|
*/ |
|
if (user_thread) |
|
set_current_oom_origin(); |
|
for (i = 0; i < nr_pages; i++) { |
|
struct page *page; |
|
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
|
mflags, cpu_to_node(cpu_buffer->cpu)); |
|
if (!bpage) |
|
goto free_pages; |
|
|
|
rb_check_bpage(cpu_buffer, bpage); |
|
|
|
list_add(&bpage->list, pages); |
|
|
|
page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0); |
|
if (!page) |
|
goto free_pages; |
|
bpage->page = page_address(page); |
|
rb_init_page(bpage->page); |
|
|
|
if (user_thread && fatal_signal_pending(current)) |
|
goto free_pages; |
|
} |
|
if (user_thread) |
|
clear_current_oom_origin(); |
|
|
|
return 0; |
|
|
|
free_pages: |
|
list_for_each_entry_safe(bpage, tmp, pages, list) { |
|
list_del_init(&bpage->list); |
|
free_buffer_page(bpage); |
|
} |
|
if (user_thread) |
|
clear_current_oom_origin(); |
|
|
|
return -ENOMEM; |
|
} |
|
|
|
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
|
unsigned long nr_pages) |
|
{ |
|
LIST_HEAD(pages); |
|
|
|
WARN_ON(!nr_pages); |
|
|
|
if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages)) |
|
return -ENOMEM; |
|
|
|
/* |
|
* The ring buffer page list is a circular list that does not |
|
* start and end with a list head. All page list items point to |
|
* other pages. |
|
*/ |
|
cpu_buffer->pages = pages.next; |
|
list_del(&pages); |
|
|
|
cpu_buffer->nr_pages = nr_pages; |
|
|
|
rb_check_pages(cpu_buffer); |
|
|
|
return 0; |
|
} |
|
|
|
static struct ring_buffer_per_cpu * |
|
rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct buffer_page *bpage; |
|
struct page *page; |
|
int ret; |
|
|
|
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), |
|
GFP_KERNEL, cpu_to_node(cpu)); |
|
if (!cpu_buffer) |
|
return NULL; |
|
|
|
cpu_buffer->cpu = cpu; |
|
cpu_buffer->buffer = buffer; |
|
raw_spin_lock_init(&cpu_buffer->reader_lock); |
|
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
|
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
|
INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
|
init_completion(&cpu_buffer->update_done); |
|
init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
|
init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
|
init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
|
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
|
GFP_KERNEL, cpu_to_node(cpu)); |
|
if (!bpage) |
|
goto fail_free_buffer; |
|
|
|
rb_check_bpage(cpu_buffer, bpage); |
|
|
|
cpu_buffer->reader_page = bpage; |
|
page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
|
if (!page) |
|
goto fail_free_reader; |
|
bpage->page = page_address(page); |
|
rb_init_page(bpage->page); |
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
|
INIT_LIST_HEAD(&cpu_buffer->new_pages); |
|
|
|
ret = rb_allocate_pages(cpu_buffer, nr_pages); |
|
if (ret < 0) |
|
goto fail_free_reader; |
|
|
|
cpu_buffer->head_page |
|
= list_entry(cpu_buffer->pages, struct buffer_page, list); |
|
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
|
|
|
rb_head_page_activate(cpu_buffer); |
|
|
|
return cpu_buffer; |
|
|
|
fail_free_reader: |
|
free_buffer_page(cpu_buffer->reader_page); |
|
|
|
fail_free_buffer: |
|
kfree(cpu_buffer); |
|
return NULL; |
|
} |
|
|
|
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct list_head *head = cpu_buffer->pages; |
|
struct buffer_page *bpage, *tmp; |
|
|
|
free_buffer_page(cpu_buffer->reader_page); |
|
|
|
rb_head_page_deactivate(cpu_buffer); |
|
|
|
if (head) { |
|
list_for_each_entry_safe(bpage, tmp, head, list) { |
|
list_del_init(&bpage->list); |
|
free_buffer_page(bpage); |
|
} |
|
bpage = list_entry(head, struct buffer_page, list); |
|
free_buffer_page(bpage); |
|
} |
|
|
|
kfree(cpu_buffer); |
|
} |
|
|
|
/** |
|
* __ring_buffer_alloc - allocate a new ring_buffer |
|
* @size: the size in bytes per cpu that is needed. |
|
* @flags: attributes to set for the ring buffer. |
|
* @key: ring buffer reader_lock_key. |
|
* |
|
* Currently the only flag that is available is the RB_FL_OVERWRITE |
|
* flag. This flag means that the buffer will overwrite old data |
|
* when the buffer wraps. If this flag is not set, the buffer will |
|
* drop data when the tail hits the head. |
|
*/ |
|
struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
|
struct lock_class_key *key) |
|
{ |
|
struct trace_buffer *buffer; |
|
long nr_pages; |
|
int bsize; |
|
int cpu; |
|
int ret; |
|
|
|
/* keep it in its own cache line */ |
|
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), |
|
GFP_KERNEL); |
|
if (!buffer) |
|
return NULL; |
|
|
|
if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
|
goto fail_free_buffer; |
|
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
|
buffer->flags = flags; |
|
buffer->clock = trace_clock_local; |
|
buffer->reader_lock_key = key; |
|
|
|
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
|
init_waitqueue_head(&buffer->irq_work.waiters); |
|
|
|
/* need at least two pages */ |
|
if (nr_pages < 2) |
|
nr_pages = 2; |
|
|
|
buffer->cpus = nr_cpu_ids; |
|
|
|
bsize = sizeof(void *) * nr_cpu_ids; |
|
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), |
|
GFP_KERNEL); |
|
if (!buffer->buffers) |
|
goto fail_free_cpumask; |
|
|
|
cpu = raw_smp_processor_id(); |
|
cpumask_set_cpu(cpu, buffer->cpumask); |
|
buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
|
if (!buffer->buffers[cpu]) |
|
goto fail_free_buffers; |
|
|
|
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
|
if (ret < 0) |
|
goto fail_free_buffers; |
|
|
|
mutex_init(&buffer->mutex); |
|
|
|
return buffer; |
|
|
|
fail_free_buffers: |
|
for_each_buffer_cpu(buffer, cpu) { |
|
if (buffer->buffers[cpu]) |
|
rb_free_cpu_buffer(buffer->buffers[cpu]); |
|
} |
|
kfree(buffer->buffers); |
|
|
|
fail_free_cpumask: |
|
free_cpumask_var(buffer->cpumask); |
|
|
|
fail_free_buffer: |
|
kfree(buffer); |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
|
|
|
/** |
|
* ring_buffer_free - free a ring buffer. |
|
* @buffer: the buffer to free. |
|
*/ |
|
void |
|
ring_buffer_free(struct trace_buffer *buffer) |
|
{ |
|
int cpu; |
|
|
|
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
|
|
|
for_each_buffer_cpu(buffer, cpu) |
|
rb_free_cpu_buffer(buffer->buffers[cpu]); |
|
|
|
kfree(buffer->buffers); |
|
free_cpumask_var(buffer->cpumask); |
|
|
|
kfree(buffer); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_free); |
|
|
|
void ring_buffer_set_clock(struct trace_buffer *buffer, |
|
u64 (*clock)(void)) |
|
{ |
|
buffer->clock = clock; |
|
} |
|
|
|
void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs) |
|
{ |
|
buffer->time_stamp_abs = abs; |
|
} |
|
|
|
bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer) |
|
{ |
|
return buffer->time_stamp_abs; |
|
} |
|
|
|
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
|
|
|
static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
|
{ |
|
return local_read(&bpage->entries) & RB_WRITE_MASK; |
|
} |
|
|
|
static inline unsigned long rb_page_write(struct buffer_page *bpage) |
|
{ |
|
return local_read(&bpage->write) & RB_WRITE_MASK; |
|
} |
|
|
|
static int |
|
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) |
|
{ |
|
struct list_head *tail_page, *to_remove, *next_page; |
|
struct buffer_page *to_remove_page, *tmp_iter_page; |
|
struct buffer_page *last_page, *first_page; |
|
unsigned long nr_removed; |
|
unsigned long head_bit; |
|
int page_entries; |
|
|
|
head_bit = 0; |
|
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock); |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
/* |
|
* We don't race with the readers since we have acquired the reader |
|
* lock. We also don't race with writers after disabling recording. |
|
* This makes it easy to figure out the first and the last page to be |
|
* removed from the list. We unlink all the pages in between including |
|
* the first and last pages. This is done in a busy loop so that we |
|
* lose the least number of traces. |
|
* The pages are freed after we restart recording and unlock readers. |
|
*/ |
|
tail_page = &cpu_buffer->tail_page->list; |
|
|
|
/* |
|
* tail page might be on reader page, we remove the next page |
|
* from the ring buffer |
|
*/ |
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
|
tail_page = rb_list_head(tail_page->next); |
|
to_remove = tail_page; |
|
|
|
/* start of pages to remove */ |
|
first_page = list_entry(rb_list_head(to_remove->next), |
|
struct buffer_page, list); |
|
|
|
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { |
|
to_remove = rb_list_head(to_remove)->next; |
|
head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; |
|
} |
|
|
|
next_page = rb_list_head(to_remove)->next; |
|
|
|
/* |
|
* Now we remove all pages between tail_page and next_page. |
|
* Make sure that we have head_bit value preserved for the |
|
* next page |
|
*/ |
|
tail_page->next = (struct list_head *)((unsigned long)next_page | |
|
head_bit); |
|
next_page = rb_list_head(next_page); |
|
next_page->prev = tail_page; |
|
|
|
/* make sure pages points to a valid page in the ring buffer */ |
|
cpu_buffer->pages = next_page; |
|
|
|
/* update head page */ |
|
if (head_bit) |
|
cpu_buffer->head_page = list_entry(next_page, |
|
struct buffer_page, list); |
|
|
|
/* |
|
* change read pointer to make sure any read iterators reset |
|
* themselves |
|
*/ |
|
cpu_buffer->read = 0; |
|
|
|
/* pages are removed, resume tracing and then free the pages */ |
|
atomic_dec(&cpu_buffer->record_disabled); |
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
|
|
|
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); |
|
|
|
/* last buffer page to remove */ |
|
last_page = list_entry(rb_list_head(to_remove), struct buffer_page, |
|
list); |
|
tmp_iter_page = first_page; |
|
|
|
do { |
|
cond_resched(); |
|
|
|
to_remove_page = tmp_iter_page; |
|
rb_inc_page(&tmp_iter_page); |
|
|
|
/* update the counters */ |
|
page_entries = rb_page_entries(to_remove_page); |
|
if (page_entries) { |
|
/* |
|
* If something was added to this page, it was full |
|
* since it is not the tail page. So we deduct the |
|
* bytes consumed in ring buffer from here. |
|
* Increment overrun to account for the lost events. |
|
*/ |
|
local_add(page_entries, &cpu_buffer->overrun); |
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
|
} |
|
|
|
/* |
|
* We have already removed references to this list item, just |
|
* free up the buffer_page and its page |
|
*/ |
|
free_buffer_page(to_remove_page); |
|
nr_removed--; |
|
|
|
} while (to_remove_page != last_page); |
|
|
|
RB_WARN_ON(cpu_buffer, nr_removed); |
|
|
|
return nr_removed == 0; |
|
} |
|
|
|
static int |
|
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct list_head *pages = &cpu_buffer->new_pages; |
|
int retries, success; |
|
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock); |
|
/* |
|
* We are holding the reader lock, so the reader page won't be swapped |
|
* in the ring buffer. Now we are racing with the writer trying to |
|
* move head page and the tail page. |
|
* We are going to adapt the reader page update process where: |
|
* 1. We first splice the start and end of list of new pages between |
|
* the head page and its previous page. |
|
* 2. We cmpxchg the prev_page->next to point from head page to the |
|
* start of new pages list. |
|
* 3. Finally, we update the head->prev to the end of new list. |
|
* |
|
* We will try this process 10 times, to make sure that we don't keep |
|
* spinning. |
|
*/ |
|
retries = 10; |
|
success = 0; |
|
while (retries--) { |
|
struct list_head *head_page, *prev_page, *r; |
|
struct list_head *last_page, *first_page; |
|
struct list_head *head_page_with_bit; |
|
|
|
head_page = &rb_set_head_page(cpu_buffer)->list; |
|
if (!head_page) |
|
break; |
|
prev_page = head_page->prev; |
|
|
|
first_page = pages->next; |
|
last_page = pages->prev; |
|
|
|
head_page_with_bit = (struct list_head *) |
|
((unsigned long)head_page | RB_PAGE_HEAD); |
|
|
|
last_page->next = head_page_with_bit; |
|
first_page->prev = prev_page; |
|
|
|
r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); |
|
|
|
if (r == head_page_with_bit) { |
|
/* |
|
* yay, we replaced the page pointer to our new list, |
|
* now, we just have to update to head page's prev |
|
* pointer to point to end of list |
|
*/ |
|
head_page->prev = last_page; |
|
success = 1; |
|
break; |
|
} |
|
} |
|
|
|
if (success) |
|
INIT_LIST_HEAD(pages); |
|
/* |
|
* If we weren't successful in adding in new pages, warn and stop |
|
* tracing |
|
*/ |
|
RB_WARN_ON(cpu_buffer, !success); |
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
|
|
|
/* free pages if they weren't inserted */ |
|
if (!success) { |
|
struct buffer_page *bpage, *tmp; |
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
|
list) { |
|
list_del_init(&bpage->list); |
|
free_buffer_page(bpage); |
|
} |
|
} |
|
return success; |
|
} |
|
|
|
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
int success; |
|
|
|
if (cpu_buffer->nr_pages_to_update > 0) |
|
success = rb_insert_pages(cpu_buffer); |
|
else |
|
success = rb_remove_pages(cpu_buffer, |
|
-cpu_buffer->nr_pages_to_update); |
|
|
|
if (success) |
|
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; |
|
} |
|
|
|
static void update_pages_handler(struct work_struct *work) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = container_of(work, |
|
struct ring_buffer_per_cpu, update_pages_work); |
|
rb_update_pages(cpu_buffer); |
|
complete(&cpu_buffer->update_done); |
|
} |
|
|
|
/** |
|
* ring_buffer_resize - resize the ring buffer |
|
* @buffer: the buffer to resize. |
|
* @size: the new size. |
|
* @cpu_id: the cpu buffer to resize |
|
* |
|
* Minimum size is 2 * BUF_PAGE_SIZE. |
|
* |
|
* Returns 0 on success and < 0 on failure. |
|
*/ |
|
int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, |
|
int cpu_id) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long nr_pages; |
|
int cpu, err; |
|
|
|
/* |
|
* Always succeed at resizing a non-existent buffer: |
|
*/ |
|
if (!buffer) |
|
return 0; |
|
|
|
/* Make sure the requested buffer exists */ |
|
if (cpu_id != RING_BUFFER_ALL_CPUS && |
|
!cpumask_test_cpu(cpu_id, buffer->cpumask)) |
|
return 0; |
|
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
|
|
|
/* we need a minimum of two pages */ |
|
if (nr_pages < 2) |
|
nr_pages = 2; |
|
|
|
/* prevent another thread from changing buffer sizes */ |
|
mutex_lock(&buffer->mutex); |
|
|
|
|
|
if (cpu_id == RING_BUFFER_ALL_CPUS) { |
|
/* |
|
* Don't succeed if resizing is disabled, as a reader might be |
|
* manipulating the ring buffer and is expecting a sane state while |
|
* this is true. |
|
*/ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
if (atomic_read(&cpu_buffer->resize_disabled)) { |
|
err = -EBUSY; |
|
goto out_err_unlock; |
|
} |
|
} |
|
|
|
/* calculate the pages to update */ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages - |
|
cpu_buffer->nr_pages; |
|
/* |
|
* nothing more to do for removing pages or no update |
|
*/ |
|
if (cpu_buffer->nr_pages_to_update <= 0) |
|
continue; |
|
/* |
|
* to add pages, make sure all new pages can be |
|
* allocated without receiving ENOMEM |
|
*/ |
|
INIT_LIST_HEAD(&cpu_buffer->new_pages); |
|
if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, |
|
&cpu_buffer->new_pages)) { |
|
/* not enough memory for new pages */ |
|
err = -ENOMEM; |
|
goto out_err; |
|
} |
|
} |
|
|
|
get_online_cpus(); |
|
/* |
|
* Fire off all the required work handlers |
|
* We can't schedule on offline CPUs, but it's not necessary |
|
* since we can change their buffer sizes without any race. |
|
*/ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
if (!cpu_buffer->nr_pages_to_update) |
|
continue; |
|
|
|
/* Can't run something on an offline CPU. */ |
|
if (!cpu_online(cpu)) { |
|
rb_update_pages(cpu_buffer); |
|
cpu_buffer->nr_pages_to_update = 0; |
|
} else { |
|
schedule_work_on(cpu, |
|
&cpu_buffer->update_pages_work); |
|
} |
|
} |
|
|
|
/* wait for all the updates to complete */ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
if (!cpu_buffer->nr_pages_to_update) |
|
continue; |
|
|
|
if (cpu_online(cpu)) |
|
wait_for_completion(&cpu_buffer->update_done); |
|
cpu_buffer->nr_pages_to_update = 0; |
|
} |
|
|
|
put_online_cpus(); |
|
} else { |
|
cpu_buffer = buffer->buffers[cpu_id]; |
|
|
|
if (nr_pages == cpu_buffer->nr_pages) |
|
goto out; |
|
|
|
/* |
|
* Don't succeed if resizing is disabled, as a reader might be |
|
* manipulating the ring buffer and is expecting a sane state while |
|
* this is true. |
|
*/ |
|
if (atomic_read(&cpu_buffer->resize_disabled)) { |
|
err = -EBUSY; |
|
goto out_err_unlock; |
|
} |
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages - |
|
cpu_buffer->nr_pages; |
|
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages); |
|
if (cpu_buffer->nr_pages_to_update > 0 && |
|
__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update, |
|
&cpu_buffer->new_pages)) { |
|
err = -ENOMEM; |
|
goto out_err; |
|
} |
|
|
|
get_online_cpus(); |
|
|
|
/* Can't run something on an offline CPU. */ |
|
if (!cpu_online(cpu_id)) |
|
rb_update_pages(cpu_buffer); |
|
else { |
|
schedule_work_on(cpu_id, |
|
&cpu_buffer->update_pages_work); |
|
wait_for_completion(&cpu_buffer->update_done); |
|
} |
|
|
|
cpu_buffer->nr_pages_to_update = 0; |
|
put_online_cpus(); |
|
} |
|
|
|
out: |
|
/* |
|
* The ring buffer resize can happen with the ring buffer |
|
* enabled, so that the update disturbs the tracing as little |
|
* as possible. But if the buffer is disabled, we do not need |
|
* to worry about that, and we can take the time to verify |
|
* that the buffer is not corrupt. |
|
*/ |
|
if (atomic_read(&buffer->record_disabled)) { |
|
atomic_inc(&buffer->record_disabled); |
|
/* |
|
* Even though the buffer was disabled, we must make sure |
|
* that it is truly disabled before calling rb_check_pages. |
|
* There could have been a race between checking |
|
* record_disable and incrementing it. |
|
*/ |
|
synchronize_rcu(); |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
rb_check_pages(cpu_buffer); |
|
} |
|
atomic_dec(&buffer->record_disabled); |
|
} |
|
|
|
mutex_unlock(&buffer->mutex); |
|
return 0; |
|
|
|
out_err: |
|
for_each_buffer_cpu(buffer, cpu) { |
|
struct buffer_page *bpage, *tmp; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
cpu_buffer->nr_pages_to_update = 0; |
|
|
|
if (list_empty(&cpu_buffer->new_pages)) |
|
continue; |
|
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
|
list) { |
|
list_del_init(&bpage->list); |
|
free_buffer_page(bpage); |
|
} |
|
} |
|
out_err_unlock: |
|
mutex_unlock(&buffer->mutex); |
|
return err; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_resize); |
|
|
|
void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val) |
|
{ |
|
mutex_lock(&buffer->mutex); |
|
if (val) |
|
buffer->flags |= RB_FL_OVERWRITE; |
|
else |
|
buffer->flags &= ~RB_FL_OVERWRITE; |
|
mutex_unlock(&buffer->mutex); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); |
|
|
|
static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
|
{ |
|
return bpage->page->data + index; |
|
} |
|
|
|
static __always_inline struct ring_buffer_event * |
|
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
return __rb_page_index(cpu_buffer->reader_page, |
|
cpu_buffer->reader_page->read); |
|
} |
|
|
|
static __always_inline unsigned rb_page_commit(struct buffer_page *bpage) |
|
{ |
|
return local_read(&bpage->page->commit); |
|
} |
|
|
|
static struct ring_buffer_event * |
|
rb_iter_head_event(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct buffer_page *iter_head_page = iter->head_page; |
|
unsigned long commit; |
|
unsigned length; |
|
|
|
if (iter->head != iter->next_event) |
|
return iter->event; |
|
|
|
/* |
|
* When the writer goes across pages, it issues a cmpxchg which |
|
* is a mb(), which will synchronize with the rmb here. |
|
* (see rb_tail_page_update() and __rb_reserve_next()) |
|
*/ |
|
commit = rb_page_commit(iter_head_page); |
|
smp_rmb(); |
|
event = __rb_page_index(iter_head_page, iter->head); |
|
length = rb_event_length(event); |
|
|
|
/* |
|
* READ_ONCE() doesn't work on functions and we don't want the |
|
* compiler doing any crazy optimizations with length. |
|
*/ |
|
barrier(); |
|
|
|
if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE) |
|
/* Writer corrupted the read? */ |
|
goto reset; |
|
|
|
memcpy(iter->event, event, length); |
|
/* |
|
* If the page stamp is still the same after this rmb() then the |
|
* event was safely copied without the writer entering the page. |
|
*/ |
|
smp_rmb(); |
|
|
|
/* Make sure the page didn't change since we read this */ |
|
if (iter->page_stamp != iter_head_page->page->time_stamp || |
|
commit > rb_page_commit(iter_head_page)) |
|
goto reset; |
|
|
|
iter->next_event = iter->head + length; |
|
return iter->event; |
|
reset: |
|
/* Reset to the beginning */ |
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; |
|
iter->head = 0; |
|
iter->next_event = 0; |
|
iter->missed_events = 1; |
|
return NULL; |
|
} |
|
|
|
/* Size is determined by what has been committed */ |
|
static __always_inline unsigned rb_page_size(struct buffer_page *bpage) |
|
{ |
|
return rb_page_commit(bpage); |
|
} |
|
|
|
static __always_inline unsigned |
|
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
return rb_page_commit(cpu_buffer->commit_page); |
|
} |
|
|
|
static __always_inline unsigned |
|
rb_event_index(struct ring_buffer_event *event) |
|
{ |
|
unsigned long addr = (unsigned long)event; |
|
|
|
return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
|
} |
|
|
|
static void rb_inc_iter(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
|
|
|
/* |
|
* The iterator could be on the reader page (it starts there). |
|
* But the head could have moved, since the reader was |
|
* found. Check for this case and assign the iterator |
|
* to the head page instead of next. |
|
*/ |
|
if (iter->head_page == cpu_buffer->reader_page) |
|
iter->head_page = rb_set_head_page(cpu_buffer); |
|
else |
|
rb_inc_page(&iter->head_page); |
|
|
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; |
|
iter->head = 0; |
|
iter->next_event = 0; |
|
} |
|
|
|
/* |
|
* rb_handle_head_page - writer hit the head page |
|
* |
|
* Returns: +1 to retry page |
|
* 0 to continue |
|
* -1 on error |
|
*/ |
|
static int |
|
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct buffer_page *tail_page, |
|
struct buffer_page *next_page) |
|
{ |
|
struct buffer_page *new_head; |
|
int entries; |
|
int type; |
|
int ret; |
|
|
|
entries = rb_page_entries(next_page); |
|
|
|
/* |
|
* The hard part is here. We need to move the head |
|
* forward, and protect against both readers on |
|
* other CPUs and writers coming in via interrupts. |
|
*/ |
|
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, |
|
RB_PAGE_HEAD); |
|
|
|
/* |
|
* type can be one of four: |
|
* NORMAL - an interrupt already moved it for us |
|
* HEAD - we are the first to get here. |
|
* UPDATE - we are the interrupt interrupting |
|
* a current move. |
|
* MOVED - a reader on another CPU moved the next |
|
* pointer to its reader page. Give up |
|
* and try again. |
|
*/ |
|
|
|
switch (type) { |
|
case RB_PAGE_HEAD: |
|
/* |
|
* We changed the head to UPDATE, thus |
|
* it is our responsibility to update |
|
* the counters. |
|
*/ |
|
local_add(entries, &cpu_buffer->overrun); |
|
local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
|
|
|
/* |
|
* The entries will be zeroed out when we move the |
|
* tail page. |
|
*/ |
|
|
|
/* still more to do */ |
|
break; |
|
|
|
case RB_PAGE_UPDATE: |
|
/* |
|
* This is an interrupt that interrupt the |
|
* previous update. Still more to do. |
|
*/ |
|
break; |
|
case RB_PAGE_NORMAL: |
|
/* |
|
* An interrupt came in before the update |
|
* and processed this for us. |
|
* Nothing left to do. |
|
*/ |
|
return 1; |
|
case RB_PAGE_MOVED: |
|
/* |
|
* The reader is on another CPU and just did |
|
* a swap with our next_page. |
|
* Try again. |
|
*/ |
|
return 1; |
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ |
|
return -1; |
|
} |
|
|
|
/* |
|
* Now that we are here, the old head pointer is |
|
* set to UPDATE. This will keep the reader from |
|
* swapping the head page with the reader page. |
|
* The reader (on another CPU) will spin till |
|
* we are finished. |
|
* |
|
* We just need to protect against interrupts |
|
* doing the job. We will set the next pointer |
|
* to HEAD. After that, we set the old pointer |
|
* to NORMAL, but only if it was HEAD before. |
|
* otherwise we are an interrupt, and only |
|
* want the outer most commit to reset it. |
|
*/ |
|
new_head = next_page; |
|
rb_inc_page(&new_head); |
|
|
|
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, |
|
RB_PAGE_NORMAL); |
|
|
|
/* |
|
* Valid returns are: |
|
* HEAD - an interrupt came in and already set it. |
|
* NORMAL - One of two things: |
|
* 1) We really set it. |
|
* 2) A bunch of interrupts came in and moved |
|
* the page forward again. |
|
*/ |
|
switch (ret) { |
|
case RB_PAGE_HEAD: |
|
case RB_PAGE_NORMAL: |
|
/* OK */ |
|
break; |
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); |
|
return -1; |
|
} |
|
|
|
/* |
|
* It is possible that an interrupt came in, |
|
* set the head up, then more interrupts came in |
|
* and moved it again. When we get back here, |
|
* the page would have been set to NORMAL but we |
|
* just set it back to HEAD. |
|
* |
|
* How do you detect this? Well, if that happened |
|
* the tail page would have moved. |
|
*/ |
|
if (ret == RB_PAGE_NORMAL) { |
|
struct buffer_page *buffer_tail_page; |
|
|
|
buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); |
|
/* |
|
* If the tail had moved passed next, then we need |
|
* to reset the pointer. |
|
*/ |
|
if (buffer_tail_page != tail_page && |
|
buffer_tail_page != next_page) |
|
rb_head_page_set_normal(cpu_buffer, new_head, |
|
next_page, |
|
RB_PAGE_HEAD); |
|
} |
|
|
|
/* |
|
* If this was the outer most commit (the one that |
|
* changed the original pointer from HEAD to UPDATE), |
|
* then it is up to us to reset it to NORMAL. |
|
*/ |
|
if (type == RB_PAGE_HEAD) { |
|
ret = rb_head_page_set_normal(cpu_buffer, next_page, |
|
tail_page, |
|
RB_PAGE_UPDATE); |
|
if (RB_WARN_ON(cpu_buffer, |
|
ret != RB_PAGE_UPDATE)) |
|
return -1; |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static inline void |
|
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, |
|
unsigned long tail, struct rb_event_info *info) |
|
{ |
|
struct buffer_page *tail_page = info->tail_page; |
|
struct ring_buffer_event *event; |
|
unsigned long length = info->length; |
|
|
|
/* |
|
* Only the event that crossed the page boundary |
|
* must fill the old tail_page with padding. |
|
*/ |
|
if (tail >= BUF_PAGE_SIZE) { |
|
/* |
|
* If the page was filled, then we still need |
|
* to update the real_end. Reset it to zero |
|
* and the reader will ignore it. |
|
*/ |
|
if (tail == BUF_PAGE_SIZE) |
|
tail_page->real_end = 0; |
|
|
|
local_sub(length, &tail_page->write); |
|
return; |
|
} |
|
|
|
event = __rb_page_index(tail_page, tail); |
|
|
|
/* account for padding bytes */ |
|
local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); |
|
|
|
/* |
|
* Save the original length to the meta data. |
|
* This will be used by the reader to add lost event |
|
* counter. |
|
*/ |
|
tail_page->real_end = tail; |
|
|
|
/* |
|
* If this event is bigger than the minimum size, then |
|
* we need to be careful that we don't subtract the |
|
* write counter enough to allow another writer to slip |
|
* in on this page. |
|
* We put in a discarded commit instead, to make sure |
|
* that this space is not used again. |
|
* |
|
* If we are less than the minimum size, we don't need to |
|
* worry about it. |
|
*/ |
|
if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { |
|
/* No room for any events */ |
|
|
|
/* Mark the rest of the page with padding */ |
|
rb_event_set_padding(event); |
|
|
|
/* Set the write back to the previous setting */ |
|
local_sub(length, &tail_page->write); |
|
return; |
|
} |
|
|
|
/* Put in a discarded event */ |
|
event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; |
|
event->type_len = RINGBUF_TYPE_PADDING; |
|
/* time delta must be non zero */ |
|
event->time_delta = 1; |
|
|
|
/* Set write to end of buffer */ |
|
length = (tail + length) - BUF_PAGE_SIZE; |
|
local_sub(length, &tail_page->write); |
|
} |
|
|
|
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); |
|
|
|
/* |
|
* This is the slow path, force gcc not to inline it. |
|
*/ |
|
static noinline struct ring_buffer_event * |
|
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
|
unsigned long tail, struct rb_event_info *info) |
|
{ |
|
struct buffer_page *tail_page = info->tail_page; |
|
struct buffer_page *commit_page = cpu_buffer->commit_page; |
|
struct trace_buffer *buffer = cpu_buffer->buffer; |
|
struct buffer_page *next_page; |
|
int ret; |
|
|
|
next_page = tail_page; |
|
|
|
rb_inc_page(&next_page); |
|
|
|
/* |
|
* If for some reason, we had an interrupt storm that made |
|
* it all the way around the buffer, bail, and warn |
|
* about it. |
|
*/ |
|
if (unlikely(next_page == commit_page)) { |
|
local_inc(&cpu_buffer->commit_overrun); |
|
goto out_reset; |
|
} |
|
|
|
/* |
|
* This is where the fun begins! |
|
* |
|
* We are fighting against races between a reader that |
|
* could be on another CPU trying to swap its reader |
|
* page with the buffer head. |
|
* |
|
* We are also fighting against interrupts coming in and |
|
* moving the head or tail on us as well. |
|
* |
|
* If the next page is the head page then we have filled |
|
* the buffer, unless the commit page is still on the |
|
* reader page. |
|
*/ |
|
if (rb_is_head_page(next_page, &tail_page->list)) { |
|
|
|
/* |
|
* If the commit is not on the reader page, then |
|
* move the header page. |
|
*/ |
|
if (!rb_is_reader_page(cpu_buffer->commit_page)) { |
|
/* |
|
* If we are not in overwrite mode, |
|
* this is easy, just stop here. |
|
*/ |
|
if (!(buffer->flags & RB_FL_OVERWRITE)) { |
|
local_inc(&cpu_buffer->dropped_events); |
|
goto out_reset; |
|
} |
|
|
|
ret = rb_handle_head_page(cpu_buffer, |
|
tail_page, |
|
next_page); |
|
if (ret < 0) |
|
goto out_reset; |
|
if (ret) |
|
goto out_again; |
|
} else { |
|
/* |
|
* We need to be careful here too. The |
|
* commit page could still be on the reader |
|
* page. We could have a small buffer, and |
|
* have filled up the buffer with events |
|
* from interrupts and such, and wrapped. |
|
* |
|
* Note, if the tail page is also on the |
|
* reader_page, we let it move out. |
|
*/ |
|
if (unlikely((cpu_buffer->commit_page != |
|
cpu_buffer->tail_page) && |
|
(cpu_buffer->commit_page == |
|
cpu_buffer->reader_page))) { |
|
local_inc(&cpu_buffer->commit_overrun); |
|
goto out_reset; |
|
} |
|
} |
|
} |
|
|
|
rb_tail_page_update(cpu_buffer, tail_page, next_page); |
|
|
|
out_again: |
|
|
|
rb_reset_tail(cpu_buffer, tail, info); |
|
|
|
/* Commit what we have for now. */ |
|
rb_end_commit(cpu_buffer); |
|
/* rb_end_commit() decs committing */ |
|
local_inc(&cpu_buffer->committing); |
|
|
|
/* fail and let the caller try again */ |
|
return ERR_PTR(-EAGAIN); |
|
|
|
out_reset: |
|
/* reset write */ |
|
rb_reset_tail(cpu_buffer, tail, info); |
|
|
|
return NULL; |
|
} |
|
|
|
/* Slow path */ |
|
static struct ring_buffer_event * |
|
rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) |
|
{ |
|
if (abs) |
|
event->type_len = RINGBUF_TYPE_TIME_STAMP; |
|
else |
|
event->type_len = RINGBUF_TYPE_TIME_EXTEND; |
|
|
|
/* Not the first event on the page, or not delta? */ |
|
if (abs || rb_event_index(event)) { |
|
event->time_delta = delta & TS_MASK; |
|
event->array[0] = delta >> TS_SHIFT; |
|
} else { |
|
/* nope, just zero it */ |
|
event->time_delta = 0; |
|
event->array[0] = 0; |
|
} |
|
|
|
return skip_time_extend(event); |
|
} |
|
|
|
#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
|
static inline bool sched_clock_stable(void) |
|
{ |
|
return true; |
|
} |
|
#endif |
|
|
|
static void |
|
rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct rb_event_info *info) |
|
{ |
|
u64 write_stamp; |
|
|
|
WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s", |
|
(unsigned long long)info->delta, |
|
(unsigned long long)info->ts, |
|
(unsigned long long)info->before, |
|
(unsigned long long)info->after, |
|
(unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0), |
|
sched_clock_stable() ? "" : |
|
"If you just came from a suspend/resume,\n" |
|
"please switch to the trace global clock:\n" |
|
" echo global > /sys/kernel/debug/tracing/trace_clock\n" |
|
"or add trace_clock=global to the kernel command line\n"); |
|
} |
|
|
|
static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event **event, |
|
struct rb_event_info *info, |
|
u64 *delta, |
|
unsigned int *length) |
|
{ |
|
bool abs = info->add_timestamp & |
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE); |
|
|
|
if (unlikely(info->delta > (1ULL << 59))) { |
|
/* did the clock go backwards */ |
|
if (info->before == info->after && info->before > info->ts) { |
|
/* not interrupted */ |
|
static int once; |
|
|
|
/* |
|
* This is possible with a recalibrating of the TSC. |
|
* Do not produce a call stack, but just report it. |
|
*/ |
|
if (!once) { |
|
once++; |
|
pr_warn("Ring buffer clock went backwards: %llu -> %llu\n", |
|
info->before, info->ts); |
|
} |
|
} else |
|
rb_check_timestamp(cpu_buffer, info); |
|
if (!abs) |
|
info->delta = 0; |
|
} |
|
*event = rb_add_time_stamp(*event, info->delta, abs); |
|
*length -= RB_LEN_TIME_EXTEND; |
|
*delta = 0; |
|
} |
|
|
|
/** |
|
* rb_update_event - update event type and data |
|
* @cpu_buffer: The per cpu buffer of the @event |
|
* @event: the event to update |
|
* @info: The info to update the @event with (contains length and delta) |
|
* |
|
* Update the type and data fields of the @event. The length |
|
* is the actual size that is written to the ring buffer, |
|
* and with this, we can determine what to place into the |
|
* data field. |
|
*/ |
|
static void |
|
rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event *event, |
|
struct rb_event_info *info) |
|
{ |
|
unsigned length = info->length; |
|
u64 delta = info->delta; |
|
|
|
/* |
|
* If we need to add a timestamp, then we |
|
* add it to the start of the reserved space. |
|
*/ |
|
if (unlikely(info->add_timestamp)) |
|
rb_add_timestamp(cpu_buffer, &event, info, &delta, &length); |
|
|
|
event->time_delta = delta; |
|
length -= RB_EVNT_HDR_SIZE; |
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { |
|
event->type_len = 0; |
|
event->array[0] = length; |
|
} else |
|
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); |
|
} |
|
|
|
static unsigned rb_calculate_event_length(unsigned length) |
|
{ |
|
struct ring_buffer_event event; /* Used only for sizeof array */ |
|
|
|
/* zero length can cause confusions */ |
|
if (!length) |
|
length++; |
|
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
|
length += sizeof(event.array[0]); |
|
|
|
length += RB_EVNT_HDR_SIZE; |
|
length = ALIGN(length, RB_ARCH_ALIGNMENT); |
|
|
|
/* |
|
* In case the time delta is larger than the 27 bits for it |
|
* in the header, we need to add a timestamp. If another |
|
* event comes in when trying to discard this one to increase |
|
* the length, then the timestamp will be added in the allocated |
|
* space of this event. If length is bigger than the size needed |
|
* for the TIME_EXTEND, then padding has to be used. The events |
|
* length must be either RB_LEN_TIME_EXTEND, or greater than or equal |
|
* to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. |
|
* As length is a multiple of 4, we only need to worry if it |
|
* is 12 (RB_LEN_TIME_EXTEND + 4). |
|
*/ |
|
if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) |
|
length += RB_ALIGNMENT; |
|
|
|
return length; |
|
} |
|
|
|
static u64 rb_time_delta(struct ring_buffer_event *event) |
|
{ |
|
switch (event->type_len) { |
|
case RINGBUF_TYPE_PADDING: |
|
return 0; |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
return ring_buffer_event_time_stamp(event); |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
return 0; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
return event->time_delta; |
|
default: |
|
return 0; |
|
} |
|
} |
|
|
|
static inline int |
|
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
unsigned long new_index, old_index; |
|
struct buffer_page *bpage; |
|
unsigned long index; |
|
unsigned long addr; |
|
u64 write_stamp; |
|
u64 delta; |
|
|
|
new_index = rb_event_index(event); |
|
old_index = new_index + rb_event_ts_length(event); |
|
addr = (unsigned long)event; |
|
addr &= PAGE_MASK; |
|
|
|
bpage = READ_ONCE(cpu_buffer->tail_page); |
|
|
|
delta = rb_time_delta(event); |
|
|
|
if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp)) |
|
return 0; |
|
|
|
/* Make sure the write stamp is read before testing the location */ |
|
barrier(); |
|
|
|
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { |
|
unsigned long write_mask = |
|
local_read(&bpage->write) & ~RB_WRITE_MASK; |
|
unsigned long event_length = rb_event_length(event); |
|
|
|
/* Something came in, can't discard */ |
|
if (!rb_time_cmpxchg(&cpu_buffer->write_stamp, |
|
write_stamp, write_stamp - delta)) |
|
return 0; |
|
|
|
/* |
|
* It's possible that the event time delta is zero |
|
* (has the same time stamp as the previous event) |
|
* in which case write_stamp and before_stamp could |
|
* be the same. In such a case, force before_stamp |
|
* to be different than write_stamp. It doesn't |
|
* matter what it is, as long as its different. |
|
*/ |
|
if (!delta) |
|
rb_time_set(&cpu_buffer->before_stamp, 0); |
|
|
|
/* |
|
* If an event were to come in now, it would see that the |
|
* write_stamp and the before_stamp are different, and assume |
|
* that this event just added itself before updating |
|
* the write stamp. The interrupting event will fix the |
|
* write stamp for us, and use the before stamp as its delta. |
|
*/ |
|
|
|
/* |
|
* This is on the tail page. It is possible that |
|
* a write could come in and move the tail page |
|
* and write to the next page. That is fine |
|
* because we just shorten what is on this page. |
|
*/ |
|
old_index += write_mask; |
|
new_index += write_mask; |
|
index = local_cmpxchg(&bpage->write, old_index, new_index); |
|
if (index == old_index) { |
|
/* update counters */ |
|
local_sub(event_length, &cpu_buffer->entries_bytes); |
|
return 1; |
|
} |
|
} |
|
|
|
/* could not discard */ |
|
return 0; |
|
} |
|
|
|
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
local_inc(&cpu_buffer->committing); |
|
local_inc(&cpu_buffer->commits); |
|
} |
|
|
|
static __always_inline void |
|
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
unsigned long max_count; |
|
|
|
/* |
|
* We only race with interrupts and NMIs on this CPU. |
|
* If we own the commit event, then we can commit |
|
* all others that interrupted us, since the interruptions |
|
* are in stack format (they finish before they come |
|
* back to us). This allows us to do a simple loop to |
|
* assign the commit to the tail. |
|
*/ |
|
again: |
|
max_count = cpu_buffer->nr_pages * 100; |
|
|
|
while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { |
|
if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
|
return; |
|
if (RB_WARN_ON(cpu_buffer, |
|
rb_is_reader_page(cpu_buffer->tail_page))) |
|
return; |
|
local_set(&cpu_buffer->commit_page->page->commit, |
|
rb_page_write(cpu_buffer->commit_page)); |
|
rb_inc_page(&cpu_buffer->commit_page); |
|
/* add barrier to keep gcc from optimizing too much */ |
|
barrier(); |
|
} |
|
while (rb_commit_index(cpu_buffer) != |
|
rb_page_write(cpu_buffer->commit_page)) { |
|
|
|
local_set(&cpu_buffer->commit_page->page->commit, |
|
rb_page_write(cpu_buffer->commit_page)); |
|
RB_WARN_ON(cpu_buffer, |
|
local_read(&cpu_buffer->commit_page->page->commit) & |
|
~RB_WRITE_MASK); |
|
barrier(); |
|
} |
|
|
|
/* again, keep gcc from optimizing */ |
|
barrier(); |
|
|
|
/* |
|
* If an interrupt came in just after the first while loop |
|
* and pushed the tail page forward, we will be left with |
|
* a dangling commit that will never go forward. |
|
*/ |
|
if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) |
|
goto again; |
|
} |
|
|
|
static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
unsigned long commits; |
|
|
|
if (RB_WARN_ON(cpu_buffer, |
|
!local_read(&cpu_buffer->committing))) |
|
return; |
|
|
|
again: |
|
commits = local_read(&cpu_buffer->commits); |
|
/* synchronize with interrupts */ |
|
barrier(); |
|
if (local_read(&cpu_buffer->committing) == 1) |
|
rb_set_commit_to_write(cpu_buffer); |
|
|
|
local_dec(&cpu_buffer->committing); |
|
|
|
/* synchronize with interrupts */ |
|
barrier(); |
|
|
|
/* |
|
* Need to account for interrupts coming in between the |
|
* updating of the commit page and the clearing of the |
|
* committing counter. |
|
*/ |
|
if (unlikely(local_read(&cpu_buffer->commits) != commits) && |
|
!local_read(&cpu_buffer->committing)) { |
|
local_inc(&cpu_buffer->committing); |
|
goto again; |
|
} |
|
} |
|
|
|
static inline void rb_event_discard(struct ring_buffer_event *event) |
|
{ |
|
if (extended_time(event)) |
|
event = skip_time_extend(event); |
|
|
|
/* array[0] holds the actual length for the discarded event */ |
|
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; |
|
event->type_len = RINGBUF_TYPE_PADDING; |
|
/* time delta must be non zero */ |
|
if (!event->time_delta) |
|
event->time_delta = 1; |
|
} |
|
|
|
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
local_inc(&cpu_buffer->entries); |
|
rb_end_commit(cpu_buffer); |
|
} |
|
|
|
static __always_inline void |
|
rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
size_t nr_pages; |
|
size_t dirty; |
|
size_t full; |
|
|
|
if (buffer->irq_work.waiters_pending) { |
|
buffer->irq_work.waiters_pending = false; |
|
/* irq_work_queue() supplies it's own memory barriers */ |
|
irq_work_queue(&buffer->irq_work.work); |
|
} |
|
|
|
if (cpu_buffer->irq_work.waiters_pending) { |
|
cpu_buffer->irq_work.waiters_pending = false; |
|
/* irq_work_queue() supplies it's own memory barriers */ |
|
irq_work_queue(&cpu_buffer->irq_work.work); |
|
} |
|
|
|
if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) |
|
return; |
|
|
|
if (cpu_buffer->reader_page == cpu_buffer->commit_page) |
|
return; |
|
|
|
if (!cpu_buffer->irq_work.full_waiters_pending) |
|
return; |
|
|
|
cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); |
|
|
|
full = cpu_buffer->shortest_full; |
|
nr_pages = cpu_buffer->nr_pages; |
|
dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu); |
|
if (full && nr_pages && (dirty * 100) <= full * nr_pages) |
|
return; |
|
|
|
cpu_buffer->irq_work.wakeup_full = true; |
|
cpu_buffer->irq_work.full_waiters_pending = false; |
|
/* irq_work_queue() supplies it's own memory barriers */ |
|
irq_work_queue(&cpu_buffer->irq_work.work); |
|
} |
|
|
|
#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION |
|
# define do_ring_buffer_record_recursion() \ |
|
do_ftrace_record_recursion(_THIS_IP_, _RET_IP_) |
|
#else |
|
# define do_ring_buffer_record_recursion() do { } while (0) |
|
#endif |
|
|
|
/* |
|
* The lock and unlock are done within a preempt disable section. |
|
* The current_context per_cpu variable can only be modified |
|
* by the current task between lock and unlock. But it can |
|
* be modified more than once via an interrupt. To pass this |
|
* information from the lock to the unlock without having to |
|
* access the 'in_interrupt()' functions again (which do show |
|
* a bit of overhead in something as critical as function tracing, |
|
* we use a bitmask trick. |
|
* |
|
* bit 1 = NMI context |
|
* bit 2 = IRQ context |
|
* bit 3 = SoftIRQ context |
|
* bit 4 = normal context. |
|
* |
|
* This works because this is the order of contexts that can |
|
* preempt other contexts. A SoftIRQ never preempts an IRQ |
|
* context. |
|
* |
|
* When the context is determined, the corresponding bit is |
|
* checked and set (if it was set, then a recursion of that context |
|
* happened). |
|
* |
|
* On unlock, we need to clear this bit. To do so, just subtract |
|
* 1 from the current_context and AND it to itself. |
|
* |
|
* (binary) |
|
* 101 - 1 = 100 |
|
* 101 & 100 = 100 (clearing bit zero) |
|
* |
|
* 1010 - 1 = 1001 |
|
* 1010 & 1001 = 1000 (clearing bit 1) |
|
* |
|
* The least significant bit can be cleared this way, and it |
|
* just so happens that it is the same bit corresponding to |
|
* the current context. |
|
* |
|
* Now the TRANSITION bit breaks the above slightly. The TRANSITION bit |
|
* is set when a recursion is detected at the current context, and if |
|
* the TRANSITION bit is already set, it will fail the recursion. |
|
* This is needed because there's a lag between the changing of |
|
* interrupt context and updating the preempt count. In this case, |
|
* a false positive will be found. To handle this, one extra recursion |
|
* is allowed, and this is done by the TRANSITION bit. If the TRANSITION |
|
* bit is already set, then it is considered a recursion and the function |
|
* ends. Otherwise, the TRANSITION bit is set, and that bit is returned. |
|
* |
|
* On the trace_recursive_unlock(), the TRANSITION bit will be the first |
|
* to be cleared. Even if it wasn't the context that set it. That is, |
|
* if an interrupt comes in while NORMAL bit is set and the ring buffer |
|
* is called before preempt_count() is updated, since the check will |
|
* be on the NORMAL bit, the TRANSITION bit will then be set. If an |
|
* NMI then comes in, it will set the NMI bit, but when the NMI code |
|
* does the trace_recursive_unlock() it will clear the TRANSTION bit |
|
* and leave the NMI bit set. But this is fine, because the interrupt |
|
* code that set the TRANSITION bit will then clear the NMI bit when it |
|
* calls trace_recursive_unlock(). If another NMI comes in, it will |
|
* set the TRANSITION bit and continue. |
|
* |
|
* Note: The TRANSITION bit only handles a single transition between context. |
|
*/ |
|
|
|
static __always_inline int |
|
trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
unsigned int val = cpu_buffer->current_context; |
|
unsigned long pc = preempt_count(); |
|
int bit; |
|
|
|
if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
|
bit = RB_CTX_NORMAL; |
|
else |
|
bit = pc & NMI_MASK ? RB_CTX_NMI : |
|
pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ; |
|
|
|
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) { |
|
/* |
|
* It is possible that this was called by transitioning |
|
* between interrupt context, and preempt_count() has not |
|
* been updated yet. In this case, use the TRANSITION bit. |
|
*/ |
|
bit = RB_CTX_TRANSITION; |
|
if (val & (1 << (bit + cpu_buffer->nest))) { |
|
do_ring_buffer_record_recursion(); |
|
return 1; |
|
} |
|
} |
|
|
|
val |= (1 << (bit + cpu_buffer->nest)); |
|
cpu_buffer->current_context = val; |
|
|
|
return 0; |
|
} |
|
|
|
static __always_inline void |
|
trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
cpu_buffer->current_context &= |
|
cpu_buffer->current_context - (1 << cpu_buffer->nest); |
|
} |
|
|
|
/* The recursive locking above uses 5 bits */ |
|
#define NESTED_BITS 5 |
|
|
|
/** |
|
* ring_buffer_nest_start - Allow to trace while nested |
|
* @buffer: The ring buffer to modify |
|
* |
|
* The ring buffer has a safety mechanism to prevent recursion. |
|
* But there may be a case where a trace needs to be done while |
|
* tracing something else. In this case, calling this function |
|
* will allow this function to nest within a currently active |
|
* ring_buffer_lock_reserve(). |
|
* |
|
* Call this function before calling another ring_buffer_lock_reserve() and |
|
* call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). |
|
*/ |
|
void ring_buffer_nest_start(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu; |
|
|
|
/* Enabled by ring_buffer_nest_end() */ |
|
preempt_disable_notrace(); |
|
cpu = raw_smp_processor_id(); |
|
cpu_buffer = buffer->buffers[cpu]; |
|
/* This is the shift value for the above recursive locking */ |
|
cpu_buffer->nest += NESTED_BITS; |
|
} |
|
|
|
/** |
|
* ring_buffer_nest_end - Allow to trace while nested |
|
* @buffer: The ring buffer to modify |
|
* |
|
* Must be called after ring_buffer_nest_start() and after the |
|
* ring_buffer_unlock_commit(). |
|
*/ |
|
void ring_buffer_nest_end(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu; |
|
|
|
/* disabled by ring_buffer_nest_start() */ |
|
cpu = raw_smp_processor_id(); |
|
cpu_buffer = buffer->buffers[cpu]; |
|
/* This is the shift value for the above recursive locking */ |
|
cpu_buffer->nest -= NESTED_BITS; |
|
preempt_enable_notrace(); |
|
} |
|
|
|
/** |
|
* ring_buffer_unlock_commit - commit a reserved |
|
* @buffer: The buffer to commit to |
|
* @event: The event pointer to commit. |
|
* |
|
* This commits the data to the ring buffer, and releases any locks held. |
|
* |
|
* Must be paired with ring_buffer_lock_reserve. |
|
*/ |
|
int ring_buffer_unlock_commit(struct trace_buffer *buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu = raw_smp_processor_id(); |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
rb_commit(cpu_buffer, event); |
|
|
|
rb_wakeups(buffer, cpu_buffer); |
|
|
|
trace_recursive_unlock(cpu_buffer); |
|
|
|
preempt_enable_notrace(); |
|
|
|
return 0; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
|
|
|
/* Special value to validate all deltas on a page. */ |
|
#define CHECK_FULL_PAGE 1L |
|
|
|
#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS |
|
static void dump_buffer_page(struct buffer_data_page *bpage, |
|
struct rb_event_info *info, |
|
unsigned long tail) |
|
{ |
|
struct ring_buffer_event *event; |
|
u64 ts, delta; |
|
int e; |
|
|
|
ts = bpage->time_stamp; |
|
pr_warn(" [%lld] PAGE TIME STAMP\n", ts); |
|
|
|
for (e = 0; e < tail; e += rb_event_length(event)) { |
|
|
|
event = (struct ring_buffer_event *)(bpage->data + e); |
|
|
|
switch (event->type_len) { |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
delta = ring_buffer_event_time_stamp(event); |
|
ts += delta; |
|
pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta); |
|
break; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
delta = ring_buffer_event_time_stamp(event); |
|
ts = delta; |
|
pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta); |
|
break; |
|
|
|
case RINGBUF_TYPE_PADDING: |
|
ts += event->time_delta; |
|
pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta); |
|
break; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
ts += event->time_delta; |
|
pr_warn(" [%lld] delta:%d\n", ts, event->time_delta); |
|
break; |
|
|
|
default: |
|
break; |
|
} |
|
} |
|
} |
|
|
|
static DEFINE_PER_CPU(atomic_t, checking); |
|
static atomic_t ts_dump; |
|
|
|
/* |
|
* Check if the current event time stamp matches the deltas on |
|
* the buffer page. |
|
*/ |
|
static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct rb_event_info *info, |
|
unsigned long tail) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct buffer_data_page *bpage; |
|
u64 ts, delta; |
|
bool full = false; |
|
int e; |
|
|
|
bpage = info->tail_page->page; |
|
|
|
if (tail == CHECK_FULL_PAGE) { |
|
full = true; |
|
tail = local_read(&bpage->commit); |
|
} else if (info->add_timestamp & |
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) { |
|
/* Ignore events with absolute time stamps */ |
|
return; |
|
} |
|
|
|
/* |
|
* Do not check the first event (skip possible extends too). |
|
* Also do not check if previous events have not been committed. |
|
*/ |
|
if (tail <= 8 || tail > local_read(&bpage->commit)) |
|
return; |
|
|
|
/* |
|
* If this interrupted another event, |
|
*/ |
|
if (atomic_inc_return(this_cpu_ptr(&checking)) != 1) |
|
goto out; |
|
|
|
ts = bpage->time_stamp; |
|
|
|
for (e = 0; e < tail; e += rb_event_length(event)) { |
|
|
|
event = (struct ring_buffer_event *)(bpage->data + e); |
|
|
|
switch (event->type_len) { |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
delta = ring_buffer_event_time_stamp(event); |
|
ts += delta; |
|
break; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
delta = ring_buffer_event_time_stamp(event); |
|
ts = delta; |
|
break; |
|
|
|
case RINGBUF_TYPE_PADDING: |
|
if (event->time_delta == 1) |
|
break; |
|
/* fall through */ |
|
case RINGBUF_TYPE_DATA: |
|
ts += event->time_delta; |
|
break; |
|
|
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); |
|
} |
|
} |
|
if ((full && ts > info->ts) || |
|
(!full && ts + info->delta != info->ts)) { |
|
/* If another report is happening, ignore this one */ |
|
if (atomic_inc_return(&ts_dump) != 1) { |
|
atomic_dec(&ts_dump); |
|
goto out; |
|
} |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
/* There's some cases in boot up that this can happen */ |
|
WARN_ON_ONCE(system_state != SYSTEM_BOOTING); |
|
pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n", |
|
cpu_buffer->cpu, |
|
ts + info->delta, info->ts, info->delta, |
|
info->before, info->after, |
|
full ? " (full)" : ""); |
|
dump_buffer_page(bpage, info, tail); |
|
atomic_dec(&ts_dump); |
|
/* Do not re-enable checking */ |
|
return; |
|
} |
|
out: |
|
atomic_dec(this_cpu_ptr(&checking)); |
|
} |
|
#else |
|
static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct rb_event_info *info, |
|
unsigned long tail) |
|
{ |
|
} |
|
#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */ |
|
|
|
static struct ring_buffer_event * |
|
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct rb_event_info *info) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct buffer_page *tail_page; |
|
unsigned long tail, write, w; |
|
bool a_ok; |
|
bool b_ok; |
|
|
|
/* Don't let the compiler play games with cpu_buffer->tail_page */ |
|
tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); |
|
|
|
/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK; |
|
barrier(); |
|
b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); |
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
|
barrier(); |
|
info->ts = rb_time_stamp(cpu_buffer->buffer); |
|
|
|
if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) { |
|
info->delta = info->ts; |
|
} else { |
|
/* |
|
* If interrupting an event time update, we may need an |
|
* absolute timestamp. |
|
* Don't bother if this is the start of a new page (w == 0). |
|
*/ |
|
if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) { |
|
info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND; |
|
info->length += RB_LEN_TIME_EXTEND; |
|
} else { |
|
info->delta = info->ts - info->after; |
|
if (unlikely(test_time_stamp(info->delta))) { |
|
info->add_timestamp |= RB_ADD_STAMP_EXTEND; |
|
info->length += RB_LEN_TIME_EXTEND; |
|
} |
|
} |
|
} |
|
|
|
/*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts); |
|
|
|
/*C*/ write = local_add_return(info->length, &tail_page->write); |
|
|
|
/* set write to only the index of the write */ |
|
write &= RB_WRITE_MASK; |
|
|
|
tail = write - info->length; |
|
|
|
/* See if we shot pass the end of this buffer page */ |
|
if (unlikely(write > BUF_PAGE_SIZE)) { |
|
/* before and after may now different, fix it up*/ |
|
b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); |
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
|
if (a_ok && b_ok && info->before != info->after) |
|
(void)rb_time_cmpxchg(&cpu_buffer->before_stamp, |
|
info->before, info->after); |
|
if (a_ok && b_ok) |
|
check_buffer(cpu_buffer, info, CHECK_FULL_PAGE); |
|
return rb_move_tail(cpu_buffer, tail, info); |
|
} |
|
|
|
if (likely(tail == w)) { |
|
u64 save_before; |
|
bool s_ok; |
|
|
|
/* Nothing interrupted us between A and C */ |
|
/*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts); |
|
barrier(); |
|
/*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before); |
|
RB_WARN_ON(cpu_buffer, !s_ok); |
|
if (likely(!(info->add_timestamp & |
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) |
|
/* This did not interrupt any time update */ |
|
info->delta = info->ts - info->after; |
|
else |
|
/* Just use full timestamp for interrupting event */ |
|
info->delta = info->ts; |
|
barrier(); |
|
check_buffer(cpu_buffer, info, tail); |
|
if (unlikely(info->ts != save_before)) { |
|
/* SLOW PATH - Interrupted between C and E */ |
|
|
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
|
RB_WARN_ON(cpu_buffer, !a_ok); |
|
|
|
/* Write stamp must only go forward */ |
|
if (save_before > info->after) { |
|
/* |
|
* We do not care about the result, only that |
|
* it gets updated atomically. |
|
*/ |
|
(void)rb_time_cmpxchg(&cpu_buffer->write_stamp, |
|
info->after, save_before); |
|
} |
|
} |
|
} else { |
|
u64 ts; |
|
/* SLOW PATH - Interrupted between A and C */ |
|
a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
|
/* Was interrupted before here, write_stamp must be valid */ |
|
RB_WARN_ON(cpu_buffer, !a_ok); |
|
ts = rb_time_stamp(cpu_buffer->buffer); |
|
barrier(); |
|
/*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && |
|
info->after < ts && |
|
rb_time_cmpxchg(&cpu_buffer->write_stamp, |
|
info->after, ts)) { |
|
/* Nothing came after this event between C and E */ |
|
info->delta = ts - info->after; |
|
info->ts = ts; |
|
} else { |
|
/* |
|
* Interrupted between C and E: |
|
* Lost the previous events time stamp. Just set the |
|
* delta to zero, and this will be the same time as |
|
* the event this event interrupted. And the events that |
|
* came after this will still be correct (as they would |
|
* have built their delta on the previous event. |
|
*/ |
|
info->delta = 0; |
|
} |
|
info->add_timestamp &= ~RB_ADD_STAMP_FORCE; |
|
} |
|
|
|
/* |
|
* If this is the first commit on the page, then it has the same |
|
* timestamp as the page itself. |
|
*/ |
|
if (unlikely(!tail && !(info->add_timestamp & |
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) |
|
info->delta = 0; |
|
|
|
/* We reserved something on the buffer */ |
|
|
|
event = __rb_page_index(tail_page, tail); |
|
rb_update_event(cpu_buffer, event, info); |
|
|
|
local_inc(&tail_page->entries); |
|
|
|
/* |
|
* If this is the first commit on the page, then update |
|
* its timestamp. |
|
*/ |
|
if (unlikely(!tail)) |
|
tail_page->page->time_stamp = info->ts; |
|
|
|
/* account for these added bytes */ |
|
local_add(info->length, &cpu_buffer->entries_bytes); |
|
|
|
return event; |
|
} |
|
|
|
static __always_inline struct ring_buffer_event * |
|
rb_reserve_next_event(struct trace_buffer *buffer, |
|
struct ring_buffer_per_cpu *cpu_buffer, |
|
unsigned long length) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct rb_event_info info; |
|
int nr_loops = 0; |
|
int add_ts_default; |
|
|
|
rb_start_commit(cpu_buffer); |
|
/* The commit page can not change after this */ |
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
|
/* |
|
* Due to the ability to swap a cpu buffer from a buffer |
|
* it is possible it was swapped before we committed. |
|
* (committing stops a swap). We check for it here and |
|
* if it happened, we have to fail the write. |
|
*/ |
|
barrier(); |
|
if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { |
|
local_dec(&cpu_buffer->committing); |
|
local_dec(&cpu_buffer->commits); |
|
return NULL; |
|
} |
|
#endif |
|
|
|
info.length = rb_calculate_event_length(length); |
|
|
|
if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) { |
|
add_ts_default = RB_ADD_STAMP_ABSOLUTE; |
|
info.length += RB_LEN_TIME_EXTEND; |
|
} else { |
|
add_ts_default = RB_ADD_STAMP_NONE; |
|
} |
|
|
|
again: |
|
info.add_timestamp = add_ts_default; |
|
info.delta = 0; |
|
|
|
/* |
|
* We allow for interrupts to reenter here and do a trace. |
|
* If one does, it will cause this original code to loop |
|
* back here. Even with heavy interrupts happening, this |
|
* should only happen a few times in a row. If this happens |
|
* 1000 times in a row, there must be either an interrupt |
|
* storm or we have something buggy. |
|
* Bail! |
|
*/ |
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
|
goto out_fail; |
|
|
|
event = __rb_reserve_next(cpu_buffer, &info); |
|
|
|
if (unlikely(PTR_ERR(event) == -EAGAIN)) { |
|
if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND)) |
|
info.length -= RB_LEN_TIME_EXTEND; |
|
goto again; |
|
} |
|
|
|
if (likely(event)) |
|
return event; |
|
out_fail: |
|
rb_end_commit(cpu_buffer); |
|
return NULL; |
|
} |
|
|
|
/** |
|
* ring_buffer_lock_reserve - reserve a part of the buffer |
|
* @buffer: the ring buffer to reserve from |
|
* @length: the length of the data to reserve (excluding event header) |
|
* |
|
* Returns a reserved event on the ring buffer to copy directly to. |
|
* The user of this interface will need to get the body to write into |
|
* and can use the ring_buffer_event_data() interface. |
|
* |
|
* The length is the length of the data needed, not the event length |
|
* which also includes the event header. |
|
* |
|
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned. |
|
* If NULL is returned, then nothing has been allocated or locked. |
|
*/ |
|
struct ring_buffer_event * |
|
ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct ring_buffer_event *event; |
|
int cpu; |
|
|
|
/* If we are tracing schedule, we don't want to recurse */ |
|
preempt_disable_notrace(); |
|
|
|
if (unlikely(atomic_read(&buffer->record_disabled))) |
|
goto out; |
|
|
|
cpu = raw_smp_processor_id(); |
|
|
|
if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
|
goto out; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
|
goto out; |
|
|
|
if (unlikely(length > BUF_MAX_DATA_SIZE)) |
|
goto out; |
|
|
|
if (unlikely(trace_recursive_lock(cpu_buffer))) |
|
goto out; |
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length); |
|
if (!event) |
|
goto out_unlock; |
|
|
|
return event; |
|
|
|
out_unlock: |
|
trace_recursive_unlock(cpu_buffer); |
|
out: |
|
preempt_enable_notrace(); |
|
return NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
|
|
|
/* |
|
* Decrement the entries to the page that an event is on. |
|
* The event does not even need to exist, only the pointer |
|
* to the page it is on. This may only be called before the commit |
|
* takes place. |
|
*/ |
|
static inline void |
|
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
unsigned long addr = (unsigned long)event; |
|
struct buffer_page *bpage = cpu_buffer->commit_page; |
|
struct buffer_page *start; |
|
|
|
addr &= PAGE_MASK; |
|
|
|
/* Do the likely case first */ |
|
if (likely(bpage->page == (void *)addr)) { |
|
local_dec(&bpage->entries); |
|
return; |
|
} |
|
|
|
/* |
|
* Because the commit page may be on the reader page we |
|
* start with the next page and check the end loop there. |
|
*/ |
|
rb_inc_page(&bpage); |
|
start = bpage; |
|
do { |
|
if (bpage->page == (void *)addr) { |
|
local_dec(&bpage->entries); |
|
return; |
|
} |
|
rb_inc_page(&bpage); |
|
} while (bpage != start); |
|
|
|
/* commit not part of this buffer?? */ |
|
RB_WARN_ON(cpu_buffer, 1); |
|
} |
|
|
|
/** |
|
* ring_buffer_discard_commit - discard an event that has not been committed |
|
* @buffer: the ring buffer |
|
* @event: non committed event to discard |
|
* |
|
* Sometimes an event that is in the ring buffer needs to be ignored. |
|
* This function lets the user discard an event in the ring buffer |
|
* and then that event will not be read later. |
|
* |
|
* This function only works if it is called before the item has been |
|
* committed. It will try to free the event from the ring buffer |
|
* if another event has not been added behind it. |
|
* |
|
* If another event has been added behind it, it will set the event |
|
* up as discarded, and perform the commit. |
|
* |
|
* If this function is called, do not call ring_buffer_unlock_commit on |
|
* the event. |
|
*/ |
|
void ring_buffer_discard_commit(struct trace_buffer *buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu; |
|
|
|
/* The event is discarded regardless */ |
|
rb_event_discard(event); |
|
|
|
cpu = smp_processor_id(); |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
/* |
|
* This must only be called if the event has not been |
|
* committed yet. Thus we can assume that preemption |
|
* is still disabled. |
|
*/ |
|
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
|
|
|
rb_decrement_entry(cpu_buffer, event); |
|
if (rb_try_to_discard(cpu_buffer, event)) |
|
goto out; |
|
|
|
out: |
|
rb_end_commit(cpu_buffer); |
|
|
|
trace_recursive_unlock(cpu_buffer); |
|
|
|
preempt_enable_notrace(); |
|
|
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); |
|
|
|
/** |
|
* ring_buffer_write - write data to the buffer without reserving |
|
* @buffer: The ring buffer to write to. |
|
* @length: The length of the data being written (excluding the event header) |
|
* @data: The data to write to the buffer. |
|
* |
|
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as |
|
* one function. If you already have the data to write to the buffer, it |
|
* may be easier to simply call this function. |
|
* |
|
* Note, like ring_buffer_lock_reserve, the length is the length of the data |
|
* and not the length of the event which would hold the header. |
|
*/ |
|
int ring_buffer_write(struct trace_buffer *buffer, |
|
unsigned long length, |
|
void *data) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct ring_buffer_event *event; |
|
void *body; |
|
int ret = -EBUSY; |
|
int cpu; |
|
|
|
preempt_disable_notrace(); |
|
|
|
if (atomic_read(&buffer->record_disabled)) |
|
goto out; |
|
|
|
cpu = raw_smp_processor_id(); |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
goto out; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
if (atomic_read(&cpu_buffer->record_disabled)) |
|
goto out; |
|
|
|
if (length > BUF_MAX_DATA_SIZE) |
|
goto out; |
|
|
|
if (unlikely(trace_recursive_lock(cpu_buffer))) |
|
goto out; |
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length); |
|
if (!event) |
|
goto out_unlock; |
|
|
|
body = rb_event_data(event); |
|
|
|
memcpy(body, data, length); |
|
|
|
rb_commit(cpu_buffer, event); |
|
|
|
rb_wakeups(buffer, cpu_buffer); |
|
|
|
ret = 0; |
|
|
|
out_unlock: |
|
trace_recursive_unlock(cpu_buffer); |
|
|
|
out: |
|
preempt_enable_notrace(); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_write); |
|
|
|
static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct buffer_page *reader = cpu_buffer->reader_page; |
|
struct buffer_page *head = rb_set_head_page(cpu_buffer); |
|
struct buffer_page *commit = cpu_buffer->commit_page; |
|
|
|
/* In case of error, head will be NULL */ |
|
if (unlikely(!head)) |
|
return true; |
|
|
|
return reader->read == rb_page_commit(reader) && |
|
(commit == reader || |
|
(commit == head && |
|
head->read == rb_page_commit(commit))); |
|
} |
|
|
|
/** |
|
* ring_buffer_record_disable - stop all writes into the buffer |
|
* @buffer: The ring buffer to stop writes to. |
|
* |
|
* This prevents all writes to the buffer. Any attempt to write |
|
* to the buffer after this will fail and return NULL. |
|
* |
|
* The caller should call synchronize_rcu() after this. |
|
*/ |
|
void ring_buffer_record_disable(struct trace_buffer *buffer) |
|
{ |
|
atomic_inc(&buffer->record_disabled); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
|
|
|
/** |
|
* ring_buffer_record_enable - enable writes to the buffer |
|
* @buffer: The ring buffer to enable writes |
|
* |
|
* Note, multiple disables will need the same number of enables |
|
* to truly enable the writing (much like preempt_disable). |
|
*/ |
|
void ring_buffer_record_enable(struct trace_buffer *buffer) |
|
{ |
|
atomic_dec(&buffer->record_disabled); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
|
|
|
/** |
|
* ring_buffer_record_off - stop all writes into the buffer |
|
* @buffer: The ring buffer to stop writes to. |
|
* |
|
* This prevents all writes to the buffer. Any attempt to write |
|
* to the buffer after this will fail and return NULL. |
|
* |
|
* This is different than ring_buffer_record_disable() as |
|
* it works like an on/off switch, where as the disable() version |
|
* must be paired with a enable(). |
|
*/ |
|
void ring_buffer_record_off(struct trace_buffer *buffer) |
|
{ |
|
unsigned int rd; |
|
unsigned int new_rd; |
|
|
|
do { |
|
rd = atomic_read(&buffer->record_disabled); |
|
new_rd = rd | RB_BUFFER_OFF; |
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_off); |
|
|
|
/** |
|
* ring_buffer_record_on - restart writes into the buffer |
|
* @buffer: The ring buffer to start writes to. |
|
* |
|
* This enables all writes to the buffer that was disabled by |
|
* ring_buffer_record_off(). |
|
* |
|
* This is different than ring_buffer_record_enable() as |
|
* it works like an on/off switch, where as the enable() version |
|
* must be paired with a disable(). |
|
*/ |
|
void ring_buffer_record_on(struct trace_buffer *buffer) |
|
{ |
|
unsigned int rd; |
|
unsigned int new_rd; |
|
|
|
do { |
|
rd = atomic_read(&buffer->record_disabled); |
|
new_rd = rd & ~RB_BUFFER_OFF; |
|
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_on); |
|
|
|
/** |
|
* ring_buffer_record_is_on - return true if the ring buffer can write |
|
* @buffer: The ring buffer to see if write is enabled |
|
* |
|
* Returns true if the ring buffer is in a state that it accepts writes. |
|
*/ |
|
bool ring_buffer_record_is_on(struct trace_buffer *buffer) |
|
{ |
|
return !atomic_read(&buffer->record_disabled); |
|
} |
|
|
|
/** |
|
* ring_buffer_record_is_set_on - return true if the ring buffer is set writable |
|
* @buffer: The ring buffer to see if write is set enabled |
|
* |
|
* Returns true if the ring buffer is set writable by ring_buffer_record_on(). |
|
* Note that this does NOT mean it is in a writable state. |
|
* |
|
* It may return true when the ring buffer has been disabled by |
|
* ring_buffer_record_disable(), as that is a temporary disabling of |
|
* the ring buffer. |
|
*/ |
|
bool ring_buffer_record_is_set_on(struct trace_buffer *buffer) |
|
{ |
|
return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); |
|
} |
|
|
|
/** |
|
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer |
|
* @buffer: The ring buffer to stop writes to. |
|
* @cpu: The CPU buffer to stop |
|
* |
|
* This prevents all writes to the buffer. Any attempt to write |
|
* to the buffer after this will fail and return NULL. |
|
* |
|
* The caller should call synchronize_rcu() after this. |
|
*/ |
|
void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
|
|
|
/** |
|
* ring_buffer_record_enable_cpu - enable writes to the buffer |
|
* @buffer: The ring buffer to enable writes |
|
* @cpu: The CPU to enable. |
|
* |
|
* Note, multiple disables will need the same number of enables |
|
* to truly enable the writing (much like preempt_disable). |
|
*/ |
|
void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
atomic_dec(&cpu_buffer->record_disabled); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
|
|
|
/* |
|
* The total entries in the ring buffer is the running counter |
|
* of entries entered into the ring buffer, minus the sum of |
|
* the entries read from the ring buffer and the number of |
|
* entries that were overwritten. |
|
*/ |
|
static inline unsigned long |
|
rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
return local_read(&cpu_buffer->entries) - |
|
(local_read(&cpu_buffer->overrun) + cpu_buffer->read); |
|
} |
|
|
|
/** |
|
* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to read from. |
|
*/ |
|
u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu) |
|
{ |
|
unsigned long flags; |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct buffer_page *bpage; |
|
u64 ret = 0; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
/* |
|
* if the tail is on reader_page, oldest time stamp is on the reader |
|
* page |
|
*/ |
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
|
bpage = cpu_buffer->reader_page; |
|
else |
|
bpage = rb_set_head_page(cpu_buffer); |
|
if (bpage) |
|
ret = bpage->page->time_stamp; |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); |
|
|
|
/** |
|
* ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to read from. |
|
*/ |
|
unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long ret; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); |
|
|
|
/** |
|
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to get the entries from. |
|
*/ |
|
unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
return rb_num_of_entries(cpu_buffer); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
|
|
|
/** |
|
* ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
|
* buffer wrapping around (only if RB_FL_OVERWRITE is on). |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to get the number of overruns from |
|
*/ |
|
unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long ret; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
ret = local_read(&cpu_buffer->overrun); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
|
|
|
/** |
|
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
|
* commits failing due to the buffer wrapping around while there are uncommitted |
|
* events, such as during an interrupt storm. |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to get the number of overruns from |
|
*/ |
|
unsigned long |
|
ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long ret; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
ret = local_read(&cpu_buffer->commit_overrun); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); |
|
|
|
/** |
|
* ring_buffer_dropped_events_cpu - get the number of dropped events caused by |
|
* the ring buffer filling up (only if RB_FL_OVERWRITE is off). |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to get the number of overruns from |
|
*/ |
|
unsigned long |
|
ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long ret; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
ret = local_read(&cpu_buffer->dropped_events); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); |
|
|
|
/** |
|
* ring_buffer_read_events_cpu - get the number of events successfully read |
|
* @buffer: The ring buffer |
|
* @cpu: The per CPU buffer to get the number of events read |
|
*/ |
|
unsigned long |
|
ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
return cpu_buffer->read; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); |
|
|
|
/** |
|
* ring_buffer_entries - get the number of entries in a buffer |
|
* @buffer: The ring buffer |
|
* |
|
* Returns the total number of entries in the ring buffer |
|
* (all CPU entries) |
|
*/ |
|
unsigned long ring_buffer_entries(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long entries = 0; |
|
int cpu; |
|
|
|
/* if you care about this being correct, lock the buffer */ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
entries += rb_num_of_entries(cpu_buffer); |
|
} |
|
|
|
return entries; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_entries); |
|
|
|
/** |
|
* ring_buffer_overruns - get the number of overruns in buffer |
|
* @buffer: The ring buffer |
|
* |
|
* Returns the total number of overruns in the ring buffer |
|
* (all CPU entries) |
|
*/ |
|
unsigned long ring_buffer_overruns(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long overruns = 0; |
|
int cpu; |
|
|
|
/* if you care about this being correct, lock the buffer */ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
overruns += local_read(&cpu_buffer->overrun); |
|
} |
|
|
|
return overruns; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
|
|
|
static void rb_iter_reset(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
|
|
|
/* Iterator usage is expected to have record disabled */ |
|
iter->head_page = cpu_buffer->reader_page; |
|
iter->head = cpu_buffer->reader_page->read; |
|
iter->next_event = iter->head; |
|
|
|
iter->cache_reader_page = iter->head_page; |
|
iter->cache_read = cpu_buffer->read; |
|
|
|
if (iter->head) { |
|
iter->read_stamp = cpu_buffer->read_stamp; |
|
iter->page_stamp = cpu_buffer->reader_page->page->time_stamp; |
|
} else { |
|
iter->read_stamp = iter->head_page->page->time_stamp; |
|
iter->page_stamp = iter->read_stamp; |
|
} |
|
} |
|
|
|
/** |
|
* ring_buffer_iter_reset - reset an iterator |
|
* @iter: The iterator to reset |
|
* |
|
* Resets the iterator, so that it will start from the beginning |
|
* again. |
|
*/ |
|
void ring_buffer_iter_reset(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long flags; |
|
|
|
if (!iter) |
|
return; |
|
|
|
cpu_buffer = iter->cpu_buffer; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
rb_iter_reset(iter); |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
|
|
|
/** |
|
* ring_buffer_iter_empty - check if an iterator has no more to read |
|
* @iter: The iterator to check |
|
*/ |
|
int ring_buffer_iter_empty(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct buffer_page *reader; |
|
struct buffer_page *head_page; |
|
struct buffer_page *commit_page; |
|
struct buffer_page *curr_commit_page; |
|
unsigned commit; |
|
u64 curr_commit_ts; |
|
u64 commit_ts; |
|
|
|
cpu_buffer = iter->cpu_buffer; |
|
reader = cpu_buffer->reader_page; |
|
head_page = cpu_buffer->head_page; |
|
commit_page = cpu_buffer->commit_page; |
|
commit_ts = commit_page->page->time_stamp; |
|
|
|
/* |
|
* When the writer goes across pages, it issues a cmpxchg which |
|
* is a mb(), which will synchronize with the rmb here. |
|
* (see rb_tail_page_update()) |
|
*/ |
|
smp_rmb(); |
|
commit = rb_page_commit(commit_page); |
|
/* We want to make sure that the commit page doesn't change */ |
|
smp_rmb(); |
|
|
|
/* Make sure commit page didn't change */ |
|
curr_commit_page = READ_ONCE(cpu_buffer->commit_page); |
|
curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp); |
|
|
|
/* If the commit page changed, then there's more data */ |
|
if (curr_commit_page != commit_page || |
|
curr_commit_ts != commit_ts) |
|
return 0; |
|
|
|
/* Still racy, as it may return a false positive, but that's OK */ |
|
return ((iter->head_page == commit_page && iter->head >= commit) || |
|
(iter->head_page == reader && commit_page == head_page && |
|
head_page->read == commit && |
|
iter->head == rb_page_commit(cpu_buffer->reader_page))); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
|
|
|
static void |
|
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
|
struct ring_buffer_event *event) |
|
{ |
|
u64 delta; |
|
|
|
switch (event->type_len) { |
|
case RINGBUF_TYPE_PADDING: |
|
return; |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
delta = ring_buffer_event_time_stamp(event); |
|
cpu_buffer->read_stamp += delta; |
|
return; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
delta = ring_buffer_event_time_stamp(event); |
|
cpu_buffer->read_stamp = delta; |
|
return; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
cpu_buffer->read_stamp += event->time_delta; |
|
return; |
|
|
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); |
|
} |
|
return; |
|
} |
|
|
|
static void |
|
rb_update_iter_read_stamp(struct ring_buffer_iter *iter, |
|
struct ring_buffer_event *event) |
|
{ |
|
u64 delta; |
|
|
|
switch (event->type_len) { |
|
case RINGBUF_TYPE_PADDING: |
|
return; |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
delta = ring_buffer_event_time_stamp(event); |
|
iter->read_stamp += delta; |
|
return; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
delta = ring_buffer_event_time_stamp(event); |
|
iter->read_stamp = delta; |
|
return; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
iter->read_stamp += event->time_delta; |
|
return; |
|
|
|
default: |
|
RB_WARN_ON(iter->cpu_buffer, 1); |
|
} |
|
return; |
|
} |
|
|
|
static struct buffer_page * |
|
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct buffer_page *reader = NULL; |
|
unsigned long overwrite; |
|
unsigned long flags; |
|
int nr_loops = 0; |
|
int ret; |
|
|
|
local_irq_save(flags); |
|
arch_spin_lock(&cpu_buffer->lock); |
|
|
|
again: |
|
/* |
|
* This should normally only loop twice. But because the |
|
* start of the reader inserts an empty page, it causes |
|
* a case where we will loop three times. There should be no |
|
* reason to loop four times (that I know of). |
|
*/ |
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
|
reader = NULL; |
|
goto out; |
|
} |
|
|
|
reader = cpu_buffer->reader_page; |
|
|
|
/* If there's more to read, return this page */ |
|
if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
|
goto out; |
|
|
|
/* Never should we have an index greater than the size */ |
|
if (RB_WARN_ON(cpu_buffer, |
|
cpu_buffer->reader_page->read > rb_page_size(reader))) |
|
goto out; |
|
|
|
/* check if we caught up to the tail */ |
|
reader = NULL; |
|
if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
|
goto out; |
|
|
|
/* Don't bother swapping if the ring buffer is empty */ |
|
if (rb_num_of_entries(cpu_buffer) == 0) |
|
goto out; |
|
|
|
/* |
|
* Reset the reader page to size zero. |
|
*/ |
|
local_set(&cpu_buffer->reader_page->write, 0); |
|
local_set(&cpu_buffer->reader_page->entries, 0); |
|
local_set(&cpu_buffer->reader_page->page->commit, 0); |
|
cpu_buffer->reader_page->real_end = 0; |
|
|
|
spin: |
|
/* |
|
* Splice the empty reader page into the list around the head. |
|
*/ |
|
reader = rb_set_head_page(cpu_buffer); |
|
if (!reader) |
|
goto out; |
|
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
|
cpu_buffer->reader_page->list.prev = reader->list.prev; |
|
|
|
/* |
|
* cpu_buffer->pages just needs to point to the buffer, it |
|
* has no specific buffer page to point to. Lets move it out |
|
* of our way so we don't accidentally swap it. |
|
*/ |
|
cpu_buffer->pages = reader->list.prev; |
|
|
|
/* The reader page will be pointing to the new head */ |
|
rb_set_list_to_head(&cpu_buffer->reader_page->list); |
|
|
|
/* |
|
* We want to make sure we read the overruns after we set up our |
|
* pointers to the next object. The writer side does a |
|
* cmpxchg to cross pages which acts as the mb on the writer |
|
* side. Note, the reader will constantly fail the swap |
|
* while the writer is updating the pointers, so this |
|
* guarantees that the overwrite recorded here is the one we |
|
* want to compare with the last_overrun. |
|
*/ |
|
smp_mb(); |
|
overwrite = local_read(&(cpu_buffer->overrun)); |
|
|
|
/* |
|
* Here's the tricky part. |
|
* |
|
* We need to move the pointer past the header page. |
|
* But we can only do that if a writer is not currently |
|
* moving it. The page before the header page has the |
|
* flag bit '1' set if it is pointing to the page we want. |
|
* but if the writer is in the process of moving it |
|
* than it will be '2' or already moved '0'. |
|
*/ |
|
|
|
ret = rb_head_page_replace(reader, cpu_buffer->reader_page); |
|
|
|
/* |
|
* If we did not convert it, then we must try again. |
|
*/ |
|
if (!ret) |
|
goto spin; |
|
|
|
/* |
|
* Yay! We succeeded in replacing the page. |
|
* |
|
* Now make the new head point back to the reader page. |
|
*/ |
|
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
|
rb_inc_page(&cpu_buffer->head_page); |
|
|
|
local_inc(&cpu_buffer->pages_read); |
|
|
|
/* Finally update the reader page to the new head */ |
|
cpu_buffer->reader_page = reader; |
|
cpu_buffer->reader_page->read = 0; |
|
|
|
if (overwrite != cpu_buffer->last_overrun) { |
|
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; |
|
cpu_buffer->last_overrun = overwrite; |
|
} |
|
|
|
goto again; |
|
|
|
out: |
|
/* Update the read_stamp on the first event */ |
|
if (reader && reader->read == 0) |
|
cpu_buffer->read_stamp = reader->page->time_stamp; |
|
|
|
arch_spin_unlock(&cpu_buffer->lock); |
|
local_irq_restore(flags); |
|
|
|
return reader; |
|
} |
|
|
|
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct buffer_page *reader; |
|
unsigned length; |
|
|
|
reader = rb_get_reader_page(cpu_buffer); |
|
|
|
/* This function should not be called when buffer is empty */ |
|
if (RB_WARN_ON(cpu_buffer, !reader)) |
|
return; |
|
|
|
event = rb_reader_event(cpu_buffer); |
|
|
|
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
|
cpu_buffer->read++; |
|
|
|
rb_update_read_stamp(cpu_buffer, event); |
|
|
|
length = rb_event_length(event); |
|
cpu_buffer->reader_page->read += length; |
|
} |
|
|
|
static void rb_advance_iter(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
|
|
cpu_buffer = iter->cpu_buffer; |
|
|
|
/* If head == next_event then we need to jump to the next event */ |
|
if (iter->head == iter->next_event) { |
|
/* If the event gets overwritten again, there's nothing to do */ |
|
if (rb_iter_head_event(iter) == NULL) |
|
return; |
|
} |
|
|
|
iter->head = iter->next_event; |
|
|
|
/* |
|
* Check if we are at the end of the buffer. |
|
*/ |
|
if (iter->next_event >= rb_page_size(iter->head_page)) { |
|
/* discarded commits can make the page empty */ |
|
if (iter->head_page == cpu_buffer->commit_page) |
|
return; |
|
rb_inc_iter(iter); |
|
return; |
|
} |
|
|
|
rb_update_iter_read_stamp(iter, iter->event); |
|
} |
|
|
|
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
return cpu_buffer->lost_events; |
|
} |
|
|
|
static struct ring_buffer_event * |
|
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
|
unsigned long *lost_events) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct buffer_page *reader; |
|
int nr_loops = 0; |
|
|
|
if (ts) |
|
*ts = 0; |
|
again: |
|
/* |
|
* We repeat when a time extend is encountered. |
|
* Since the time extend is always attached to a data event, |
|
* we should never loop more than once. |
|
* (We never hit the following condition more than twice). |
|
*/ |
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
|
return NULL; |
|
|
|
reader = rb_get_reader_page(cpu_buffer); |
|
if (!reader) |
|
return NULL; |
|
|
|
event = rb_reader_event(cpu_buffer); |
|
|
|
switch (event->type_len) { |
|
case RINGBUF_TYPE_PADDING: |
|
if (rb_null_event(event)) |
|
RB_WARN_ON(cpu_buffer, 1); |
|
/* |
|
* Because the writer could be discarding every |
|
* event it creates (which would probably be bad) |
|
* if we were to go back to "again" then we may never |
|
* catch up, and will trigger the warn on, or lock |
|
* the box. Return the padding, and we will release |
|
* the current locks, and try again. |
|
*/ |
|
return event; |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
/* Internal data, OK to advance */ |
|
rb_advance_reader(cpu_buffer); |
|
goto again; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
if (ts) { |
|
*ts = ring_buffer_event_time_stamp(event); |
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
|
cpu_buffer->cpu, ts); |
|
} |
|
/* Internal data, OK to advance */ |
|
rb_advance_reader(cpu_buffer); |
|
goto again; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
if (ts && !(*ts)) { |
|
*ts = cpu_buffer->read_stamp + event->time_delta; |
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
|
cpu_buffer->cpu, ts); |
|
} |
|
if (lost_events) |
|
*lost_events = rb_lost_events(cpu_buffer); |
|
return event; |
|
|
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); |
|
} |
|
|
|
return NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_peek); |
|
|
|
static struct ring_buffer_event * |
|
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) |
|
{ |
|
struct trace_buffer *buffer; |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct ring_buffer_event *event; |
|
int nr_loops = 0; |
|
|
|
if (ts) |
|
*ts = 0; |
|
|
|
cpu_buffer = iter->cpu_buffer; |
|
buffer = cpu_buffer->buffer; |
|
|
|
/* |
|
* Check if someone performed a consuming read to |
|
* the buffer. A consuming read invalidates the iterator |
|
* and we need to reset the iterator in this case. |
|
*/ |
|
if (unlikely(iter->cache_read != cpu_buffer->read || |
|
iter->cache_reader_page != cpu_buffer->reader_page)) |
|
rb_iter_reset(iter); |
|
|
|
again: |
|
if (ring_buffer_iter_empty(iter)) |
|
return NULL; |
|
|
|
/* |
|
* As the writer can mess with what the iterator is trying |
|
* to read, just give up if we fail to get an event after |
|
* three tries. The iterator is not as reliable when reading |
|
* the ring buffer with an active write as the consumer is. |
|
* Do not warn if the three failures is reached. |
|
*/ |
|
if (++nr_loops > 3) |
|
return NULL; |
|
|
|
if (rb_per_cpu_empty(cpu_buffer)) |
|
return NULL; |
|
|
|
if (iter->head >= rb_page_size(iter->head_page)) { |
|
rb_inc_iter(iter); |
|
goto again; |
|
} |
|
|
|
event = rb_iter_head_event(iter); |
|
if (!event) |
|
goto again; |
|
|
|
switch (event->type_len) { |
|
case RINGBUF_TYPE_PADDING: |
|
if (rb_null_event(event)) { |
|
rb_inc_iter(iter); |
|
goto again; |
|
} |
|
rb_advance_iter(iter); |
|
return event; |
|
|
|
case RINGBUF_TYPE_TIME_EXTEND: |
|
/* Internal data, OK to advance */ |
|
rb_advance_iter(iter); |
|
goto again; |
|
|
|
case RINGBUF_TYPE_TIME_STAMP: |
|
if (ts) { |
|
*ts = ring_buffer_event_time_stamp(event); |
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
|
cpu_buffer->cpu, ts); |
|
} |
|
/* Internal data, OK to advance */ |
|
rb_advance_iter(iter); |
|
goto again; |
|
|
|
case RINGBUF_TYPE_DATA: |
|
if (ts && !(*ts)) { |
|
*ts = iter->read_stamp + event->time_delta; |
|
ring_buffer_normalize_time_stamp(buffer, |
|
cpu_buffer->cpu, ts); |
|
} |
|
return event; |
|
|
|
default: |
|
RB_WARN_ON(cpu_buffer, 1); |
|
} |
|
|
|
return NULL; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
|
|
|
static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
if (likely(!in_nmi())) { |
|
raw_spin_lock(&cpu_buffer->reader_lock); |
|
return true; |
|
} |
|
|
|
/* |
|
* If an NMI die dumps out the content of the ring buffer |
|
* trylock must be used to prevent a deadlock if the NMI |
|
* preempted a task that holds the ring buffer locks. If |
|
* we get the lock then all is fine, if not, then continue |
|
* to do the read, but this can corrupt the ring buffer, |
|
* so it must be permanently disabled from future writes. |
|
* Reading from NMI is a oneshot deal. |
|
*/ |
|
if (raw_spin_trylock(&cpu_buffer->reader_lock)) |
|
return true; |
|
|
|
/* Continue without locking, but disable the ring buffer */ |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
return false; |
|
} |
|
|
|
static inline void |
|
rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) |
|
{ |
|
if (likely(locked)) |
|
raw_spin_unlock(&cpu_buffer->reader_lock); |
|
return; |
|
} |
|
|
|
/** |
|
* ring_buffer_peek - peek at the next event to be read |
|
* @buffer: The ring buffer to read |
|
* @cpu: The cpu to peak at |
|
* @ts: The timestamp counter of this event. |
|
* @lost_events: a variable to store if events were lost (may be NULL) |
|
* |
|
* This will return the event that will be read next, but does |
|
* not consume the data. |
|
*/ |
|
struct ring_buffer_event * |
|
ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts, |
|
unsigned long *lost_events) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
|
struct ring_buffer_event *event; |
|
unsigned long flags; |
|
bool dolock; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return NULL; |
|
|
|
again: |
|
local_irq_save(flags); |
|
dolock = rb_reader_lock(cpu_buffer); |
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
|
if (event && event->type_len == RINGBUF_TYPE_PADDING) |
|
rb_advance_reader(cpu_buffer); |
|
rb_reader_unlock(cpu_buffer, dolock); |
|
local_irq_restore(flags); |
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING) |
|
goto again; |
|
|
|
return event; |
|
} |
|
|
|
/** ring_buffer_iter_dropped - report if there are dropped events |
|
* @iter: The ring buffer iterator |
|
* |
|
* Returns true if there was dropped events since the last peek. |
|
*/ |
|
bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter) |
|
{ |
|
bool ret = iter->missed_events != 0; |
|
|
|
iter->missed_events = 0; |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped); |
|
|
|
/** |
|
* ring_buffer_iter_peek - peek at the next event to be read |
|
* @iter: The ring buffer iterator |
|
* @ts: The timestamp counter of this event. |
|
* |
|
* This will return the event that will be read next, but does |
|
* not increment the iterator. |
|
*/ |
|
struct ring_buffer_event * |
|
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
|
struct ring_buffer_event *event; |
|
unsigned long flags; |
|
|
|
again: |
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
event = rb_iter_peek(iter, ts); |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING) |
|
goto again; |
|
|
|
return event; |
|
} |
|
|
|
/** |
|
* ring_buffer_consume - return an event and consume it |
|
* @buffer: The ring buffer to get the next event from |
|
* @cpu: the cpu to read the buffer from |
|
* @ts: a variable to store the timestamp (may be NULL) |
|
* @lost_events: a variable to store if events were lost (may be NULL) |
|
* |
|
* Returns the next event in the ring buffer, and that event is consumed. |
|
* Meaning, that sequential reads will keep returning a different event, |
|
* and eventually empty the ring buffer if the producer is slower. |
|
*/ |
|
struct ring_buffer_event * |
|
ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts, |
|
unsigned long *lost_events) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct ring_buffer_event *event = NULL; |
|
unsigned long flags; |
|
bool dolock; |
|
|
|
again: |
|
/* might be called in atomic */ |
|
preempt_disable(); |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
goto out; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
local_irq_save(flags); |
|
dolock = rb_reader_lock(cpu_buffer); |
|
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
|
if (event) { |
|
cpu_buffer->lost_events = 0; |
|
rb_advance_reader(cpu_buffer); |
|
} |
|
|
|
rb_reader_unlock(cpu_buffer, dolock); |
|
local_irq_restore(flags); |
|
|
|
out: |
|
preempt_enable(); |
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING) |
|
goto again; |
|
|
|
return event; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_consume); |
|
|
|
/** |
|
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
|
* @buffer: The ring buffer to read from |
|
* @cpu: The cpu buffer to iterate over |
|
* @flags: gfp flags to use for memory allocation |
|
* |
|
* This performs the initial preparations necessary to iterate |
|
* through the buffer. Memory is allocated, buffer recording |
|
* is disabled, and the iterator pointer is returned to the caller. |
|
* |
|
* Disabling buffer recording prevents the reading from being |
|
* corrupted. This is not a consuming read, so a producer is not |
|
* expected. |
|
* |
|
* After a sequence of ring_buffer_read_prepare calls, the user is |
|
* expected to make at least one call to ring_buffer_read_prepare_sync. |
|
* Afterwards, ring_buffer_read_start is invoked to get things going |
|
* for real. |
|
* |
|
* This overall must be paired with ring_buffer_read_finish. |
|
*/ |
|
struct ring_buffer_iter * |
|
ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct ring_buffer_iter *iter; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return NULL; |
|
|
|
iter = kzalloc(sizeof(*iter), flags); |
|
if (!iter) |
|
return NULL; |
|
|
|
iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags); |
|
if (!iter->event) { |
|
kfree(iter); |
|
return NULL; |
|
} |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
iter->cpu_buffer = cpu_buffer; |
|
|
|
atomic_inc(&cpu_buffer->resize_disabled); |
|
|
|
return iter; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); |
|
|
|
/** |
|
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls |
|
* |
|
* All previously invoked ring_buffer_read_prepare calls to prepare |
|
* iterators will be synchronized. Afterwards, read_buffer_read_start |
|
* calls on those iterators are allowed. |
|
*/ |
|
void |
|
ring_buffer_read_prepare_sync(void) |
|
{ |
|
synchronize_rcu(); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); |
|
|
|
/** |
|
* ring_buffer_read_start - start a non consuming read of the buffer |
|
* @iter: The iterator returned by ring_buffer_read_prepare |
|
* |
|
* This finalizes the startup of an iteration through the buffer. |
|
* The iterator comes from a call to ring_buffer_read_prepare and |
|
* an intervening ring_buffer_read_prepare_sync must have been |
|
* performed. |
|
* |
|
* Must be paired with ring_buffer_read_finish. |
|
*/ |
|
void |
|
ring_buffer_read_start(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long flags; |
|
|
|
if (!iter) |
|
return; |
|
|
|
cpu_buffer = iter->cpu_buffer; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
arch_spin_lock(&cpu_buffer->lock); |
|
rb_iter_reset(iter); |
|
arch_spin_unlock(&cpu_buffer->lock); |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
|
|
|
/** |
|
* ring_buffer_read_finish - finish reading the iterator of the buffer |
|
* @iter: The iterator retrieved by ring_buffer_start |
|
* |
|
* This re-enables the recording to the buffer, and frees the |
|
* iterator. |
|
*/ |
|
void |
|
ring_buffer_read_finish(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
|
unsigned long flags; |
|
|
|
/* |
|
* Ring buffer is disabled from recording, here's a good place |
|
* to check the integrity of the ring buffer. |
|
* Must prevent readers from trying to read, as the check |
|
* clears the HEAD page and readers require it. |
|
*/ |
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
rb_check_pages(cpu_buffer); |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
|
|
atomic_dec(&cpu_buffer->resize_disabled); |
|
kfree(iter->event); |
|
kfree(iter); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
|
|
|
/** |
|
* ring_buffer_iter_advance - advance the iterator to the next location |
|
* @iter: The ring buffer iterator |
|
* |
|
* Move the location of the iterator such that the next read will |
|
* be the next location of the iterator. |
|
*/ |
|
void ring_buffer_iter_advance(struct ring_buffer_iter *iter) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
|
unsigned long flags; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
|
|
rb_advance_iter(iter); |
|
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_advance); |
|
|
|
/** |
|
* ring_buffer_size - return the size of the ring buffer (in bytes) |
|
* @buffer: The ring buffer. |
|
* @cpu: The CPU to get ring buffer size from. |
|
*/ |
|
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu) |
|
{ |
|
/* |
|
* Earlier, this method returned |
|
* BUF_PAGE_SIZE * buffer->nr_pages |
|
* Since the nr_pages field is now removed, we have converted this to |
|
* return the per cpu buffer value. |
|
*/ |
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_size); |
|
|
|
static void |
|
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
rb_head_page_deactivate(cpu_buffer); |
|
|
|
cpu_buffer->head_page |
|
= list_entry(cpu_buffer->pages, struct buffer_page, list); |
|
local_set(&cpu_buffer->head_page->write, 0); |
|
local_set(&cpu_buffer->head_page->entries, 0); |
|
local_set(&cpu_buffer->head_page->page->commit, 0); |
|
|
|
cpu_buffer->head_page->read = 0; |
|
|
|
cpu_buffer->tail_page = cpu_buffer->head_page; |
|
cpu_buffer->commit_page = cpu_buffer->head_page; |
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
|
INIT_LIST_HEAD(&cpu_buffer->new_pages); |
|
local_set(&cpu_buffer->reader_page->write, 0); |
|
local_set(&cpu_buffer->reader_page->entries, 0); |
|
local_set(&cpu_buffer->reader_page->page->commit, 0); |
|
cpu_buffer->reader_page->read = 0; |
|
|
|
local_set(&cpu_buffer->entries_bytes, 0); |
|
local_set(&cpu_buffer->overrun, 0); |
|
local_set(&cpu_buffer->commit_overrun, 0); |
|
local_set(&cpu_buffer->dropped_events, 0); |
|
local_set(&cpu_buffer->entries, 0); |
|
local_set(&cpu_buffer->committing, 0); |
|
local_set(&cpu_buffer->commits, 0); |
|
local_set(&cpu_buffer->pages_touched, 0); |
|
local_set(&cpu_buffer->pages_read, 0); |
|
cpu_buffer->last_pages_touch = 0; |
|
cpu_buffer->shortest_full = 0; |
|
cpu_buffer->read = 0; |
|
cpu_buffer->read_bytes = 0; |
|
|
|
rb_time_set(&cpu_buffer->write_stamp, 0); |
|
rb_time_set(&cpu_buffer->before_stamp, 0); |
|
|
|
cpu_buffer->lost_events = 0; |
|
cpu_buffer->last_overrun = 0; |
|
|
|
rb_head_page_activate(cpu_buffer); |
|
} |
|
|
|
/* Must have disabled the cpu buffer then done a synchronize_rcu */ |
|
static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) |
|
{ |
|
unsigned long flags; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
|
|
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
|
goto out; |
|
|
|
arch_spin_lock(&cpu_buffer->lock); |
|
|
|
rb_reset_cpu(cpu_buffer); |
|
|
|
arch_spin_unlock(&cpu_buffer->lock); |
|
|
|
out: |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
} |
|
|
|
/** |
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer |
|
* @buffer: The ring buffer to reset a per cpu buffer of |
|
* @cpu: The CPU buffer to be reset |
|
*/ |
|
void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return; |
|
|
|
/* prevent another thread from changing buffer sizes */ |
|
mutex_lock(&buffer->mutex); |
|
|
|
atomic_inc(&cpu_buffer->resize_disabled); |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
|
|
/* Make sure all commits have finished */ |
|
synchronize_rcu(); |
|
|
|
reset_disabled_cpu_buffer(cpu_buffer); |
|
|
|
atomic_dec(&cpu_buffer->record_disabled); |
|
atomic_dec(&cpu_buffer->resize_disabled); |
|
|
|
mutex_unlock(&buffer->mutex); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
|
|
|
/** |
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer |
|
* @buffer: The ring buffer to reset a per cpu buffer of |
|
* @cpu: The CPU buffer to be reset |
|
*/ |
|
void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu; |
|
|
|
/* prevent another thread from changing buffer sizes */ |
|
mutex_lock(&buffer->mutex); |
|
|
|
for_each_online_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
atomic_inc(&cpu_buffer->resize_disabled); |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
} |
|
|
|
/* Make sure all commits have finished */ |
|
synchronize_rcu(); |
|
|
|
for_each_online_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
reset_disabled_cpu_buffer(cpu_buffer); |
|
|
|
atomic_dec(&cpu_buffer->record_disabled); |
|
atomic_dec(&cpu_buffer->resize_disabled); |
|
} |
|
|
|
mutex_unlock(&buffer->mutex); |
|
} |
|
|
|
/** |
|
* ring_buffer_reset - reset a ring buffer |
|
* @buffer: The ring buffer to reset all cpu buffers |
|
*/ |
|
void ring_buffer_reset(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
int cpu; |
|
|
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
atomic_inc(&cpu_buffer->resize_disabled); |
|
atomic_inc(&cpu_buffer->record_disabled); |
|
} |
|
|
|
/* Make sure all commits have finished */ |
|
synchronize_rcu(); |
|
|
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
|
|
reset_disabled_cpu_buffer(cpu_buffer); |
|
|
|
atomic_dec(&cpu_buffer->record_disabled); |
|
atomic_dec(&cpu_buffer->resize_disabled); |
|
} |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_reset); |
|
|
|
/** |
|
* rind_buffer_empty - is the ring buffer empty? |
|
* @buffer: The ring buffer to test |
|
*/ |
|
bool ring_buffer_empty(struct trace_buffer *buffer) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long flags; |
|
bool dolock; |
|
int cpu; |
|
int ret; |
|
|
|
/* yes this is racy, but if you don't like the race, lock the buffer */ |
|
for_each_buffer_cpu(buffer, cpu) { |
|
cpu_buffer = buffer->buffers[cpu]; |
|
local_irq_save(flags); |
|
dolock = rb_reader_lock(cpu_buffer); |
|
ret = rb_per_cpu_empty(cpu_buffer); |
|
rb_reader_unlock(cpu_buffer, dolock); |
|
local_irq_restore(flags); |
|
|
|
if (!ret) |
|
return false; |
|
} |
|
|
|
return true; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_empty); |
|
|
|
/** |
|
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? |
|
* @buffer: The ring buffer |
|
* @cpu: The CPU buffer to test |
|
*/ |
|
bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
unsigned long flags; |
|
bool dolock; |
|
int ret; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return true; |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
local_irq_save(flags); |
|
dolock = rb_reader_lock(cpu_buffer); |
|
ret = rb_per_cpu_empty(cpu_buffer); |
|
rb_reader_unlock(cpu_buffer, dolock); |
|
local_irq_restore(flags); |
|
|
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
|
/** |
|
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers |
|
* @buffer_a: One buffer to swap with |
|
* @buffer_b: The other buffer to swap with |
|
* @cpu: the CPU of the buffers to swap |
|
* |
|
* This function is useful for tracers that want to take a "snapshot" |
|
* of a CPU buffer and has another back up buffer lying around. |
|
* it is expected that the tracer handles the cpu buffer not being |
|
* used at the moment. |
|
*/ |
|
int ring_buffer_swap_cpu(struct trace_buffer *buffer_a, |
|
struct trace_buffer *buffer_b, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer_a; |
|
struct ring_buffer_per_cpu *cpu_buffer_b; |
|
int ret = -EINVAL; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
|
!cpumask_test_cpu(cpu, buffer_b->cpumask)) |
|
goto out; |
|
|
|
cpu_buffer_a = buffer_a->buffers[cpu]; |
|
cpu_buffer_b = buffer_b->buffers[cpu]; |
|
|
|
/* At least make sure the two buffers are somewhat the same */ |
|
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) |
|
goto out; |
|
|
|
ret = -EAGAIN; |
|
|
|
if (atomic_read(&buffer_a->record_disabled)) |
|
goto out; |
|
|
|
if (atomic_read(&buffer_b->record_disabled)) |
|
goto out; |
|
|
|
if (atomic_read(&cpu_buffer_a->record_disabled)) |
|
goto out; |
|
|
|
if (atomic_read(&cpu_buffer_b->record_disabled)) |
|
goto out; |
|
|
|
/* |
|
* We can't do a synchronize_rcu here because this |
|
* function can be called in atomic context. |
|
* Normally this will be called from the same CPU as cpu. |
|
* If not it's up to the caller to protect this. |
|
*/ |
|
atomic_inc(&cpu_buffer_a->record_disabled); |
|
atomic_inc(&cpu_buffer_b->record_disabled); |
|
|
|
ret = -EBUSY; |
|
if (local_read(&cpu_buffer_a->committing)) |
|
goto out_dec; |
|
if (local_read(&cpu_buffer_b->committing)) |
|
goto out_dec; |
|
|
|
buffer_a->buffers[cpu] = cpu_buffer_b; |
|
buffer_b->buffers[cpu] = cpu_buffer_a; |
|
|
|
cpu_buffer_b->buffer = buffer_a; |
|
cpu_buffer_a->buffer = buffer_b; |
|
|
|
ret = 0; |
|
|
|
out_dec: |
|
atomic_dec(&cpu_buffer_a->record_disabled); |
|
atomic_dec(&cpu_buffer_b->record_disabled); |
|
out: |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
|
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
|
|
|
/** |
|
* ring_buffer_alloc_read_page - allocate a page to read from buffer |
|
* @buffer: the buffer to allocate for. |
|
* @cpu: the cpu buffer to allocate. |
|
* |
|
* This function is used in conjunction with ring_buffer_read_page. |
|
* When reading a full page from the ring buffer, these functions |
|
* can be used to speed up the process. The calling function should |
|
* allocate a few pages first with this function. Then when it |
|
* needs to get pages from the ring buffer, it passes the result |
|
* of this function into ring_buffer_read_page, which will swap |
|
* the page that was allocated, with the read page of the buffer. |
|
* |
|
* Returns: |
|
* The page allocated, or ERR_PTR |
|
*/ |
|
void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer; |
|
struct buffer_data_page *bpage = NULL; |
|
unsigned long flags; |
|
struct page *page; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return ERR_PTR(-ENODEV); |
|
|
|
cpu_buffer = buffer->buffers[cpu]; |
|
local_irq_save(flags); |
|
arch_spin_lock(&cpu_buffer->lock); |
|
|
|
if (cpu_buffer->free_page) { |
|
bpage = cpu_buffer->free_page; |
|
cpu_buffer->free_page = NULL; |
|
} |
|
|
|
arch_spin_unlock(&cpu_buffer->lock); |
|
local_irq_restore(flags); |
|
|
|
if (bpage) |
|
goto out; |
|
|
|
page = alloc_pages_node(cpu_to_node(cpu), |
|
GFP_KERNEL | __GFP_NORETRY, 0); |
|
if (!page) |
|
return ERR_PTR(-ENOMEM); |
|
|
|
bpage = page_address(page); |
|
|
|
out: |
|
rb_init_page(bpage); |
|
|
|
return bpage; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
|
|
|
/** |
|
* ring_buffer_free_read_page - free an allocated read page |
|
* @buffer: the buffer the page was allocate for |
|
* @cpu: the cpu buffer the page came from |
|
* @data: the page to free |
|
* |
|
* Free a page allocated from ring_buffer_alloc_read_page. |
|
*/ |
|
void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
|
struct buffer_data_page *bpage = data; |
|
struct page *page = virt_to_page(bpage); |
|
unsigned long flags; |
|
|
|
/* If the page is still in use someplace else, we can't reuse it */ |
|
if (page_ref_count(page) > 1) |
|
goto out; |
|
|
|
local_irq_save(flags); |
|
arch_spin_lock(&cpu_buffer->lock); |
|
|
|
if (!cpu_buffer->free_page) { |
|
cpu_buffer->free_page = bpage; |
|
bpage = NULL; |
|
} |
|
|
|
arch_spin_unlock(&cpu_buffer->lock); |
|
local_irq_restore(flags); |
|
|
|
out: |
|
free_page((unsigned long)bpage); |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
|
|
|
/** |
|
* ring_buffer_read_page - extract a page from the ring buffer |
|
* @buffer: buffer to extract from |
|
* @data_page: the page to use allocated from ring_buffer_alloc_read_page |
|
* @len: amount to extract |
|
* @cpu: the cpu of the buffer to extract |
|
* @full: should the extraction only happen when the page is full. |
|
* |
|
* This function will pull out a page from the ring buffer and consume it. |
|
* @data_page must be the address of the variable that was returned |
|
* from ring_buffer_alloc_read_page. This is because the page might be used |
|
* to swap with a page in the ring buffer. |
|
* |
|
* for example: |
|
* rpage = ring_buffer_alloc_read_page(buffer, cpu); |
|
* if (IS_ERR(rpage)) |
|
* return PTR_ERR(rpage); |
|
* ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
|
* if (ret >= 0) |
|
* process_page(rpage, ret); |
|
* |
|
* When @full is set, the function will not return true unless |
|
* the writer is off the reader page. |
|
* |
|
* Note: it is up to the calling functions to handle sleeps and wakeups. |
|
* The ring buffer can be used anywhere in the kernel and can not |
|
* blindly call wake_up. The layer that uses the ring buffer must be |
|
* responsible for that. |
|
* |
|
* Returns: |
|
* >=0 if data has been transferred, returns the offset of consumed data. |
|
* <0 if no data has been transferred. |
|
*/ |
|
int ring_buffer_read_page(struct trace_buffer *buffer, |
|
void **data_page, size_t len, int cpu, int full) |
|
{ |
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
|
struct ring_buffer_event *event; |
|
struct buffer_data_page *bpage; |
|
struct buffer_page *reader; |
|
unsigned long missed_events; |
|
unsigned long flags; |
|
unsigned int commit; |
|
unsigned int read; |
|
u64 save_timestamp; |
|
int ret = -1; |
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
|
goto out; |
|
|
|
/* |
|
* If len is not big enough to hold the page header, then |
|
* we can not copy anything. |
|
*/ |
|
if (len <= BUF_PAGE_HDR_SIZE) |
|
goto out; |
|
|
|
len -= BUF_PAGE_HDR_SIZE; |
|
|
|
if (!data_page) |
|
goto out; |
|
|
|
bpage = *data_page; |
|
if (!bpage) |
|
goto out; |
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
|
|
|
reader = rb_get_reader_page(cpu_buffer); |
|
if (!reader) |
|
goto out_unlock; |
|
|
|
event = rb_reader_event(cpu_buffer); |
|
|
|
read = reader->read; |
|
commit = rb_page_commit(reader); |
|
|
|
/* Check if any events were dropped */ |
|
missed_events = cpu_buffer->lost_events; |
|
|
|
/* |
|
* If this page has been partially read or |
|
* if len is not big enough to read the rest of the page or |
|
* a writer is still on the page, then |
|
* we must copy the data from the page to the buffer. |
|
* Otherwise, we can simply swap the page with the one passed in. |
|
*/ |
|
if (read || (len < (commit - read)) || |
|
cpu_buffer->reader_page == cpu_buffer->commit_page) { |
|
struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
|
unsigned int rpos = read; |
|
unsigned int pos = 0; |
|
unsigned int size; |
|
|
|
if (full) |
|
goto out_unlock; |
|
|
|
if (len > (commit - read)) |
|
len = (commit - read); |
|
|
|
/* Always keep the time extend and data together */ |
|
size = rb_event_ts_length(event); |
|
|
|
if (len < size) |
|
goto out_unlock; |
|
|
|
/* save the current timestamp, since the user will need it */ |
|
save_timestamp = cpu_buffer->read_stamp; |
|
|
|
/* Need to copy one event at a time */ |
|
do { |
|
/* We need the size of one event, because |
|
* rb_advance_reader only advances by one event, |
|
* whereas rb_event_ts_length may include the size of |
|
* one or two events. |
|
* We have already ensured there's enough space if this |
|
* is a time extend. */ |
|
size = rb_event_length(event); |
|
memcpy(bpage->data + pos, rpage->data + rpos, size); |
|
|
|
len -= size; |
|
|
|
rb_advance_reader(cpu_buffer); |
|
rpos = reader->read; |
|
pos += size; |
|
|
|
if (rpos >= commit) |
|
break; |
|
|
|
event = rb_reader_event(cpu_buffer); |
|
/* Always keep the time extend and data together */ |
|
size = rb_event_ts_length(event); |
|
} while (len >= size); |
|
|
|
/* update bpage */ |
|
local_set(&bpage->commit, pos); |
|
bpage->time_stamp = save_timestamp; |
|
|
|
/* we copied everything to the beginning */ |
|
read = 0; |
|
} else { |
|
/* update the entry counter */ |
|
cpu_buffer->read += rb_page_entries(reader); |
|
cpu_buffer->read_bytes += BUF_PAGE_SIZE; |
|
|
|
/* swap the pages */ |
|
rb_init_page(bpage); |
|
bpage = reader->page; |
|
reader->page = *data_page; |
|
local_set(&reader->write, 0); |
|
local_set(&reader->entries, 0); |
|
reader->read = 0; |
|
*data_page = bpage; |
|
|
|
/* |
|
* Use the real_end for the data size, |
|
* This gives us a chance to store the lost events |
|
* on the page. |
|
*/ |
|
if (reader->real_end) |
|
local_set(&bpage->commit, reader->real_end); |
|
} |
|
ret = read; |
|
|
|
cpu_buffer->lost_events = 0; |
|
|
|
commit = local_read(&bpage->commit); |
|
/* |
|
* Set a flag in the commit field if we lost events |
|
*/ |
|
if (missed_events) { |
|
/* If there is room at the end of the page to save the |
|
* missed events, then record it there. |
|
*/ |
|
if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { |
|
memcpy(&bpage->data[commit], &missed_events, |
|
sizeof(missed_events)); |
|
local_add(RB_MISSED_STORED, &bpage->commit); |
|
commit += sizeof(missed_events); |
|
} |
|
local_add(RB_MISSED_EVENTS, &bpage->commit); |
|
} |
|
|
|
/* |
|
* This page may be off to user land. Zero it out here. |
|
*/ |
|
if (commit < BUF_PAGE_SIZE) |
|
memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); |
|
|
|
out_unlock: |
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
|
|
|
out: |
|
return ret; |
|
} |
|
EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
|
|
|
/* |
|
* We only allocate new buffers, never free them if the CPU goes down. |
|
* If we were to free the buffer, then the user would lose any trace that was in |
|
* the buffer. |
|
*/ |
|
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node) |
|
{ |
|
struct trace_buffer *buffer; |
|
long nr_pages_same; |
|
int cpu_i; |
|
unsigned long nr_pages; |
|
|
|
buffer = container_of(node, struct trace_buffer, node); |
|
if (cpumask_test_cpu(cpu, buffer->cpumask)) |
|
return 0; |
|
|
|
nr_pages = 0; |
|
nr_pages_same = 1; |
|
/* check if all cpu sizes are same */ |
|
for_each_buffer_cpu(buffer, cpu_i) { |
|
/* fill in the size from first enabled cpu */ |
|
if (nr_pages == 0) |
|
nr_pages = buffer->buffers[cpu_i]->nr_pages; |
|
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { |
|
nr_pages_same = 0; |
|
break; |
|
} |
|
} |
|
/* allocate minimum pages, user can later expand it */ |
|
if (!nr_pages_same) |
|
nr_pages = 2; |
|
buffer->buffers[cpu] = |
|
rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
|
if (!buffer->buffers[cpu]) { |
|
WARN(1, "failed to allocate ring buffer on CPU %u\n", |
|
cpu); |
|
return -ENOMEM; |
|
} |
|
smp_wmb(); |
|
cpumask_set_cpu(cpu, buffer->cpumask); |
|
return 0; |
|
} |
|
|
|
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST |
|
/* |
|
* This is a basic integrity check of the ring buffer. |
|
* Late in the boot cycle this test will run when configured in. |
|
* It will kick off a thread per CPU that will go into a loop |
|
* writing to the per cpu ring buffer various sizes of data. |
|
* Some of the data will be large items, some small. |
|
* |
|
* Another thread is created that goes into a spin, sending out |
|
* IPIs to the other CPUs to also write into the ring buffer. |
|
* this is to test the nesting ability of the buffer. |
|
* |
|
* Basic stats are recorded and reported. If something in the |
|
* ring buffer should happen that's not expected, a big warning |
|
* is displayed and all ring buffers are disabled. |
|
*/ |
|
static struct task_struct *rb_threads[NR_CPUS] __initdata; |
|
|
|
struct rb_test_data { |
|
struct trace_buffer *buffer; |
|
unsigned long events; |
|
unsigned long bytes_written; |
|
unsigned long bytes_alloc; |
|
unsigned long bytes_dropped; |
|
unsigned long events_nested; |
|
unsigned long bytes_written_nested; |
|
unsigned long bytes_alloc_nested; |
|
unsigned long bytes_dropped_nested; |
|
int min_size_nested; |
|
int max_size_nested; |
|
int max_size; |
|
int min_size; |
|
int cpu; |
|
int cnt; |
|
}; |
|
|
|
static struct rb_test_data rb_data[NR_CPUS] __initdata; |
|
|
|
/* 1 meg per cpu */ |
|
#define RB_TEST_BUFFER_SIZE 1048576 |
|
|
|
static char rb_string[] __initdata = |
|
"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" |
|
"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" |
|
"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; |
|
|
|
static bool rb_test_started __initdata; |
|
|
|
struct rb_item { |
|
int size; |
|
char str[]; |
|
}; |
|
|
|
static __init int rb_write_something(struct rb_test_data *data, bool nested) |
|
{ |
|
struct ring_buffer_event *event; |
|
struct rb_item *item; |
|
bool started; |
|
int event_len; |
|
int size; |
|
int len; |
|
int cnt; |
|
|
|
/* Have nested writes different that what is written */ |
|
cnt = data->cnt + (nested ? 27 : 0); |
|
|
|
/* Multiply cnt by ~e, to make some unique increment */ |
|
size = (cnt * 68 / 25) % (sizeof(rb_string) - 1); |
|
|
|
len = size + sizeof(struct rb_item); |
|
|
|
started = rb_test_started; |
|
/* read rb_test_started before checking buffer enabled */ |
|
smp_rmb(); |
|
|
|
event = ring_buffer_lock_reserve(data->buffer, len); |
|
if (!event) { |
|
/* Ignore dropped events before test starts. */ |
|
if (started) { |
|
if (nested) |
|
data->bytes_dropped += len; |
|
else |
|
data->bytes_dropped_nested += len; |
|
} |
|
return len; |
|
} |
|
|
|
event_len = ring_buffer_event_length(event); |
|
|
|
if (RB_WARN_ON(data->buffer, event_len < len)) |
|
goto out; |
|
|
|
item = ring_buffer_event_data(event); |
|
item->size = size; |
|
memcpy(item->str, rb_string, size); |
|
|
|
if (nested) { |
|
data->bytes_alloc_nested += event_len; |
|
data->bytes_written_nested += len; |
|
data->events_nested++; |
|
if (!data->min_size_nested || len < data->min_size_nested) |
|
data->min_size_nested = len; |
|
if (len > data->max_size_nested) |
|
data->max_size_nested = len; |
|
} else { |
|
data->bytes_alloc += event_len; |
|
data->bytes_written += len; |
|
data->events++; |
|
if (!data->min_size || len < data->min_size) |
|
data->max_size = len; |
|
if (len > data->max_size) |
|
data->max_size = len; |
|
} |
|
|
|
out: |
|
ring_buffer_unlock_commit(data->buffer, event); |
|
|
|
return 0; |
|
} |
|
|
|
static __init int rb_test(void *arg) |
|
{ |
|
struct rb_test_data *data = arg; |
|
|
|
while (!kthread_should_stop()) { |
|
rb_write_something(data, false); |
|
data->cnt++; |
|
|
|
set_current_state(TASK_INTERRUPTIBLE); |
|
/* Now sleep between a min of 100-300us and a max of 1ms */ |
|
usleep_range(((data->cnt % 3) + 1) * 100, 1000); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static __init void rb_ipi(void *ignore) |
|
{ |
|
struct rb_test_data *data; |
|
int cpu = smp_processor_id(); |
|
|
|
data = &rb_data[cpu]; |
|
rb_write_something(data, true); |
|
} |
|
|
|
static __init int rb_hammer_test(void *arg) |
|
{ |
|
while (!kthread_should_stop()) { |
|
|
|
/* Send an IPI to all cpus to write data! */ |
|
smp_call_function(rb_ipi, NULL, 1); |
|
/* No sleep, but for non preempt, let others run */ |
|
schedule(); |
|
} |
|
|
|
return 0; |
|
} |
|
|
|
static __init int test_ringbuffer(void) |
|
{ |
|
struct task_struct *rb_hammer; |
|
struct trace_buffer *buffer; |
|
int cpu; |
|
int ret = 0; |
|
|
|
if (security_locked_down(LOCKDOWN_TRACEFS)) { |
|
pr_warn("Lockdown is enabled, skipping ring buffer tests\n"); |
|
return 0; |
|
} |
|
|
|
pr_info("Running ring buffer tests...\n"); |
|
|
|
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); |
|
if (WARN_ON(!buffer)) |
|
return 0; |
|
|
|
/* Disable buffer so that threads can't write to it yet */ |
|
ring_buffer_record_off(buffer); |
|
|
|
for_each_online_cpu(cpu) { |
|
rb_data[cpu].buffer = buffer; |
|
rb_data[cpu].cpu = cpu; |
|
rb_data[cpu].cnt = cpu; |
|
rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu], |
|
"rbtester/%d", cpu); |
|
if (WARN_ON(IS_ERR(rb_threads[cpu]))) { |
|
pr_cont("FAILED\n"); |
|
ret = PTR_ERR(rb_threads[cpu]); |
|
goto out_free; |
|
} |
|
|
|
kthread_bind(rb_threads[cpu], cpu); |
|
wake_up_process(rb_threads[cpu]); |
|
} |
|
|
|
/* Now create the rb hammer! */ |
|
rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); |
|
if (WARN_ON(IS_ERR(rb_hammer))) { |
|
pr_cont("FAILED\n"); |
|
ret = PTR_ERR(rb_hammer); |
|
goto out_free; |
|
} |
|
|
|
ring_buffer_record_on(buffer); |
|
/* |
|
* Show buffer is enabled before setting rb_test_started. |
|
* Yes there's a small race window where events could be |
|
* dropped and the thread wont catch it. But when a ring |
|
* buffer gets enabled, there will always be some kind of |
|
* delay before other CPUs see it. Thus, we don't care about |
|
* those dropped events. We care about events dropped after |
|
* the threads see that the buffer is active. |
|
*/ |
|
smp_wmb(); |
|
rb_test_started = true; |
|
|
|
set_current_state(TASK_INTERRUPTIBLE); |
|
/* Just run for 10 seconds */; |
|
schedule_timeout(10 * HZ); |
|
|
|
kthread_stop(rb_hammer); |
|
|
|
out_free: |
|
for_each_online_cpu(cpu) { |
|
if (!rb_threads[cpu]) |
|
break; |
|
kthread_stop(rb_threads[cpu]); |
|
} |
|
if (ret) { |
|
ring_buffer_free(buffer); |
|
return ret; |
|
} |
|
|
|
/* Report! */ |
|
pr_info("finished\n"); |
|
for_each_online_cpu(cpu) { |
|
struct ring_buffer_event *event; |
|
struct rb_test_data *data = &rb_data[cpu]; |
|
struct rb_item *item; |
|
unsigned long total_events; |
|
unsigned long total_dropped; |
|
unsigned long total_written; |
|
unsigned long total_alloc; |
|
unsigned long total_read = 0; |
|
unsigned long total_size = 0; |
|
unsigned long total_len = 0; |
|
unsigned long total_lost = 0; |
|
unsigned long lost; |
|
int big_event_size; |
|
int small_event_size; |
|
|
|
ret = -1; |
|
|
|
total_events = data->events + data->events_nested; |
|
total_written = data->bytes_written + data->bytes_written_nested; |
|
total_alloc = data->bytes_alloc + data->bytes_alloc_nested; |
|
total_dropped = data->bytes_dropped + data->bytes_dropped_nested; |
|
|
|
big_event_size = data->max_size + data->max_size_nested; |
|
small_event_size = data->min_size + data->min_size_nested; |
|
|
|
pr_info("CPU %d:\n", cpu); |
|
pr_info(" events: %ld\n", total_events); |
|
pr_info(" dropped bytes: %ld\n", total_dropped); |
|
pr_info(" alloced bytes: %ld\n", total_alloc); |
|
pr_info(" written bytes: %ld\n", total_written); |
|
pr_info(" biggest event: %d\n", big_event_size); |
|
pr_info(" smallest event: %d\n", small_event_size); |
|
|
|
if (RB_WARN_ON(buffer, total_dropped)) |
|
break; |
|
|
|
ret = 0; |
|
|
|
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { |
|
total_lost += lost; |
|
item = ring_buffer_event_data(event); |
|
total_len += ring_buffer_event_length(event); |
|
total_size += item->size + sizeof(struct rb_item); |
|
if (memcmp(&item->str[0], rb_string, item->size) != 0) { |
|
pr_info("FAILED!\n"); |
|
pr_info("buffer had: %.*s\n", item->size, item->str); |
|
pr_info("expected: %.*s\n", item->size, rb_string); |
|
RB_WARN_ON(buffer, 1); |
|
ret = -1; |
|
break; |
|
} |
|
total_read++; |
|
} |
|
if (ret) |
|
break; |
|
|
|
ret = -1; |
|
|
|
pr_info(" read events: %ld\n", total_read); |
|
pr_info(" lost events: %ld\n", total_lost); |
|
pr_info(" total events: %ld\n", total_lost + total_read); |
|
pr_info(" recorded len bytes: %ld\n", total_len); |
|
pr_info(" recorded size bytes: %ld\n", total_size); |
|
if (total_lost) |
|
pr_info(" With dropped events, record len and size may not match\n" |
|
" alloced and written from above\n"); |
|
if (!total_lost) { |
|
if (RB_WARN_ON(buffer, total_len != total_alloc || |
|
total_size != total_written)) |
|
break; |
|
} |
|
if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) |
|
break; |
|
|
|
ret = 0; |
|
} |
|
if (!ret) |
|
pr_info("Ring buffer PASSED!\n"); |
|
|
|
ring_buffer_free(buffer); |
|
return 0; |
|
} |
|
|
|
late_initcall(test_ringbuffer); |
|
#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
|
|
|