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287 lines
8.5 KiB
287 lines
8.5 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* linux/include/linux/relay.h |
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* |
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* Copyright (C) 2002, 2003 - Tom Zanussi ([email protected]), IBM Corp |
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* Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour ([email protected]) |
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* |
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* CONFIG_RELAY definitions and declarations |
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*/ |
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#ifndef _LINUX_RELAY_H |
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#define _LINUX_RELAY_H |
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#include <linux/types.h> |
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#include <linux/sched.h> |
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#include <linux/timer.h> |
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#include <linux/wait.h> |
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#include <linux/list.h> |
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#include <linux/irq_work.h> |
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#include <linux/bug.h> |
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#include <linux/fs.h> |
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#include <linux/poll.h> |
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#include <linux/kref.h> |
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#include <linux/percpu.h> |
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/* |
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* Tracks changes to rchan/rchan_buf structs |
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*/ |
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#define RELAYFS_CHANNEL_VERSION 7 |
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/* |
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* Per-cpu relay channel buffer |
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*/ |
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struct rchan_buf |
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{ |
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void *start; /* start of channel buffer */ |
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void *data; /* start of current sub-buffer */ |
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size_t offset; /* current offset into sub-buffer */ |
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size_t subbufs_produced; /* count of sub-buffers produced */ |
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size_t subbufs_consumed; /* count of sub-buffers consumed */ |
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struct rchan *chan; /* associated channel */ |
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wait_queue_head_t read_wait; /* reader wait queue */ |
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struct irq_work wakeup_work; /* reader wakeup */ |
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struct dentry *dentry; /* channel file dentry */ |
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struct kref kref; /* channel buffer refcount */ |
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struct page **page_array; /* array of current buffer pages */ |
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unsigned int page_count; /* number of current buffer pages */ |
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unsigned int finalized; /* buffer has been finalized */ |
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size_t *padding; /* padding counts per sub-buffer */ |
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size_t prev_padding; /* temporary variable */ |
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size_t bytes_consumed; /* bytes consumed in cur read subbuf */ |
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size_t early_bytes; /* bytes consumed before VFS inited */ |
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unsigned int cpu; /* this buf's cpu */ |
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} ____cacheline_aligned; |
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/* |
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* Relay channel data structure |
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*/ |
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struct rchan |
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{ |
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u32 version; /* the version of this struct */ |
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size_t subbuf_size; /* sub-buffer size */ |
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size_t n_subbufs; /* number of sub-buffers per buffer */ |
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size_t alloc_size; /* total buffer size allocated */ |
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const struct rchan_callbacks *cb; /* client callbacks */ |
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struct kref kref; /* channel refcount */ |
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void *private_data; /* for user-defined data */ |
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size_t last_toobig; /* tried to log event > subbuf size */ |
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struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */ |
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int is_global; /* One global buffer ? */ |
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struct list_head list; /* for channel list */ |
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struct dentry *parent; /* parent dentry passed to open */ |
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int has_base_filename; /* has a filename associated? */ |
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char base_filename[NAME_MAX]; /* saved base filename */ |
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}; |
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/* |
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* Relay channel client callbacks |
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*/ |
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struct rchan_callbacks |
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{ |
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/* |
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* subbuf_start - called on buffer-switch to a new sub-buffer |
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* @buf: the channel buffer containing the new sub-buffer |
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* @subbuf: the start of the new sub-buffer |
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* @prev_subbuf: the start of the previous sub-buffer |
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* @prev_padding: unused space at the end of previous sub-buffer |
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* |
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* The client should return 1 to continue logging, 0 to stop |
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* logging. |
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* |
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* This callback is optional. |
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* |
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* NOTE: subbuf_start will also be invoked when the buffer is |
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* created, so that the first sub-buffer can be initialized |
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* if necessary. In this case, prev_subbuf will be NULL. |
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* |
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* NOTE: the client can reserve bytes at the beginning of the new |
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* sub-buffer by calling subbuf_start_reserve() in this callback. |
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*/ |
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int (*subbuf_start) (struct rchan_buf *buf, |
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void *subbuf, |
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void *prev_subbuf, |
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size_t prev_padding); |
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/* |
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* create_buf_file - create file to represent a relay channel buffer |
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* @filename: the name of the file to create |
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* @parent: the parent of the file to create |
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* @mode: the mode of the file to create |
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* @buf: the channel buffer |
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* @is_global: outparam - set non-zero if the buffer should be global |
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* |
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* Called during relay_open(), once for each per-cpu buffer, |
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* to allow the client to create a file to be used to |
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* represent the corresponding channel buffer. If the file is |
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* created outside of relay, the parent must also exist in |
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* that filesystem. |
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* |
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* The callback should return the dentry of the file created |
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* to represent the relay buffer. |
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* |
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* Setting the is_global outparam to a non-zero value will |
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* cause relay_open() to create a single global buffer rather |
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* than the default set of per-cpu buffers. |
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* |
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* This callback is mandatory. |
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* |
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* See Documentation/filesystems/relay.rst for more info. |
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*/ |
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struct dentry *(*create_buf_file)(const char *filename, |
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struct dentry *parent, |
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umode_t mode, |
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struct rchan_buf *buf, |
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int *is_global); |
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/* |
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* remove_buf_file - remove file representing a relay channel buffer |
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* @dentry: the dentry of the file to remove |
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* |
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* Called during relay_close(), once for each per-cpu buffer, |
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* to allow the client to remove a file used to represent a |
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* channel buffer. |
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* |
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* The callback should return 0 if successful, negative if not. |
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* |
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* This callback is mandatory. |
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*/ |
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int (*remove_buf_file)(struct dentry *dentry); |
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}; |
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/* |
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* CONFIG_RELAY kernel API, kernel/relay.c |
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*/ |
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struct rchan *relay_open(const char *base_filename, |
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struct dentry *parent, |
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size_t subbuf_size, |
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size_t n_subbufs, |
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const struct rchan_callbacks *cb, |
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void *private_data); |
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extern int relay_late_setup_files(struct rchan *chan, |
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const char *base_filename, |
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struct dentry *parent); |
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extern void relay_close(struct rchan *chan); |
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extern void relay_flush(struct rchan *chan); |
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extern void relay_subbufs_consumed(struct rchan *chan, |
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unsigned int cpu, |
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size_t consumed); |
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extern void relay_reset(struct rchan *chan); |
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extern int relay_buf_full(struct rchan_buf *buf); |
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extern size_t relay_switch_subbuf(struct rchan_buf *buf, |
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size_t length); |
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/** |
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* relay_write - write data into the channel |
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* @chan: relay channel |
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* @data: data to be written |
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* @length: number of bytes to write |
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* |
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* Writes data into the current cpu's channel buffer. |
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* |
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* Protects the buffer by disabling interrupts. Use this |
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* if you might be logging from interrupt context. Try |
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* __relay_write() if you know you won't be logging from |
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* interrupt context. |
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*/ |
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static inline void relay_write(struct rchan *chan, |
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const void *data, |
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size_t length) |
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{ |
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unsigned long flags; |
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struct rchan_buf *buf; |
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local_irq_save(flags); |
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buf = *this_cpu_ptr(chan->buf); |
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if (unlikely(buf->offset + length > chan->subbuf_size)) |
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length = relay_switch_subbuf(buf, length); |
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memcpy(buf->data + buf->offset, data, length); |
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buf->offset += length; |
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local_irq_restore(flags); |
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} |
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/** |
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* __relay_write - write data into the channel |
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* @chan: relay channel |
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* @data: data to be written |
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* @length: number of bytes to write |
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* |
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* Writes data into the current cpu's channel buffer. |
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* |
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* Protects the buffer by disabling preemption. Use |
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* relay_write() if you might be logging from interrupt |
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* context. |
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*/ |
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static inline void __relay_write(struct rchan *chan, |
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const void *data, |
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size_t length) |
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{ |
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struct rchan_buf *buf; |
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buf = *get_cpu_ptr(chan->buf); |
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if (unlikely(buf->offset + length > buf->chan->subbuf_size)) |
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length = relay_switch_subbuf(buf, length); |
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memcpy(buf->data + buf->offset, data, length); |
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buf->offset += length; |
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put_cpu_ptr(chan->buf); |
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} |
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/** |
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* relay_reserve - reserve slot in channel buffer |
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* @chan: relay channel |
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* @length: number of bytes to reserve |
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* |
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* Returns pointer to reserved slot, NULL if full. |
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* |
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* Reserves a slot in the current cpu's channel buffer. |
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* Does not protect the buffer at all - caller must provide |
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* appropriate synchronization. |
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*/ |
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static inline void *relay_reserve(struct rchan *chan, size_t length) |
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{ |
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void *reserved = NULL; |
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struct rchan_buf *buf = *get_cpu_ptr(chan->buf); |
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if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { |
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length = relay_switch_subbuf(buf, length); |
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if (!length) |
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goto end; |
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} |
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reserved = buf->data + buf->offset; |
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buf->offset += length; |
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end: |
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put_cpu_ptr(chan->buf); |
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return reserved; |
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} |
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/** |
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* subbuf_start_reserve - reserve bytes at the start of a sub-buffer |
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* @buf: relay channel buffer |
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* @length: number of bytes to reserve |
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* |
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* Helper function used to reserve bytes at the beginning of |
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* a sub-buffer in the subbuf_start() callback. |
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*/ |
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static inline void subbuf_start_reserve(struct rchan_buf *buf, |
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size_t length) |
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{ |
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BUG_ON(length >= buf->chan->subbuf_size - 1); |
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buf->offset = length; |
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} |
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/* |
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* exported relay file operations, kernel/relay.c |
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*/ |
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extern const struct file_operations relay_file_operations; |
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#ifdef CONFIG_RELAY |
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int relay_prepare_cpu(unsigned int cpu); |
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#else |
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#define relay_prepare_cpu NULL |
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#endif |
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#endif /* _LINUX_RELAY_H */ |
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