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674 lines
16 KiB
674 lines
16 KiB
/* SPDX-License-Identifier: GPL-2.0-or-later */ |
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/* |
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* Definitions for the 'struct ptr_ring' datastructure. |
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* |
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* Author: |
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* Michael S. Tsirkin <[email protected]> |
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* |
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* Copyright (C) 2016 Red Hat, Inc. |
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* |
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* This is a limited-size FIFO maintaining pointers in FIFO order, with |
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* one CPU producing entries and another consuming entries from a FIFO. |
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* |
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* This implementation tries to minimize cache-contention when there is a |
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* single producer and a single consumer CPU. |
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*/ |
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|
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#ifndef _LINUX_PTR_RING_H |
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#define _LINUX_PTR_RING_H 1 |
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#ifdef __KERNEL__ |
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#include <linux/spinlock.h> |
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#include <linux/cache.h> |
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#include <linux/types.h> |
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#include <linux/compiler.h> |
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#include <linux/slab.h> |
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#include <linux/mm.h> |
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#include <asm/errno.h> |
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#endif |
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struct ptr_ring { |
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int producer ____cacheline_aligned_in_smp; |
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spinlock_t producer_lock; |
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int consumer_head ____cacheline_aligned_in_smp; /* next valid entry */ |
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int consumer_tail; /* next entry to invalidate */ |
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spinlock_t consumer_lock; |
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/* Shared consumer/producer data */ |
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/* Read-only by both the producer and the consumer */ |
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int size ____cacheline_aligned_in_smp; /* max entries in queue */ |
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int batch; /* number of entries to consume in a batch */ |
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void **queue; |
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}; |
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/* Note: callers invoking this in a loop must use a compiler barrier, |
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* for example cpu_relax(). |
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* |
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* NB: this is unlike __ptr_ring_empty in that callers must hold producer_lock: |
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* see e.g. ptr_ring_full. |
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*/ |
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static inline bool __ptr_ring_full(struct ptr_ring *r) |
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{ |
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return r->queue[r->producer]; |
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} |
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static inline bool ptr_ring_full(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock(&r->producer_lock); |
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ret = __ptr_ring_full(r); |
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spin_unlock(&r->producer_lock); |
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return ret; |
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} |
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static inline bool ptr_ring_full_irq(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock_irq(&r->producer_lock); |
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ret = __ptr_ring_full(r); |
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spin_unlock_irq(&r->producer_lock); |
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return ret; |
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} |
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static inline bool ptr_ring_full_any(struct ptr_ring *r) |
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{ |
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unsigned long flags; |
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bool ret; |
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spin_lock_irqsave(&r->producer_lock, flags); |
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ret = __ptr_ring_full(r); |
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spin_unlock_irqrestore(&r->producer_lock, flags); |
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return ret; |
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} |
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static inline bool ptr_ring_full_bh(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock_bh(&r->producer_lock); |
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ret = __ptr_ring_full(r); |
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spin_unlock_bh(&r->producer_lock); |
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return ret; |
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} |
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/* Note: callers invoking this in a loop must use a compiler barrier, |
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* for example cpu_relax(). Callers must hold producer_lock. |
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* Callers are responsible for making sure pointer that is being queued |
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* points to a valid data. |
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*/ |
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static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr) |
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{ |
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if (unlikely(!r->size) || r->queue[r->producer]) |
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return -ENOSPC; |
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/* Make sure the pointer we are storing points to a valid data. */ |
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/* Pairs with the dependency ordering in __ptr_ring_consume. */ |
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smp_wmb(); |
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WRITE_ONCE(r->queue[r->producer++], ptr); |
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if (unlikely(r->producer >= r->size)) |
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r->producer = 0; |
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return 0; |
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} |
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/* |
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* Note: resize (below) nests producer lock within consumer lock, so if you |
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* consume in interrupt or BH context, you must disable interrupts/BH when |
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* calling this. |
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*/ |
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static inline int ptr_ring_produce(struct ptr_ring *r, void *ptr) |
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{ |
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int ret; |
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spin_lock(&r->producer_lock); |
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ret = __ptr_ring_produce(r, ptr); |
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spin_unlock(&r->producer_lock); |
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return ret; |
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} |
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static inline int ptr_ring_produce_irq(struct ptr_ring *r, void *ptr) |
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{ |
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int ret; |
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spin_lock_irq(&r->producer_lock); |
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ret = __ptr_ring_produce(r, ptr); |
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spin_unlock_irq(&r->producer_lock); |
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return ret; |
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} |
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static inline int ptr_ring_produce_any(struct ptr_ring *r, void *ptr) |
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{ |
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unsigned long flags; |
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int ret; |
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spin_lock_irqsave(&r->producer_lock, flags); |
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ret = __ptr_ring_produce(r, ptr); |
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spin_unlock_irqrestore(&r->producer_lock, flags); |
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return ret; |
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} |
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static inline int ptr_ring_produce_bh(struct ptr_ring *r, void *ptr) |
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{ |
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int ret; |
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spin_lock_bh(&r->producer_lock); |
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ret = __ptr_ring_produce(r, ptr); |
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spin_unlock_bh(&r->producer_lock); |
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return ret; |
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} |
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static inline void *__ptr_ring_peek(struct ptr_ring *r) |
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{ |
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if (likely(r->size)) |
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return READ_ONCE(r->queue[r->consumer_head]); |
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return NULL; |
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} |
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/* |
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* Test ring empty status without taking any locks. |
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* |
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* NB: This is only safe to call if ring is never resized. |
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* |
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* However, if some other CPU consumes ring entries at the same time, the value |
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* returned is not guaranteed to be correct. |
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* |
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* In this case - to avoid incorrectly detecting the ring |
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* as empty - the CPU consuming the ring entries is responsible |
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* for either consuming all ring entries until the ring is empty, |
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* or synchronizing with some other CPU and causing it to |
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* re-test __ptr_ring_empty and/or consume the ring enteries |
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* after the synchronization point. |
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* |
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* Note: callers invoking this in a loop must use a compiler barrier, |
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* for example cpu_relax(). |
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*/ |
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static inline bool __ptr_ring_empty(struct ptr_ring *r) |
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{ |
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if (likely(r->size)) |
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return !r->queue[READ_ONCE(r->consumer_head)]; |
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return true; |
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} |
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static inline bool ptr_ring_empty(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock(&r->consumer_lock); |
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ret = __ptr_ring_empty(r); |
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spin_unlock(&r->consumer_lock); |
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return ret; |
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} |
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static inline bool ptr_ring_empty_irq(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock_irq(&r->consumer_lock); |
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ret = __ptr_ring_empty(r); |
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spin_unlock_irq(&r->consumer_lock); |
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return ret; |
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} |
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static inline bool ptr_ring_empty_any(struct ptr_ring *r) |
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{ |
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unsigned long flags; |
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bool ret; |
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spin_lock_irqsave(&r->consumer_lock, flags); |
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ret = __ptr_ring_empty(r); |
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spin_unlock_irqrestore(&r->consumer_lock, flags); |
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return ret; |
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} |
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static inline bool ptr_ring_empty_bh(struct ptr_ring *r) |
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{ |
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bool ret; |
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spin_lock_bh(&r->consumer_lock); |
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ret = __ptr_ring_empty(r); |
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spin_unlock_bh(&r->consumer_lock); |
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return ret; |
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} |
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/* Must only be called after __ptr_ring_peek returned !NULL */ |
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static inline void __ptr_ring_discard_one(struct ptr_ring *r) |
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{ |
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/* Fundamentally, what we want to do is update consumer |
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* index and zero out the entry so producer can reuse it. |
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* Doing it naively at each consume would be as simple as: |
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* consumer = r->consumer; |
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* r->queue[consumer++] = NULL; |
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* if (unlikely(consumer >= r->size)) |
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* consumer = 0; |
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* r->consumer = consumer; |
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* but that is suboptimal when the ring is full as producer is writing |
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* out new entries in the same cache line. Defer these updates until a |
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* batch of entries has been consumed. |
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*/ |
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/* Note: we must keep consumer_head valid at all times for __ptr_ring_empty |
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* to work correctly. |
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*/ |
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int consumer_head = r->consumer_head; |
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int head = consumer_head++; |
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/* Once we have processed enough entries invalidate them in |
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* the ring all at once so producer can reuse their space in the ring. |
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* We also do this when we reach end of the ring - not mandatory |
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* but helps keep the implementation simple. |
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*/ |
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if (unlikely(consumer_head - r->consumer_tail >= r->batch || |
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consumer_head >= r->size)) { |
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/* Zero out entries in the reverse order: this way we touch the |
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* cache line that producer might currently be reading the last; |
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* producer won't make progress and touch other cache lines |
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* besides the first one until we write out all entries. |
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*/ |
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while (likely(head >= r->consumer_tail)) |
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r->queue[head--] = NULL; |
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r->consumer_tail = consumer_head; |
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} |
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if (unlikely(consumer_head >= r->size)) { |
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consumer_head = 0; |
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r->consumer_tail = 0; |
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} |
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/* matching READ_ONCE in __ptr_ring_empty for lockless tests */ |
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WRITE_ONCE(r->consumer_head, consumer_head); |
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} |
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static inline void *__ptr_ring_consume(struct ptr_ring *r) |
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{ |
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void *ptr; |
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/* The READ_ONCE in __ptr_ring_peek guarantees that anyone |
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* accessing data through the pointer is up to date. Pairs |
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* with smp_wmb in __ptr_ring_produce. |
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*/ |
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ptr = __ptr_ring_peek(r); |
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if (ptr) |
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__ptr_ring_discard_one(r); |
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return ptr; |
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} |
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static inline int __ptr_ring_consume_batched(struct ptr_ring *r, |
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void **array, int n) |
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{ |
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void *ptr; |
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int i; |
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for (i = 0; i < n; i++) { |
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ptr = __ptr_ring_consume(r); |
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if (!ptr) |
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break; |
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array[i] = ptr; |
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} |
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return i; |
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} |
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/* |
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* Note: resize (below) nests producer lock within consumer lock, so if you |
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* call this in interrupt or BH context, you must disable interrupts/BH when |
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* producing. |
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*/ |
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static inline void *ptr_ring_consume(struct ptr_ring *r) |
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{ |
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void *ptr; |
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spin_lock(&r->consumer_lock); |
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ptr = __ptr_ring_consume(r); |
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spin_unlock(&r->consumer_lock); |
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return ptr; |
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} |
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static inline void *ptr_ring_consume_irq(struct ptr_ring *r) |
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{ |
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void *ptr; |
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spin_lock_irq(&r->consumer_lock); |
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ptr = __ptr_ring_consume(r); |
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spin_unlock_irq(&r->consumer_lock); |
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return ptr; |
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} |
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static inline void *ptr_ring_consume_any(struct ptr_ring *r) |
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{ |
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unsigned long flags; |
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void *ptr; |
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spin_lock_irqsave(&r->consumer_lock, flags); |
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ptr = __ptr_ring_consume(r); |
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spin_unlock_irqrestore(&r->consumer_lock, flags); |
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return ptr; |
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} |
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static inline void *ptr_ring_consume_bh(struct ptr_ring *r) |
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{ |
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void *ptr; |
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spin_lock_bh(&r->consumer_lock); |
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ptr = __ptr_ring_consume(r); |
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spin_unlock_bh(&r->consumer_lock); |
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return ptr; |
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} |
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static inline int ptr_ring_consume_batched(struct ptr_ring *r, |
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void **array, int n) |
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{ |
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int ret; |
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spin_lock(&r->consumer_lock); |
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ret = __ptr_ring_consume_batched(r, array, n); |
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spin_unlock(&r->consumer_lock); |
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return ret; |
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} |
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static inline int ptr_ring_consume_batched_irq(struct ptr_ring *r, |
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void **array, int n) |
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{ |
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int ret; |
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spin_lock_irq(&r->consumer_lock); |
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ret = __ptr_ring_consume_batched(r, array, n); |
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spin_unlock_irq(&r->consumer_lock); |
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return ret; |
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} |
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static inline int ptr_ring_consume_batched_any(struct ptr_ring *r, |
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void **array, int n) |
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{ |
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unsigned long flags; |
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int ret; |
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spin_lock_irqsave(&r->consumer_lock, flags); |
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ret = __ptr_ring_consume_batched(r, array, n); |
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spin_unlock_irqrestore(&r->consumer_lock, flags); |
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return ret; |
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} |
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static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r, |
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void **array, int n) |
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{ |
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int ret; |
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spin_lock_bh(&r->consumer_lock); |
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ret = __ptr_ring_consume_batched(r, array, n); |
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spin_unlock_bh(&r->consumer_lock); |
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return ret; |
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} |
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/* Cast to structure type and call a function without discarding from FIFO. |
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* Function must return a value. |
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* Callers must take consumer_lock. |
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*/ |
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#define __PTR_RING_PEEK_CALL(r, f) ((f)(__ptr_ring_peek(r))) |
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#define PTR_RING_PEEK_CALL(r, f) ({ \ |
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typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \ |
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\ |
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spin_lock(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \ |
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spin_unlock(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v; \ |
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}) |
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#define PTR_RING_PEEK_CALL_IRQ(r, f) ({ \ |
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typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \ |
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\ |
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spin_lock_irq(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \ |
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spin_unlock_irq(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v; \ |
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}) |
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#define PTR_RING_PEEK_CALL_BH(r, f) ({ \ |
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typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \ |
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\ |
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spin_lock_bh(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \ |
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spin_unlock_bh(&(r)->consumer_lock); \ |
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__PTR_RING_PEEK_CALL_v; \ |
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}) |
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#define PTR_RING_PEEK_CALL_ANY(r, f) ({ \ |
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typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \ |
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unsigned long __PTR_RING_PEEK_CALL_f;\ |
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\ |
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spin_lock_irqsave(&(r)->consumer_lock, __PTR_RING_PEEK_CALL_f); \ |
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__PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \ |
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spin_unlock_irqrestore(&(r)->consumer_lock, __PTR_RING_PEEK_CALL_f); \ |
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__PTR_RING_PEEK_CALL_v; \ |
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}) |
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/* Not all gfp_t flags (besides GFP_KERNEL) are allowed. See |
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* documentation for vmalloc for which of them are legal. |
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*/ |
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static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp) |
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{ |
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if (size > KMALLOC_MAX_SIZE / sizeof(void *)) |
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return NULL; |
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return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO); |
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} |
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static inline void __ptr_ring_set_size(struct ptr_ring *r, int size) |
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{ |
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r->size = size; |
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r->batch = SMP_CACHE_BYTES * 2 / sizeof(*(r->queue)); |
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/* We need to set batch at least to 1 to make logic |
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* in __ptr_ring_discard_one work correctly. |
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* Batching too much (because ring is small) would cause a lot of |
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* burstiness. Needs tuning, for now disable batching. |
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*/ |
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if (r->batch > r->size / 2 || !r->batch) |
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r->batch = 1; |
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} |
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static inline int ptr_ring_init(struct ptr_ring *r, int size, gfp_t gfp) |
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{ |
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r->queue = __ptr_ring_init_queue_alloc(size, gfp); |
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if (!r->queue) |
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return -ENOMEM; |
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__ptr_ring_set_size(r, size); |
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r->producer = r->consumer_head = r->consumer_tail = 0; |
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spin_lock_init(&r->producer_lock); |
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spin_lock_init(&r->consumer_lock); |
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return 0; |
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} |
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/* |
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* Return entries into ring. Destroy entries that don't fit. |
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* |
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* Note: this is expected to be a rare slow path operation. |
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* |
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* Note: producer lock is nested within consumer lock, so if you |
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* resize you must make sure all uses nest correctly. |
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* In particular if you consume ring in interrupt or BH context, you must |
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* disable interrupts/BH when doing so. |
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*/ |
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static inline void ptr_ring_unconsume(struct ptr_ring *r, void **batch, int n, |
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void (*destroy)(void *)) |
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{ |
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unsigned long flags; |
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int head; |
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spin_lock_irqsave(&r->consumer_lock, flags); |
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spin_lock(&r->producer_lock); |
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if (!r->size) |
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goto done; |
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/* |
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* Clean out buffered entries (for simplicity). This way following code |
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* can test entries for NULL and if not assume they are valid. |
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*/ |
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head = r->consumer_head - 1; |
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while (likely(head >= r->consumer_tail)) |
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r->queue[head--] = NULL; |
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r->consumer_tail = r->consumer_head; |
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/* |
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* Go over entries in batch, start moving head back and copy entries. |
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* Stop when we run into previously unconsumed entries. |
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*/ |
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while (n) { |
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head = r->consumer_head - 1; |
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if (head < 0) |
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head = r->size - 1; |
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if (r->queue[head]) { |
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/* This batch entry will have to be destroyed. */ |
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goto done; |
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} |
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r->queue[head] = batch[--n]; |
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r->consumer_tail = head; |
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/* matching READ_ONCE in __ptr_ring_empty for lockless tests */ |
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WRITE_ONCE(r->consumer_head, head); |
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} |
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done: |
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/* Destroy all entries left in the batch. */ |
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while (n) |
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destroy(batch[--n]); |
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spin_unlock(&r->producer_lock); |
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spin_unlock_irqrestore(&r->consumer_lock, flags); |
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} |
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static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue, |
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int size, gfp_t gfp, |
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void (*destroy)(void *)) |
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{ |
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int producer = 0; |
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void **old; |
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void *ptr; |
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while ((ptr = __ptr_ring_consume(r))) |
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if (producer < size) |
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queue[producer++] = ptr; |
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else if (destroy) |
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destroy(ptr); |
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if (producer >= size) |
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producer = 0; |
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__ptr_ring_set_size(r, size); |
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r->producer = producer; |
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r->consumer_head = 0; |
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r->consumer_tail = 0; |
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old = r->queue; |
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r->queue = queue; |
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return old; |
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} |
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|
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/* |
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* Note: producer lock is nested within consumer lock, so if you |
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* resize you must make sure all uses nest correctly. |
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* In particular if you consume ring in interrupt or BH context, you must |
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* disable interrupts/BH when doing so. |
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*/ |
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static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp, |
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void (*destroy)(void *)) |
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{ |
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unsigned long flags; |
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void **queue = __ptr_ring_init_queue_alloc(size, gfp); |
|
void **old; |
|
|
|
if (!queue) |
|
return -ENOMEM; |
|
|
|
spin_lock_irqsave(&(r)->consumer_lock, flags); |
|
spin_lock(&(r)->producer_lock); |
|
|
|
old = __ptr_ring_swap_queue(r, queue, size, gfp, destroy); |
|
|
|
spin_unlock(&(r)->producer_lock); |
|
spin_unlock_irqrestore(&(r)->consumer_lock, flags); |
|
|
|
kvfree(old); |
|
|
|
return 0; |
|
} |
|
|
|
/* |
|
* Note: producer lock is nested within consumer lock, so if you |
|
* resize you must make sure all uses nest correctly. |
|
* In particular if you consume ring in interrupt or BH context, you must |
|
* disable interrupts/BH when doing so. |
|
*/ |
|
static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, |
|
unsigned int nrings, |
|
int size, |
|
gfp_t gfp, void (*destroy)(void *)) |
|
{ |
|
unsigned long flags; |
|
void ***queues; |
|
int i; |
|
|
|
queues = kmalloc_array(nrings, sizeof(*queues), gfp); |
|
if (!queues) |
|
goto noqueues; |
|
|
|
for (i = 0; i < nrings; ++i) { |
|
queues[i] = __ptr_ring_init_queue_alloc(size, gfp); |
|
if (!queues[i]) |
|
goto nomem; |
|
} |
|
|
|
for (i = 0; i < nrings; ++i) { |
|
spin_lock_irqsave(&(rings[i])->consumer_lock, flags); |
|
spin_lock(&(rings[i])->producer_lock); |
|
queues[i] = __ptr_ring_swap_queue(rings[i], queues[i], |
|
size, gfp, destroy); |
|
spin_unlock(&(rings[i])->producer_lock); |
|
spin_unlock_irqrestore(&(rings[i])->consumer_lock, flags); |
|
} |
|
|
|
for (i = 0; i < nrings; ++i) |
|
kvfree(queues[i]); |
|
|
|
kfree(queues); |
|
|
|
return 0; |
|
|
|
nomem: |
|
while (--i >= 0) |
|
kvfree(queues[i]); |
|
|
|
kfree(queues); |
|
|
|
noqueues: |
|
return -ENOMEM; |
|
} |
|
|
|
static inline void ptr_ring_cleanup(struct ptr_ring *r, void (*destroy)(void *)) |
|
{ |
|
void *ptr; |
|
|
|
if (destroy) |
|
while ((ptr = ptr_ring_consume(r))) |
|
destroy(ptr); |
|
kvfree(r->queue); |
|
} |
|
|
|
#endif /* _LINUX_PTR_RING_H */
|
|
|