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