1 files changed, 448 insertions, 0 deletions
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
new file mode 100644
index 000000000000..2052011bf9fb
--- /dev/null
+++ b/include/linux/ptr_ring.h
@@ -0,0 +1,448 @@
+/*
+ *	Definitions for the 'struct ptr_ring' datastructure.
+ *
+ *	Author:
+ *		Michael S. Tsirkin <mst@redhat.com>
+ *
+ *	Copyright (C) 2016 Red Hat, Inc.
+ *
+ *	This program is free software; you can redistribute it and/or modify it
+ *	under the terms of the GNU General Public License as published by the
+ *	Free Software Foundation; either version 2 of the License, or (at your
+ *	option) any later version.
+ *
+ *	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/cache.h>
+#include <linux/slab.h>
+#include <asm/errno.h>
+#endif
+
+struct ptr_ring {
+	int producer ____cacheline_aligned_in_smp;
+	spinlock_t producer_lock;
+	int consumer ____cacheline_aligned_in_smp;
+	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 */
+	void **queue;
+};
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax().  If ring is ever resized, callers must hold
+ * producer_lock - see e.g. ptr_ring_full.  Otherwise, if callers don't hold
+ * producer_lock, the next call to __ptr_ring_produce may fail.
+ */
+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.
+ */
+static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
+{
+	if (unlikely(!r->size) || r->queue[r->producer])
+		return -ENOSPC;
+
+	r->queue[r->producer++] = ptr;
+	if (unlikely(r->producer >= r->size))
+		r->producer = 0;
+	return 0;
+}
+
+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;
+}
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax(). Callers must take consumer_lock
+ * if they dereference the pointer - see e.g. PTR_RING_PEEK_CALL.
+ * If ring is never resized, and if the pointer is merely
+ * tested, there's no need to take the lock - see e.g.  __ptr_ring_empty.
+ */
+static inline void *__ptr_ring_peek(struct ptr_ring *r)
+{
+	if (likely(r->size))
+		return r->queue[r->consumer];
+	return NULL;
+}
+
+/* Note: callers invoking this in a loop must use a compiler barrier,
+ * for example cpu_relax(). Callers must take consumer_lock
+ * if the ring is ever resized - see e.g. ptr_ring_empty.
+ */
+static inline bool __ptr_ring_empty(struct ptr_ring *r)
+{
+	return !__ptr_ring_peek(r);
+}
+
+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)
+{
+	r->queue[r->consumer++] = NULL;
+	if (unlikely(r->consumer >= r->size))
+		r->consumer = 0;
+}
+
+static inline void *__ptr_ring_consume(struct ptr_ring *r)
+{
+	void *ptr;
+
+	ptr = __ptr_ring_peek(r);
+	if (ptr)
+		__ptr_ring_discard_one(r);
+
+	return ptr;
+}
+
+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;
+}
+
+/* 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; \
+})
+
+static inline void **__ptr_ring_init_queue_alloc(int size, gfp_t gfp)
+{
+	return kzalloc(ALIGN(size * sizeof(void *), SMP_CACHE_BYTES), gfp);
+}
+
+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;
+
+	r->size = size;
+	r->producer = r->consumer = 0;
+	spin_lock_init(&r->producer_lock);
+	spin_lock_init(&r->consumer_lock);
+
+	return 0;
+}
+
+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);
+
+	r->size = size;
+	r->producer = producer;
+	r->consumer = 0;
+	old = r->queue;
+	r->queue = queue;
+
+	return old;
+}
+
+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)->producer_lock, flags);
+
+	old = __ptr_ring_swap_queue(r, queue, size, gfp, destroy);
+
+	spin_unlock_irqrestore(&(r)->producer_lock, flags);
+
+	kfree(old);
+
+	return 0;
+}
+
+static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, int nrings,
+					   int size,
+					   gfp_t gfp, void (*destroy)(void *))
+{
+	unsigned long flags;
+	void ***queues;
+	int i;
+
+	queues = kmalloc(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])->producer_lock, flags);
+		queues[i] = __ptr_ring_swap_queue(rings[i], queues[i],
+						  size, gfp, destroy);
+		spin_unlock_irqrestore(&(rings[i])->producer_lock, flags);
+	}
+
+	for (i = 0; i < nrings; ++i)
+		kfree(queues[i]);
+
+	kfree(queues);
+
+	return 0;
+
+nomem:
+	while (--i >= 0)
+		kfree(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);
+	kfree(r->queue);
+}
+
+#endif /* _LINUX_PTR_RING_H  */