/*
* 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().
* Callers don't need to take producer lock - if they don't
* 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)
{
barrier();
return __ptr_ring_full(r);
}
/* Note: callers invoking this in a loop must use a compiler barrier,
* for example cpu_relax().
*/
static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
{
if (__ptr_ring_full(r))
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.
* There's no need for a lock if pointer is merely tested - see e.g.
* ptr_ring_empty.
*/
static inline void *__ptr_ring_peek(struct ptr_ring *r)
{
return r->queue[r->consumer];
}
static inline bool ptr_ring_empty(struct ptr_ring *r)
{
barrier();
return !__ptr_ring_peek(r);
}
/* 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 int ptr_ring_init(struct ptr_ring *r, int size, gfp_t gfp)
{
r->queue = kzalloc(ALIGN(size * sizeof *(r->queue), SMP_CACHE_BYTES),
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_cleanup(struct ptr_ring *r)
{
kfree(r->queue);
}
#endif /* _LINUX_PTR_RING_H */
