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/* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2010-2017 Intel Corporation
* Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
* All rights reserved.
* Derived from FreeBSD's bufring.h
* Used as BSD-3 Licensed with permission from Kip Macy.
*/
#ifndef _RTE_RING_GENERIC_H_
#define _RTE_RING_GENERIC_H_
static __rte_always_inline void
update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
uint32_t single, uint32_t enqueue)
{
if (enqueue)
rte_smp_wmb();
else
rte_smp_rmb();
/*
* If there are other enqueues/dequeues in progress that preceded us,
* we need to wait for them to complete
*/
if (!single)
while (unlikely(ht->tail != old_val))
rte_pause();
ht->tail = new_val;
}
/**
* @internal This function updates the producer head for enqueue
*
* @param r
* A pointer to the ring structure
* @param is_sp
* Indicates whether multi-producer path is needed or not
* @param n
* The number of elements we will want to enqueue, i.e. how far should the
* head be moved
* @param behavior
* RTE_RING_QUEUE_FIXED: Enqueue a fixed number of items from a ring
* RTE_RING_QUEUE_VARIABLE: Enqueue as many items as possible from ring
* @param old_head
* Returns head value as it was before the move, i.e. where enqueue starts
* @param new_head
* Returns the current/new head value i.e. where enqueue finishes
* @param free_entries
* Returns the amount of free space in the ring BEFORE head was moved
* @return
* Actual number of objects enqueued.
* If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only.
*/
static __rte_always_inline unsigned int
__rte_ring_move_prod_head(struct rte_ring *r, unsigned int is_sp,
unsigned int n, enum rte_ring_queue_behavior behavior,
uint32_t *old_head, uint32_t *new_head,
uint32_t *free_entries)
{
const uint32_t capacity = r->capacity;
unsigned int max = n;
int success;
do {
/* Reset n to the initial burst count */
n = max;
*old_head = r->prod.head;
/* add rmb barrier to avoid load/load reorder in weak
* memory model. It is noop on x86
*/
rte_smp_rmb();
/*
* The subtraction is done between two unsigned 32bits value
* (the result is always modulo 32 bits even if we have
* *old_head > cons_tail). So 'free_entries' is always between 0
* and capacity (which is < size).
*/
*free_entries = (capacity + r->cons.tail - *old_head);
/* check that we have enough room in ring */
if (unlikely(n > *free_entries))
n = (behavior == RTE_RING_QUEUE_FIXED) ?
0 : *free_entries;
if (n == 0)
return 0;
*new_head = *old_head + n;
if (is_sp)
r->prod.head = *new_head, success = 1;
else
success = rte_atomic32_cmpset(&r->prod.head,
*old_head, *new_head);
} while (unlikely(success == 0));
return n;
}
/**
* @internal This function updates the consumer head for dequeue
*
* @param r
* A pointer to the ring structure
* @param is_sc
* Indicates whether multi-consumer path is needed or not
* @param n
* The number of elements we will want to enqueue, i.e. how far should the
* head be moved
* @param behavior
* RTE_RING_QUEUE_FIXED: Dequeue a fixed number of items from a ring
* RTE_RING_QUEUE_VARIABLE: Dequeue as many items as possible from ring
* @param old_head
* Returns head value as it was before the move, i.e. where dequeue starts
* @param new_head
* Returns the current/new head value i.e. where dequeue finishes
* @param entries
* Returns the number of entries in the ring BEFORE head was moved
* @return
* - Actual number of objects dequeued.
* If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only.
*/
static __rte_always_inline unsigned int
__rte_ring_move_cons_head(struct rte_ring *r, unsigned int is_sc,
unsigned int n, enum rte_ring_queue_behavior behavior,
uint32_t *old_head, uint32_t *new_head,
uint32_t *entries)
{
unsigned int max = n;
int success;
/* move cons.head atomically */
do {
/* Restore n as it may change every loop */
n = max;
*old_head = r->cons.head;
/* add rmb barrier to avoid load/load reorder in weak
* memory model. It is noop on x86
*/
rte_smp_rmb();
/* The subtraction is done between two unsigned 32bits value
* (the result is always modulo 32 bits even if we have
* cons_head > prod_tail). So 'entries' is always between 0
* and size(ring)-1.
*/
*entries = (r->prod.tail - *old_head);
/* Set the actual entries for dequeue */
if (n > *entries)
n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries;
if (unlikely(n == 0))
return 0;
*new_head = *old_head + n;
if (is_sc)
r->cons.head = *new_head, success = 1;
else
success = rte_atomic32_cmpset(&r->cons.head, *old_head,
*new_head);
} while (unlikely(success == 0));
return n;
}
#endif /* _RTE_RING_GENERIC_H_ */
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