+// SPDX-FileCopyrightText: 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+// SPDX-FileCopyrightText: 2011-2012 Lai Jiangshan <laijs@cn.fujitsu.com>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
#ifndef _URCU_WFCQUEUE_STATIC_H
#define _URCU_WFCQUEUE_STATIC_H
/*
- * urcu/static/wfcqueue.h
- *
* Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
*
* TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfcqueue.h for
* linking dynamically with the userspace rcu library.
- *
- * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <pthread.h>
-#include <assert.h>
#include <poll.h>
#include <stdbool.h>
+#include <urcu/assert.h>
#include <urcu/compiler.h>
#include <urcu/uatomic.h>
node->next = NULL;
}
+static inline void _cds_wfcq_node_init_atomic(struct cds_wfcq_node *node)
+{
+ uatomic_store(&node->next, NULL, CMM_RELAXED);
+}
+
/*
* cds_wfcq_init: initialize wait-free queue (with lock). Pair with
* cds_wfcq_destroy().
_cds_wfcq_node_init(&head->node);
tail->p = &head->node;
ret = pthread_mutex_init(&head->lock, NULL);
- assert(!ret);
+ urcu_posix_assert(!ret);
}
/*
* cds_wfcq_init().
*/
static inline void _cds_wfcq_destroy(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
+ struct cds_wfcq_tail *tail __attribute__((unused)))
{
int ret = pthread_mutex_destroy(&head->lock);
- assert(!ret);
+ urcu_posix_assert(!ret);
}
/*
* common case to ensure that dequeuers do not frequently access
* enqueuer's tail->p cache line.
*/
- return CMM_LOAD_SHARED(head->node.next) == NULL
- && CMM_LOAD_SHARED(tail->p) == &head->node;
+ return uatomic_load(&head->node.next, CMM_CONSUME) == NULL
+ && uatomic_load(&tail->p, CMM_CONSUME) == &head->node;
}
static inline void _cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
+ struct cds_wfcq_tail *tail __attribute__((unused)))
{
int ret;
ret = pthread_mutex_lock(&head->lock);
- assert(!ret);
+ urcu_posix_assert(!ret);
}
static inline void _cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
- struct cds_wfcq_tail *tail)
+ struct cds_wfcq_tail *tail __attribute__((unused)))
{
int ret;
ret = pthread_mutex_unlock(&head->lock);
- assert(!ret);
+ urcu_posix_assert(!ret);
}
static inline bool ___cds_wfcq_append(cds_wfcq_head_ptr_t u_head,
* stores to data structure containing node and setting
* node->next to NULL before publication.
*/
- old_tail = uatomic_xchg(&tail->p, new_tail);
+ old_tail = uatomic_xchg_mo(&tail->p, new_tail, CMM_SEQ_CST);
/*
* Implicit memory barrier after uatomic_xchg() orders store to
* store will append "node" to the queue from a dequeuer
* perspective.
*/
- CMM_STORE_SHARED(old_tail->next, new_head);
+ uatomic_store(&old_tail->next, new_head, CMM_RELEASE);
+
/*
* Return false if queue was empty prior to adding the node,
* else return true.
/*
* cds_wfcq_enqueue: enqueue a node into a wait-free queue.
*
- * Issues a full memory barrier before enqueue. No mutual exclusion is
- * required.
+ * Operations prior to enqueue are consistant with respect to dequeuing or
+ * splicing and iterating.
*
* Returns false if the queue was empty prior to adding the node.
* Returns true otherwise.
struct cds_wfcq_tail *tail,
struct cds_wfcq_node *new_tail)
{
+ cmm_emit_legacy_smp_mb();
+
return ___cds_wfcq_append(head, tail, new_tail, new_tail);
}
+/*
+ * CDS_WFCQ_WAIT_SLEEP:
+ *
+ * By default, this sleeps for the given @msec milliseconds.
+ * This is a macro which LGPL users may #define themselves before
+ * including wfcqueue.h to override the default behavior (e.g.
+ * to log a warning or perform other background work).
+ */
+#ifndef CDS_WFCQ_WAIT_SLEEP
+#define CDS_WFCQ_WAIT_SLEEP(msec) ___cds_wfcq_wait_sleep(msec)
+#endif
+
+static inline void ___cds_wfcq_wait_sleep(int msec)
+{
+ (void) poll(NULL, 0, msec);
+}
+
/*
* ___cds_wfcq_busy_wait: adaptative busy-wait.
*
if (!blocking)
return 1;
if (++(*attempt) >= WFCQ_ADAPT_ATTEMPTS) {
- (void) poll(NULL, 0, WFCQ_WAIT); /* Wait for 10ms */
+ CDS_WFCQ_WAIT_SLEEP(WFCQ_WAIT); /* Wait for 10ms */
*attempt = 0;
} else {
caa_cpu_relax();
/*
* Adaptative busy-looping waiting for enqueuer to complete enqueue.
+ *
+ * Load node.next before loading node's content
*/
- while ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ while ((next = uatomic_load(&node->next, CMM_CONSUME)) == NULL) {
if (___cds_wfcq_busy_wait(&attempt, blocking))
return CDS_WFCQ_WOULDBLOCK;
}
if (_cds_wfcq_empty(__cds_wfcq_head_cast(head), tail))
return NULL;
node = ___cds_wfcq_node_sync_next(&head->node, blocking);
- /* Load head->node.next before loading node's content */
- cmm_smp_read_barrier_depends();
+
return node;
}
}
static inline struct cds_wfcq_node *
-___cds_wfcq_next(cds_wfcq_head_ptr_t head,
+___cds_wfcq_next(cds_wfcq_head_ptr_t head __attribute__((unused)),
struct cds_wfcq_tail *tail,
struct cds_wfcq_node *node,
int blocking)
* out if we reached the end of the queue, we first check
* node->next as a common case to ensure that iteration on nodes
* do not frequently access enqueuer's tail->p cache line.
+ *
+ * Load node->next before loading next's content
*/
- if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
- /* Load node->next before tail->p */
- cmm_smp_rmb();
- if (CMM_LOAD_SHARED(tail->p) == node)
+ if ((next = uatomic_load(&node->next, CMM_CONSUME)) == NULL) {
+ if (uatomic_load(&tail->p, CMM_RELAXED) == node)
return NULL;
next = ___cds_wfcq_node_sync_next(node, blocking);
}
- /* Load node->next before loading next's content */
- cmm_smp_read_barrier_depends();
+
return next;
}
return CDS_WFCQ_WOULDBLOCK;
}
- if ((next = CMM_LOAD_SHARED(node->next)) == NULL) {
+ if ((next = uatomic_load(&node->next, CMM_CONSUME)) == NULL) {
/*
* @node is probably the only node in the queue.
* Try to move the tail to &q->head.
* NULL if the cmpxchg succeeds. Should the
* cmpxchg fail due to a concurrent enqueue, the
* q->head.next will be set to the next node.
- * The implicit memory barrier before
- * uatomic_cmpxchg() orders load node->next
- * before loading q->tail.
- * The implicit memory barrier before uatomic_cmpxchg
- * orders load q->head.next before loading node's
- * content.
*/
- _cds_wfcq_node_init(&head->node);
- if (uatomic_cmpxchg(&tail->p, node, &head->node) == node) {
+ _cds_wfcq_node_init_atomic(&head->node);
+ if (uatomic_cmpxchg_mo(&tail->p, node, &head->node,
+ CMM_SEQ_CST, CMM_SEQ_CST) == node) {
if (state)
*state |= CDS_WFCQ_STATE_LAST;
+ cmm_emit_legacy_smp_mb();
return node;
}
next = ___cds_wfcq_node_sync_next(node, blocking);
* (currently NULL) back to its original value.
*/
if (!blocking && next == CDS_WFCQ_WOULDBLOCK) {
- head->node.next = node;
+ uatomic_store(&head->node.next, node, CMM_RELAXED);
return CDS_WFCQ_WOULDBLOCK;
}
}
/*
* Move queue head forward.
*/
- head->node.next = next;
+ uatomic_store(&head->node.next, next, CMM_RELAXED);
+ cmm_emit_legacy_smp_mb();
- /* Load q->head.next before loading node's content */
- cmm_smp_read_barrier_depends();
return node;
}
/*
* __cds_wfcq_splice: enqueue all src_q nodes at the end of dest_q.
*
+ * Operations after splice are consistant with respect to enqueue.
+ *
* Dequeue all nodes from src_q.
* dest_q must be already initialized.
* Mutual exclusion for src_q should be ensured by the caller as
* uatomic_xchg, as well as tail pointer vs head node
* address.
*/
- head = uatomic_xchg(&src_q_head->node.next, NULL);
+ head = uatomic_xchg_mo(&src_q_head->node.next, NULL, CMM_SEQ_CST);
if (head)
break; /* non-empty */
- if (CMM_LOAD_SHARED(src_q_tail->p) == &src_q_head->node)
+ if (uatomic_load(&src_q_tail->p, CMM_CONSUME) == &src_q_head->node)
return CDS_WFCQ_RET_SRC_EMPTY;
if (___cds_wfcq_busy_wait(&attempt, blocking))
return CDS_WFCQ_RET_WOULDBLOCK;
* concurrent enqueue on src_q, which exchanges the tail before
* updating the previous tail's next pointer.
*/
- tail = uatomic_xchg(&src_q_tail->p, &src_q_head->node);
+ cmm_emit_legacy_smp_mb();
+ tail = uatomic_xchg_mo(&src_q_tail->p, &src_q_head->node, CMM_SEQ_CST);
/*
* Append the spliced content of src_q into dest_q. Does not
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