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().
* 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,
* 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);
}
/*
* 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;
}
* 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
projects / urcu.git / blobdiff