From 23086b720b7edf8b402f22a899568bc6cbcb8235 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 13 Jul 2010 11:59:55 -0400 Subject: [PATCH] RCU lock-free queue: don't hold RCU read lock across retry Be nicer to grace periods. Signed-off-by: Mathieu Desnoyers --- urcu/rculfqueue.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/urcu/rculfqueue.h b/urcu/rculfqueue.h index 32fca49..09e5d41 100644 --- a/urcu/rculfqueue.h +++ b/urcu/rculfqueue.h @@ -72,11 +72,11 @@ void rcu_lfq_enqueue(struct rcu_lfq_queue *q, struct rcu_lfq_node *node) * node before publication. */ - rcu_read_lock(); for (;;) { - struct rcu_lfq_node *tail = rcu_dereference(q->tail); - struct rcu_lfq_node *next; + struct rcu_lfq_node *tail, *next; + rcu_read_lock(); + tail = rcu_dereference(q->tail); /* * Typically expect tail->next to be NULL. */ @@ -97,6 +97,7 @@ void rcu_lfq_enqueue(struct rcu_lfq_queue *q, struct rcu_lfq_node *node) * further and retry. */ uatomic_cmpxchg(&q->tail, tail, next); + rcu_read_unlock(); continue; } } @@ -113,11 +114,12 @@ void rcu_lfq_enqueue(struct rcu_lfq_queue *q, struct rcu_lfq_node *node) struct rcu_lfq_node * rcu_lfq_dequeue(struct rcu_lfq_queue *q, void (*release)(struct urcu_ref *)) { - rcu_read_lock(); for (;;) { - struct rcu_lfq_node *head = rcu_dereference(q->head); - struct rcu_lfq_node *next = rcu_dereference(head->next); + struct rcu_lfq_node *head, *next; + rcu_read_lock(); + head = rcu_dereference(q->head); + next = rcu_dereference(head->next); if (next) { if (uatomic_cmpxchg(&q->head, head, next) == head) { rcu_read_unlock(); @@ -125,6 +127,7 @@ rcu_lfq_dequeue(struct rcu_lfq_queue *q, void (*release)(struct urcu_ref *)) return next; } else { /* Concurrently pushed, retry */ + rcu_read_unlock(); continue; } } else { -- 2.34.1