From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Sat, 26 Sep 2009 19:10:04 +0000 (-0400)
Subject: urcu-qsbr: repeat sched_yield() loop, yield at offline rather than online.
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=b3c4dd1a5c12b59efdee51be209767a9f406a715;p=userspace-rcu.git

urcu-qsbr: repeat sched_yield() loop, yield at offline rather than online.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

diff --git a/urcu-qsbr-static.h b/urcu-qsbr-static.h
index 1cb4246..9cc5db4 100644
--- a/urcu-qsbr-static.h
+++ b/urcu-qsbr-static.h
@@ -239,18 +239,15 @@ static inline void _rcu_thread_offline(void)
 {
 	smp_mb();
 	STORE_SHARED(urcu_reader_status.qs_gp, 0);
+	if (unlikely(LOAD_SHARED(urcu_gp_ctr) & RCU_GP_ONGOING) &&
+	    unlikely(urcu_reader_status.gp_waiting)) {
+		sched_yield();
+	}
 }
 
 static inline void _rcu_thread_online(void)
 {
-	long gp_ctr;
-
-	if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) &&
-	    unlikely(urcu_reader_status.gp_waiting)) {
-		sched_yield();
-		gp_ctr = LOAD_SHARED(urcu_gp_ctr);
-	}
-	_STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr);
+	_STORE_SHARED(urcu_reader_status.qs_gp, LOAD_SHARED(urcu_gp_ctr));
 	smp_mb();
 }
 
diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index 8828ae8..c275b66 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -118,6 +118,7 @@ static void wait_for_quiescent_state(void)
 		while (rcu_gp_ongoing(&index->urcu_reader_status->qs_gp)) {
 			if (wait_loops++ == RCU_QS_ACTIVE_ATTEMPTS) {
 				sched_yield();	/* ideally sched_yield_to() */
+				wait_loops = 0;
 			} else {
 #ifndef HAS_INCOHERENT_CACHES
 				cpu_relax();