diff mbox

[tip/core/rcu,11/23] rcu: Allow RCU quiescent-state forcing to be preempted

Message ID 1348166900-18716-11-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit b4be093fee0200789df59b6c90e2d099a20f55b3
Headers show

Commit Message

Paul E. McKenney Sept. 20, 2012, 6:48 p.m. UTC 
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

RCU quiescent-state forcing is currently carried out without preemption
points, which can result in excessive latency spikes on large systems
(many hundreds or thousands of CPUs).  This patch therefore inserts
a voluntary preemption point into force_qs_rnp(), which should greatly
reduce the magnitude of these spikes.

Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
---
 kernel/rcutree.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
diff mbox

Patch

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index dbf9cc3..b353d32 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1765,6 +1765,7 @@  static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
 	struct rcu_node *rnp;
 
 	rcu_for_each_leaf_node(rsp, rnp) {
+		cond_resched();
 		mask = 0;
 		raw_spin_lock_irqsave(&rnp->lock, flags);
 		if (!rcu_gp_in_progress(rsp)) {