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Commit b4be093f authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Allow RCU quiescent-state forcing to be preempted 



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: default avatarMike Galbraith <mgalbraith@suse.de>
Reported-by: default avatarDimitri Sivanich <sivanich@sgi.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 4cdfc175

kernel/rcutree.c

+1 −0
Original line number Diff line number Diff line
@@ -1767,6 +1767,7 @@ 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)) {