Commit 5c51dd73 authored Aug 04, 2011 by Paul E. McKenney Committed by Paul E. McKenney Sep 28, 2011

rcu: Prevent early boot set_need_resched() from __rcu_pending()

There isn't a whole lot of point in poking the scheduler before there
are other tasks to switch to. This commit therefore adds a check
for rcu_scheduler_fully_active in __rcu_pending() to suppress any
pre-scheduler calls to set_need_resched(). The downside of this approach
is additional runtime overhead in a reasonably hot code path.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent 4627e240

kernel/rcutree.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1707,7 +1707,8 @@ static int __rcu_pending(struct rcu_state rsp, struct rcu_data rdp)
		check_cpu_stall(rsp, rdp);

		/* Is the RCU core waiting for a quiescent state from this CPU? */
		if (rdp->qs_pending && !rdp->passed_quiesce) {
		if (rcu_scheduler_fully_active &&
		rdp->qs_pending && !rdp->passed_quiesce) {

		/*
		* If force_quiescent_state() coming soon and this CPU