Commit 1eafd31c authored Jun 20, 2013 by Paul E. McKenney

rcu: Avoid redundant grace-period kthread wakeups

When setting up an in-the-future "advanced" grace period, the code needs
to wake up the relevant grace-period kthread, which it currently does
unconditionally. However, this results in needless wakeups in the case
where the advanced grace period is being set up by the grace-period
kthread itself, which is a non-uncommon situation. This commit therefore
checks to see if the running thread is the grace-period kthread, and
avoids doing the irq_work_queue()-mediated wakeup in that case.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

parent ae150184

kernel/rcutree.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -1576,9 +1576,11 @@ rcu_start_gp_advanced(struct rcu_state rsp, struct rcu_node rnp,

		/*
		* We can't do wakeups while holding the rnp->lock, as that
		* could cause possible deadlocks with the rq->lock. Deter
		* the wakeup to interrupt context.
		* could cause possible deadlocks with the rq->lock. Defer
		* the wakeup to interrupt context. And don't bother waking
		* up the running kthread.
		*/
		if (current != rsp->gp_kthread)
		irq_work_queue(&rsp->wakeup_work);
		}