From 41e1172898c515ada8580bbaec7713253cfaa241 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 21 Jun 2015 23:51:21 +0530 Subject: 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 Reviewed-by: Josh Triplett Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git Git-commit: 1eafd31c640d6799c63136246a59d608bed93c74 [kishank@codeaurora.org resolve trivial conflicts] Signed-off-by: Kishan Kumar Signed-off-by: Pranav Vashi Change-Id: I1fdcf6664fdc7dce188488f05f33931e3614c853 --- kernel/rcutree.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 20026ec30..6c0c5ede0 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1590,10 +1590,12 @@ 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. */ - irq_work_queue(&rsp->wakeup_work); + if (current != rsp->gp_kthread) + irq_work_queue(&rsp->wakeup_work); } /* -- cgit v1.2.3