From: Paul E. McKenney Date: Thu, 20 Jun 2013 20:50:40 +0000 (-0700) Subject: rcu: Avoid redundant grace-period kthread wakeups X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1eafd31c640d6799c63136246a59d608bed93c74;p=linux-beck.git 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 --- diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 91840566e294..c6a064abd6a0 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1576,10 +1576,12 @@ 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); } /*