From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH RT 01/16] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock Date: Mon, 09 Sep 2013 08:45:32 -0400 Message-ID: <20130909124555.974389218@goodmis.org> References: <20130909124531.445392664@goodmis.org> Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , To: linux-kernel@vger.kernel.org, linux-rt-users Return-path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:25990 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753593Ab3IIN0y (ORCPT ); Mon, 9 Sep 2013 09:26:54 -0400 Content-Disposition: inline; filename=0001-sched-workqueue-Only-wake-up-idle-workers-if-not-blo.patch Sender: linux-rt-users-owner@vger.kernel.org List-ID: From: Steven Rostedt In -rt, most spin_locks() turn into mutexes. One of these spin_lock conversions is performed on the workqueue gcwq->lock. When the idle worker is worken, the first thing it will do is grab that same lock and it too will block, possibly jumping into the same code, but because nr_running would already be decremented it prevents an infinite loop. But this is still a waste of CPU cycles, and it doesn't follow the method of mainline, as new workers should only be woken when a worker thread is truly going to sleep, and not just blocked on a spin_lock(). Check the saved_state too before waking up new workers. Cc: stable-rt@vger.kernel.org Signed-off-by: Steven Rostedt Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 751ec60..8674878 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3528,8 +3528,10 @@ static inline void sched_submit_work(struct task_struct *tsk) /* * If a worker went to sleep, notify and ask workqueue whether * it wants to wake up a task to maintain concurrency. + * Only call wake up if prev isn't blocked on a sleeping + * spin lock. */ - if (tsk->flags & PF_WQ_WORKER) + if (tsk->flags & PF_WQ_WORKER && !tsk->saved_state) wq_worker_sleeping(tsk); /* -- 1.7.10.4