From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
RT <linux-rt-users@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH RT] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock
Date: Fri, 3 May 2013 17:53:40 +0200 [thread overview]
Message-ID: <20130503155340.GD8230@linutronix.de> (raw)
In-Reply-To: <1363633969.28194.3.camel@gandalf.local.home>
* Steven Rostedt | 2013-03-18 15:12:49 [-0400]:
>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.
>
>Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Taking for v3.8-rt.
Sebastian
prev parent reply other threads:[~2013-05-03 15:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-18 19:12 [PATCH RT] sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock Steven Rostedt
2013-05-03 15:53 ` Sebastian Andrzej Siewior [this message]
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