From: Tejun Heo <tj@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
RT <linux-rt-users@vger.kernel.org>,
Clark Williams <clark@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: workqueue code needing preemption disabled
Date: Mon, 18 Mar 2013 09:46:10 -0700 [thread overview]
Message-ID: <20130318164610.GB21516@mtj.dyndns.org> (raw)
In-Reply-To: <1363624883.25967.184.camel@gandalf.local.home>
On Mon, Mar 18, 2013 at 12:41:23PM -0400, Steven Rostedt wrote:
> But, I'm worried about the loops that are done while holding this lock.
> Just looking at is_chained_work() that does for_each_busy_worker(), how
> big can that list be? If it's bound by # of CPUs then that may be fine,
> but if it can be as big as the # of workers assigned, with no real
> limit, then its not fine, because that creates an unbound (non
> deterministic) latency.
In most paths, gcwq->lock shouldn't be held for too long but yes there
are cold paths which just do things without thinking about latency
issues. is_chained_work() can definitely take pretty long time (note
that it got reimplemented in the current devel branch and the loop is
gone).
--
tejun
prev parent reply other threads:[~2013-03-18 16:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-18 14:36 Steven Rostedt
2013-03-18 16:06 ` Tejun Heo
2013-03-18 16:23 ` Steven Rostedt
2013-03-18 16:27 ` Steven Rostedt
2013-03-18 16:30 ` Steven Rostedt
2013-03-18 16:43 ` Tejun Heo
2013-03-18 17:08 ` Steven Rostedt
2013-03-18 18:21 ` Tejun Heo
2013-03-18 18:57 ` Steven Rostedt
2013-03-18 19:06 ` Tejun Heo
2013-03-18 19:19 ` Steven Rostedt
2013-03-18 18:23 ` Steven Rostedt
2013-03-18 18:26 ` Tejun Heo
2013-03-18 18:35 ` Steven Rostedt
2013-03-18 16:27 ` Tejun Heo
2013-03-18 16:41 ` Steven Rostedt
2013-03-18 16:46 ` Tejun Heo [this message]
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