linux-kernel - Re: workqueue: WARN at at kernel/workqueue.c:2176

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Date:	Wed, 4 Jun 2014 08:49:46 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	jjherne@...ux.vnet.ibm.com, Sasha Levin <sasha.levin@...cle.com>,
	Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: workqueue: WARN at at kernel/workqueue.c:2176

On Wed, Jun 04, 2014 at 10:27:25AM +0800, Lai Jiangshan wrote:
> > Hmm, yes I think you're right. A queued wakeup can miss an affinity
> > change like that.
> > 
> > Something like the below ought to cure that I suppose..
> 
> As a non-scheduler developer, I can't find anything wrong with the patch
> (I searched all on_rq in kernel/sched).

You did fine finding that hole, so who knows, you might become one real
soon now ;-)

> but I think __migrate_task() is slow path comparing to sched_ttwu_pending().
> So I prefer to change set_cpus_allowed_ptr() and __migrate_task() rather than
> to sched_ttwu_pending().

Yes, I agree, something there would be better, but I couldn't find
anything without holes in.



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