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

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Message-ID: <20140516102908.GU30445@twins.programming.kicks-ass.net>
Date:	Fri, 16 May 2014 12:29:08 +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 Fri, May 16, 2014 at 05:56:10PM +0800, Lai Jiangshan wrote:
> On 05/16/2014 05:35 PM, Peter Zijlstra wrote:
> > On Fri, May 16, 2014 at 11:50:42AM +0800, Lai Jiangshan wrote:
> >> After debugging, I found the hotlug-in cpu is atctive but !online in this case.
> >> the problem was introduced by 5fbd036b.
> >> Some code assumes that any cpu in cpu_active_mask is also online, but 5fbd036b breaks
> >> this assumption, so the corresponding code with this assumption should be changed too.
> > 
> > Good find, and yes it does that.
> > 
> >> The following patch is just a workaround. After it is applied, the above WARNING
> >> is gone, but I can't hit the wq problem that you found.
> > 
> > Seeing how the entirety of hotplug is basically duct tape and twigs, the
> > below isn't that bad.
> 
> I think we need to find a more grace solution...

A complete rewrite of the hotplug mess, until that time this is fine.



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