linux-kernel - Re: [workqueue] WARNING: CPU: 0 PID: 76 at drivers/block/floppy.c:968 schedule

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Message-ID: <alpine.LNX.2.00.1407111526430.8779@pobox.suse.cz>
Date:	Fri, 11 Jul 2014 15:27:34 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Tejun Heo <tj@...nel.org>, Fengguang Wu <fengguang.wu@...el.com>
cc:	Jet Chen <jet.chen@...el.com>, Su Tao <tao.su@...el.com>,
	Yuanhan Liu <yuanhan.liu@...el.com>, LKP <lkp@...org>,
	linux-kernel@...r.kernel.org
Subject: Re: [workqueue] WARNING: CPU: 0 PID: 76 at drivers/block/floppy.c:968
 schedule_bh()

On Tue, 8 Jul 2014, Jiri Kosina wrote:

> > > Hmmm... this is schedule_bh() in floppy.c complaining that the work
> > > item is already pending.  The cond_resched() addition by b22ce2785d97
> > > doesn't change the semantics around work item execution although it
> > > could have exposed an existing problem in the floppy driver.  I'll
> > > look into how this could happen.
> > 
> > It doesn't reproduce here and nothing really stands out to me.  It
> > probably involves floppy_work requeueing itself and something else
> > getting executed inbetween which wouldn't have happend before, but I
> > can't figure out what that could be and either can I follow the
> > control flow the driver. :)
> >
> > 
> > Jiri, any ideas?
> 
> I will take a look. Could this be a bad bisect though due to this actually 
> being a race condition perhaps?

Fengguang, is it possible for you to confirm the bisection result (i.e. 
revert the patch and check)?

I am having hard time seeing how it could cause this (and I am not able to 
reproduce the problem myself).

Thanks,

-- 
Jiri Kosina
SUSE Labs
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