linux-kernel - Re: [2.6.21.1] soft lockup when removing netconsole module

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Date:	Sun, 27 May 2007 15:32:21 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Folkert van Heusden <folkert@...heusden.com>,
	Parag Warudkar <parag.warudkar@...il.com>,
	linux-kernel@...r.kernel.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: [2.6.21.1] soft lockup when removing netconsole module

On Sat, May 26, 2007 at 06:35:24PM +0200, Thomas Gleixner wrote:
> On Sat, 2007-05-26 at 18:17 +0200, Folkert van Heusden wrote:
> > > > Seems to be hrtimers related - CC'ed Thomas.
> > > I doubt that. The tick interrupt just finds out, that the machine is
> > > stuck in rmmod.
> > > > > Also the rmmod hangs and would not exit even with kill -9. It also
> > > > > sucks up 100% cpu.
> > > Can you please enable CONFIG_PROVE_LOCKING ?
> >
> > Luckily I already had :-)
> > Here is its output:
> 
> So there is no output from lockdep, during the rmmod hang ? The rmmod
> sucks 100% cpu, so it busy loops at some place. Looking at the stack
> trace this seems to be in:
> 
> 
> void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,                                                                                                                 
>                                        struct delayed_work *dwork)                                                                                                                  
> {                                                                                                                                                                                   
>         while (!cancel_delayed_work(dwork))                                                                                                                                         
>                 flush_workqueue(wq);                                                                                                                                                
> }
> 
> which is not really related to timers :)

Looks like Steve added the delayed work bits, though I never saw any
of his patches.

-- 
Mathematics is the supreme nostalgia of our time.
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