linux-kernel - Re: Help needed: Resume problems in 2.6.32-rc, perhaps related to preempt

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Message-ID: <alpine.LFD.2.00.0911092012340.2725@localhost.localdomain>
Date:	Mon, 9 Nov 2009 20:13:51 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: Help needed: Resume problems in 2.6.32-rc, perhaps related to
 preempt_count leakage in keventd

On Mon, 9 Nov 2009, Rafael J. Wysocki wrote:
> On Monday 09 November 2009, Mike Galbraith wrote:
> > On Mon, 2009-11-09 at 16:47 +0100, Rafael J. Wysocki wrote:
> > > On Monday 09 November 2009, Mike Galbraith wrote:
> > 
> > > > > Very likely.  What did you do to fix it?
> > > > 
> > > > You don't really wanna know.  In 31 with newidle enabled, the below
> > > > fixed it.  It won't fix 32, though it might cure the resume problem.
> > > 
> > > OK, I'll give it a try.
> 
> It doesn't help.
> 
> Also, I can reproduce the issue with current -git and kernel preepmtion
> disabled.
> 
> > I just tried to trigger badness via high speed online/offline combined
> > with taskset with CONFIG_PREEMPT enabled, and couldn't make it explode.
> 
> I'm not able to do it this way too, so resume seems to be necessary to trigger
> it.  I'm going try with the suspend debug in the "core" mode.
> 
> > (damn, wish i could s2ram this box)
> 
> That need not suffice.  I have two other boxes that suspend and resume
> correctly with 2.6.32-rc, AFAICS.
> 
> However, there seems to be a systematic error somewhere, since the failure
> always happens at the same place, ie. list_del_init(cwq->worklist.next); in
> run_workqueue(), in preemptible as well as in non-preemptible kernels.
> 
> Which is kind of strange, given the !list_empty(&cwq->worklist) test right
> before it.

Hmm, no. list_empty() just tells you whether the list is empty or
not. It does not care whether the list is corrupted or not. Have you
tried to run with list debugging enabled ?

Thanks,

	tglx
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