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

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Date:	Mon, 9 Nov 2009 15:27:12 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mike Galbraith <efault@....de>
Cc:	Thomas Gleixner <tglx@...utronix.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 Monday 09 November 2009, Mike Galbraith wrote:
> On Mon, 2009-11-09 at 15:02 +0100, Thomas Gleixner wrote:
> > On Mon, 9 Nov 2009, Ingo Molnar wrote:
> > > 
> 
> > > ok, then my observation should not apply.
> > 
> > I think it _IS_ releated because the worker_thread is CPU affine and
> > the debug_smp_processor_id() check does:
> > 
> >     if (cpumask_equal(&current->cpus_allowed, cpumask_of(this_cpu)))
> > 
> > which prevents that usage of smp_processor_id() in ksoftirqd and
> > keventd in preempt enabled regions is warned on.
> > 
> > We saw exaclty the same back trace with fd21073 (sched: Fix affinity
> > logic in select_task_rq_fair()).
> > 
> > Rafael, can you please add a printk to debug_smp_processor_id() so we
> > can see on which CPU we are running ? I suspect we are on the wrong
> > one.
> 
> I wonder if that's not intimately related to the problem I had, namely
> newidle balancing offline CPUs as they're coming up, making a mess of
> cpu enumeration.

Very likely.  What did you do to fix it?

Rafael
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