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

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Date:	Mon, 09 Nov 2009 15:16:16 +0100
From:	Mike Galbraith <efault@....de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	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, 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.

	-Mike

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