linux-kernel - Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen tasks really

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Message-ID: <20090717162001.GC5878@count0.beaverton.ibm.com>
Date:	Fri, 17 Jul 2009 09:20:01 -0700
From:	Matt Helsley <matthltc@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Matt Helsley <matthltc@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rafael Wysocki <rjw@...k.pl>, Ingo Molnar <mingo@...e.hu>,
	Nathan Lynch <ntl@...ox.com>,
	Nigel Cunningham <nigel@...onice.net>, stable@...nel.org,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen
	tasks really

On Fri, Jul 17, 2009 at 05:55:27PM +0200, Peter Zijlstra wrote:
> On Fri, 2009-07-17 at 08:51 -0700, Matt Helsley wrote:
> 
> > So it's not clear to me how adding PF_FREEZING fixes anything. Am I
> > missing something?
> 
> Yep, PF_FROZEN is only observed going into schedule(), on the way back
> out thaw_process() will already have cleared the flag.
> 
> So we don't increment in deactivate_task(), but we do decrement in
> activate_task(), yielding for some very unbalanced accounting.

Ahhh, right!

OK, so the fix looks good then.

Cheers,
	-Matt Helsley
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