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

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Message-Id: <1247864065.17553.28.camel@localhost.localdomain>
Date:	Fri, 17 Jul 2009 15:54:25 -0500
From:	Nathan Lynch <ntl@...ox.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rafael Wysocki <rjw@...k.pl>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Nigel Cunningham <nigel@...onice.net>, stable@...nel.org,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org,
	Matt Helsley <matthltc@...ibm.com>
Subject: Re: [patch 2/2] sched: fix nr_uninterruptible accounting of frozen
 tasks really

On Fri, 2009-07-17 at 12:25 +0000, Thomas Gleixner wrote:
> commit e3c8ca8336 (sched: do not count frozen tasks toward load) broke
> the nr_uninterruptible accounting on freeze/thaw. On freeze the task
> is excluded from accounting with a check for (task->flags &
> PF_FROZEN), but that flag is cleared before the task is thawed. So
> while we prevent that the freezing task with state
> TASK_UNINTERRUPTIBLE is accounted to nr_uninterruptible we decrement
> nr_uninterruptible on thaw.
> 
> Use a separate flag which is handled by the freezing task itself. Set
> it before calling the scheduler with TASK_UNINTERRUPTIBLE state and
> clear it after we return from frozen state.

Thanks for the fix, and sorry for the regression.  I'll test this early
next week but I don't anticipate any problems for the use case the
original patch was addressing.


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