linux-kernel - Re: [PATCH 1/3] posix-timers: Correctly get dying task time sample in posix_cpu_timer

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Message-ID: <5158CFDF.4060700@asianux.com>
Date:	Mon, 01 Apr 2013 08:07:59 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 1/3] posix-timers: Correctly get dying task time sample
 in posix_cpu_timer_schedule()

On 2013年03月30日 21:15, Frederic Weisbecker wrote:
> In order to arm the next timer to schedule, we take a sample of the
> current process or thread cputime.
> 
> If the task is dying though, we don't arm anything but we
> cache the remaining timer expiration delta for further reads.
> 
> Something similar is performed in posix_cpu_timer_get() but
> here we forget to take the process wide cputime sample
> before caching it.
> 
> As a result we are storing random stack content, leading
> every further reads of that timer to return junk values.
> 
> Fix this by taking the appropriate sample in the case of
> process wide timers.
> 
> Reported-by: Andrew Morton <akpm@...ux-foundation.org>
> Reported-by: Chen Gang <gang.chen@...anux.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Stanislaw Gruszka <sgruszka@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Chen Gang <gang.chen@...anux.com>
> ---

  thank you for mark me as reported by, although I reported too late
(Andrew Morton is the first reporter).

  next, I should continue to try to find another issues about kernel.

  :-)

-- 
Chen Gang

Asianux Corporation
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