From: Chen Gang <gang.chen@asianux.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Stanislaw Gruszka <sgruszka@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@elte.hu>, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 1/3] posix-timers: Correctly get dying task time sample in posix_cpu_timer_schedule()
Date: Mon, 01 Apr 2013 08:07:59 +0800 [thread overview]
Message-ID: <5158CFDF.4060700@asianux.com> (raw)
In-Reply-To: <1364649331-30940-2-git-send-email-fweisbec@gmail.com>
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@linux-foundation.org>
> Reported-by: Chen Gang <gang.chen@asianux.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Stanislaw Gruszka <sgruszka@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Chen Gang <gang.chen@asianux.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
next prev parent reply other threads:[~2013-04-01 0:08 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-30 13:15 [PATCH 0/3] posix_timers: A few expiry caching fixes Frederic Weisbecker
2013-03-30 13:15 ` [PATCH 1/3] posix-timers: Correctly get dying task time sample in posix_cpu_timer_schedule() Frederic Weisbecker
2013-04-01 0:07 ` Chen Gang [this message]
2013-04-11 15:26 ` Frederic Weisbecker
2013-04-11 15:33 ` Chen Gang
2013-03-30 13:15 ` [PATCH 2/3] posix_timers: Fix racy timer delta caching on task exit Frederic Weisbecker
2013-03-30 13:15 ` [PATCH 3/3] posix_timers: Remove dead task timer expiry caching Frederic Weisbecker
2013-04-08 23:55 ` [PATCH 0/3] posix_timers: A few expiry caching fixes Andrew Morton
2013-04-11 15:19 ` Frederic Weisbecker
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