From: Frederic Weisbecker <fweisbec@gmail.com>
To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org,
peterz@infradead.org, sergey.senozhatsky@gmail.com, bp@alien8.de,
paulmck@linux.vnet.ibm.com, tglx@linutronix.de,
sgruszka@redhat.com
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:timers/urgent] sched/cputime: Do not scale when utime == 0
Date: Wed, 4 Sep 2013 17:35:08 +0200 [thread overview]
Message-ID: <20130904153507.GC2308@somewhere> (raw)
In-Reply-To: <tip-5a8e01f8fa51f5cbce8f37acc050eb2319d12956@git.kernel.org>
On Wed, Sep 04, 2013 at 07:37:22AM -0700, tip-bot for Stanislaw Gruszka wrote:
> Commit-ID: 5a8e01f8fa51f5cbce8f37acc050eb2319d12956
> Gitweb: http://git.kernel.org/tip/5a8e01f8fa51f5cbce8f37acc050eb2319d12956
> Author: Stanislaw Gruszka <sgruszka@redhat.com>
> AuthorDate: Wed, 4 Sep 2013 15:16:03 +0200
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Wed, 4 Sep 2013 16:31:25 +0200
>
> sched/cputime: Do not scale when utime == 0
>
> scale_stime() silently assumes that stime < rtime, otherwise
> when stime == rtime and both values are big enough (operations
> on them do not fit in 32 bits), the resulting scaling stime can
> be bigger than rtime. In consequence utime = rtime - stime
> results in negative value.
>
> User space visible symptoms of the bug are overflowed TIME
> values on ps/top, for example:
>
> $ ps aux | grep rcu
> root 8 0.0 0.0 0 0 ? S 12:42 0:00 [rcuc/0]
> root 9 0.0 0.0 0 0 ? S 12:42 0:00 [rcub/0]
> root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt]
> root 11 0.1 0.0 0 0 ? S 12:42 0:02 [rcuop/0]
> root 12 62422329 0.0 0 0 ? S 12:42 21114581:35 [rcuop/1]
> root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt]
>
> or overflowed utime values read directly from /proc/$PID/stat
>
> Reference:
>
> https://lkml.org/lkml/2013/8/20/259
>
> Reported-and-tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> Cc: stable@vger.kernel.org
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Link: http://lkml.kernel.org/r/20130904131602.GC2564@redhat.com
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Thanks a lot guys!
next prev parent reply other threads:[~2013-09-04 15:35 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-20 11:14 [sched next] overflowed cpu time for kernel threads in /proc/PID/stat Sergey Senozhatsky
2013-08-20 15:15 ` Frederic Weisbecker
2013-08-20 15:35 ` Sergey Senozhatsky
2013-08-20 15:42 ` Frederic Weisbecker
2013-08-20 15:53 ` Sergey Senozhatsky
2013-08-20 18:48 ` Sergey Senozhatsky
2013-08-21 15:39 ` Sergey Senozhatsky
2013-08-30 23:04 ` Frederic Weisbecker
2013-08-31 19:01 ` Sergey Senozhatsky
2013-09-08 10:56 ` Frederic Weisbecker
2013-09-08 10:59 ` Frederic Weisbecker
2013-09-02 12:28 ` Sergey Senozhatsky
2013-09-02 13:07 ` Frederic Weisbecker
2013-09-02 13:39 ` Sergey Senozhatsky
2013-09-02 13:50 ` Stanislaw Gruszka
2013-09-02 14:00 ` Sergey Senozhatsky
2013-09-03 8:43 ` Stanislaw Gruszka
2013-09-03 9:33 ` Sergey Senozhatsky
2013-09-03 13:15 ` Sergey Senozhatsky
2013-09-03 18:09 ` Sergey Senozhatsky
2013-09-03 18:32 ` Ingo Molnar
2013-09-04 12:08 ` [PATCH -tip] sched/cputime: do not scale when utime == 0 Stanislaw Gruszka
2013-09-04 12:33 ` Ingo Molnar
2013-09-04 13:16 ` [PATCH -tip v2] " Stanislaw Gruszka
2013-09-04 14:31 ` Ingo Molnar
2013-09-04 14:37 ` [tip:timers/urgent] sched/cputime: Do " tip-bot for Stanislaw Gruszka
2013-09-04 15:35 ` Frederic Weisbecker [this message]
2013-09-02 14:13 ` [sched next] overflowed cpu time for kernel threads in /proc/PID/stat Frederic Weisbecker
2013-09-02 14:24 ` Sergey Senozhatsky
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