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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130904153507.GC2308@somewhere \
--to=fweisbec@gmail.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=sergey.senozhatsky@gmail.com \
--cc=sgruszka@redhat.com \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.