linux-kernel - Re: [sched next] overflowed cpu time for kernel threads in /proc/PID/stat

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Message-ID: <20130908105932.GE4501@somewhere>
Date:	Sun, 8 Sep 2013 12:59:33 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Stanislaw Gruszka <sgruszka@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org
Subject: Re: [sched next] overflowed cpu time for kernel threads in
 /proc/PID/stat

On Sat, Aug 31, 2013 at 10:01:17PM +0300, Sergey Senozhatsky wrote:
> On (08/31/13 01:04), Frederic Weisbecker wrote:
> > But stime should always be below rtime due to the calculation done by scale_stime()
> > which roughly sums up to:
> > 
> >       stime = (stime / stime + utime) * rtime
> > 
> > So this shouldn't happen.
> > 
> > I couldn't manage to reproduce it though. Can you still trigger it with latest -next?
> > 
> > Thanks.
> 
> Hello,
> I can't pull current -next (away from good network connection for a
> couple of days). What I have is 3.11.0-rc7-next-20130829:
> 
> ps aux | grep rcu
> root         8  0.0  0.0      0     0 ?        S    Aug30   0:00 [rcuc/0]
> root         9  0.0  0.0      0     0 ?        S    Aug30   0:00 [rcub/0]
> root        10 21376376  0.0  0     0 ?        S    Aug30 21114581:36 [rcu_preempt]
> root        11 21376376  0.0  0     0 ?        S    Aug30 21114581:35 [rcuop/0]
> root        12 21376376  0.0  0     0 ?        S    Aug30 21114581:35 [rcuop/1]
> 
> cat /proc/10/stat
> 10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 1844674407370 715 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> 
> 	-ss

Sorry, I did not realize this message was posted before you tested the patch.
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