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

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Date:	Sat, 31 Aug 2013 22:01:17 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Frederic Weisbecker <fweisbec@...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 (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
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