linux-kernel - Re: [3.6-rc1] sched: clock counts too quickly

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Message-Id: <201208042246.HBH81275.FVOOSLtJFMQOFH@I-love.SAKURA.ne.jp>
Date:	Sat, 4 Aug 2012 22:46:08 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	john.stultz@...aro.org, mingo@...nel.org, tglx@...utronix.de
Cc:	a.p.zijlstra@...llo.nl, richardcochran@...il.com,
	prarit@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [3.6-rc1] sched: clock counts too quickly

Hello.

Bisected to 2a8c0883 "time: Move xtime_nsec adjustment underflow handling
timekeeping_adjust".

Would you check?

Regards.

Tetsuo Handa wrote:
> Tetsuo Handa wrote:
> > > Under unknown condition, clock starts counting up too quickly which is enough
> > > to confuse hangcheck timer to print stall warning.
> > I wrote a test program.
> 
> I suspected that this is a problem within adjtimex() because strace reported clock
> jump at adjtimex(). But I've just hit this problem with settimeofday() alone.
> 
> ---------- test program 2 start ----------
> #include <sys/timex.h>
> 
> int main(int argc, char *argv[])
> {
>         while (1) {
>                 struct timeval tv;
>                 struct timezone tz;
>                 gettimeofday(&tv, &tz);
>                 settimeofday(&tv, &tz);
>         }
>         return 0;
> }
> ---------- test program 2 end ----------
> 
> Regards.
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