linux-kernel - Re: x86-tip tsc/tick gripage

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Message-ID: <1493198295.21594.11.camel@gmx.de>
Date:   Wed, 26 Apr 2017 11:18:15 +0200
From:   Mike Galbraith <efault@....de>
To:     Ingo Molnar <mingo@...nel.org>,
        "Paul E. McKenney" <paulmck@...ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: x86-tip tsc/tick gripage

On Wed, 2017-04-26 at 10:57 +0200, Mike Galbraith wrote:
> On Wed, 2017-04-26 at 10:31 +0200, Mike Galbraith wrote:
> > On Wed, 2017-04-26 at 10:21 +0200, Ingo Molnar wrote:
> > 
> > > I have temporarily removed the current timers/urgent lineup from -tip:
> > > 
> > >  098991fccfc7: nohz: Print more debug info in tick_nohz_stop_sched_tick()
> > >  22aa2ad45fd8: tick: Make sure tick timer is active when bypassing reprogramming
> > >  d58bd60c773d: nohz: Fix again collision between tick and other hrtimers
> > > 
> > > ... and have reintegrated tip:master, so it should be back to working I think.
> > > 
> > > Does this solve the warning and the RCU stalls on your boxes?
> > 
> > (both boxen building)
> 
> (oh come on, boot already... zzz)
> 
> Both still lose their TSC.

Aw crap, and the DL980 RCU stalled while idling again.

> [   11.982468] tsc: Refined TSC clocksource calibration: 2260.999 MHz
> [   11.994275] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x20974a4d8bb, max_idle_ns: 440795246623 ns
> [   13.064172] clocksource: Switched to clocksource tsc
> [  240.247851] clocksource: timekeeping watchdog on CPU23: Marking clocksource 'tsc' as unstable because the skew is too large:
> [  240.462501] clocksource:                       'tsc' cs_now: 108fe5be09f cs_last: b90a6a0676 mask: ffffffffffffffff
> [  240.675057] tsc: Marking TSC unstable due to clocksource watchdog
> 
> [  349.192460] clocksource: timekeeping watchdog on CPU63: Marking clocksource 'tsc' as unstable because the skew is too large:
> [  349.217756] clocksource:                       'hpet' wd_now: 2bb0dad7 wd_last: 5d9ac241 mask: ffffffff
> [  349.239021] clocksource:                       'tsc' cs_now: d2413ebfc1c28 cs_last: d2387b328a38c mask: ffffffffffffffff
> [  349.263525] sched_clock: Marking unstable (349228856508, 34664619)<-(351146178141, -1882657014)
> [  349.283245] tsc: Marking TSC unstable due to clocksource watchdog
> [  349.298075] clocksource: Switched to clocksource hpet