linux-kernel - Re: rc5+tip/master: Marking clocksource 'tsc' as unstable because the skew is too large:

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Date:	Thu, 30 Jun 2016 11:42:57 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
cc:	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>, x86-ml <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: rc5+tip/master: Marking clocksource 'tsc' as unstable because
 the skew is too large:

On Thu, 30 Jun 2016, Mike Galbraith wrote:
> On Thu, 2016-06-30 at 10:41 +0200, Thomas Gleixner wrote:
> > On Thu, 30 Jun 2016, Mike Galbraith wrote:
> > 
> > > On Wed, 2016-06-29 at 19:16 +0200, Borislav Petkov wrote:
> > > 
> > > > And here it is again:
> > > > 
> > > > ...
> > > > [   15.720833] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes
> > ready
> > > > [   32.883077] clocksource: timekeeping watchdog on CPU1: Marking
> > clocksource 'tsc' as unstable because the skew is too large:
> > > > [   32.896986] clocksource:                       'acpi_pm'
> > wd_now: 8e147 wd_last: 531b43 mask: ffffff
> > > > [   32.908834] clocksource:                       'tsc' cs_now:
> > 385f4b6d1e cs_last: 354328bcea mask: ffffffffffffffff
> > > > [   32.922293] clocksource: Switched to clocksource acpi_pm
> > > 
> > > I met that too when testing, but only on my 8 socket box for
> > whatever
> > > reason.  Putting tip back on the box and poking a bit while I beat
> > up
> > > rt kernels elsewhere, cs_nsec: 167001172874 wd_nsec: 0.  (poke++)
> > 
> > can i get the full data please including tsc frequency?
> 
> [    0.000000] tsc: Fast TSC calibration using PIT
> [    0.000000] tsc: Detected 2260.928 MHz processor
> [   13.205453] tsc: Refined TSC clocksource calibration: 2260.999 MHz
> [   13.205457] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x20974a4d8bb, max_idle_ns: 440795246623 ns
> [   14.592866] clocksource: Switched to clocksource tsc
> [  575.781329] clocksource: timekeeping watchdog on CPU23: Marking clocksource 'tsc' as unstable because the skew is too large:
> [  575.998835] clocksource:                       'tsc' cs_now: 1c1effead80 cs_last: 139efdabfa5 mask: ffffffffffffffff
> 
> trace_printk() leading to splat (hm, mask).
>           <idle>-0     [023] ..s.    25.233237: clocksource_watchdog: cs_nsec: 511311920 wd_nsec: 511311599 delta: 321 wdnow: 362266206  cs->wd_last: 354945155 watchdog->mask: ffffffff
>           <idle>-0     [023] ..s.    57.234242: clocksource_watchdog: cs_nsec: 511999944 wd_nsec: 511999396 delta: 548 wdnow: 820447848  cs->wd_last: 813116949 watchdog->mask: ffffffff
>           <idle>-0     [023] ..s.   575.781321: clocksource_watchdog: cs_nsec: 258345057292 wd_nsec: 0 delta: 258345057292 wdnow: 3949895484  cs->wd_last: 250865676 watchdog->mask: ffffffff
> 

So there was no watchdog firing for 525 seconds ????