On Wed, 3 Dec 2014, Dave Jones wrote:
> On Wed, Dec 03, 2014 at 11:19:11PM +0100, Thomas Gleixner wrote:
> > On Wed, 3 Dec 2014, Linus Torvalds wrote:
> > > On Wed, Dec 3, 2014 at 12:55 PM, Thomas Gleixner <t...@linutronix.de>
> wrote:
> > > >
> > > > But it's always negative, which means HPET is always ahead of
> > > > TSC. That excludes pretty much the clocksource watchdog starvation
> > > > issue which results in TSC being ahead of HPET due to a HPET
> > > > wraparound (which takes ~300s).
> > >
> > > Still, I'd be more likely to trust the TSC than the HPET on modern
> > > machines.. And DaveJ's machine isn't some old one.
> >
> > Well, that does not explain the softlock watchdog which is solely
> > relying on the TSC.
> >
> > > Of course, there's always BIOS games. Can we read the TSC offset
> > > register and check it being constant (modulo sleep events)?
> >
> > The kernel does not touch it. Here is a untested hack to verify it on
> > every local apic timer interrupt. Not nice, but simple :)
>
> > + pr_err("TSC adjustment on cpu %d changed %llu ->
> %llu\n",
> > + cpu,
> > + (unsigned long long) __this_cpu_read(tsc_adjust),
> > + (unsigned long long) adj);
>
> I just got
>
> [ 1472.614433] Clocksource tsc unstable (delta = -26373048906 ns)
>
> without any sign of the pr_err above.
Bah. Would have been too simple ....
Could you please run Ingos time-warp test on that machine for a while?
http://people.redhat.com/mingo/time-warp-test/time-warp-test.c
Please change:
- #define TEST_CLOCK 0
+ #define TEST_CLOCK 1
I'll dig further into the time/clocksource whatever related changes
post 3.16
Thanks,
tglx
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