Messages in this thread | | | Date | Fri, 5 Jul 2013 17:24:09 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [URGENT rfc patch 0/3] tsc clocksource bug fix |
| |
On Fri, 5 Jul 2013, Peter Zijlstra wrote:
> On Fri, Jul 05, 2013 at 04:23:33PM +0200, Frederic Weisbecker wrote: > > Nope, I haven't touched that. I prefer not to fiddle with unstable > > clocksource for now :) > > > > As for unstable TSCs, if sched_clock_tick() needs to be fed, we simply > > don't stop the tick. > > Not entirely the same thing; I thought the clocksource watchdog was ran > even when we have a 'stable' TSC, just to make sure it stays stable. > There's known cases where the BIOS f*cks us over and wrecks TSC sync.
See arch/x86/kernel/tsc.c
We disable the watchdog for the TSC when tsc_clocksource_reliable is set.
tsc_clocksource_reliable is set when:
- you add tsc=reliable to the kernel command line
- boot_cpu_has(X86_FEATURE_TSC_RELIABLE)
X86_FEATURE_TSC_RELIABLE is a software flag, set by vmware and moorsetown. So all other machines keep the watchdog enabled.
- On Geode LX (OLPC)
Thanks,
tglx
| |