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SubjectRe: [PATCH v2 0/2] Quieten softlockup detector on virtualised kernels
On Fri, Jan 09, 2015 at 02:34:36PM +1100, Cyril Bur wrote:
> When the hypervisor pauses a virtualised kernel the kernel will observe a jump
> in timebase, this can cause spurious messages from the softlockup detector.
>
> Whilst these messages are harmless, they are accompanied with a stack trace
> which causes undue concern and more problematically the stack trace in the
> guest has nothing to do with the observed problem and can only be misleading.

Originally I was suggesting to talk with the x86/kvm folks about coming up
with a common solution. But I didn't hear a response from those cc'd at
the time. This solution looks a lot cleaner than what x86 is doing.

I am willing to see how this works out on ppc64's kvm and see if they still
see any issues after awhile. If not, maybe I can poke the x86 folks to
migrate to something similar.

Acked-by: Don Zickus <dzickus@redhat.com>

>
> Futhermore, on POWER8 this is completely avoidable with the introduction of
> the Virtual Time Base (VTB) register.
>
> V2:
> Remove the export of running_clock
> Added #ifdef CONFIG_PPC_PSERIES and optimised the non lpar + vtb cases.
> Replaced the use of sched_clock_with local_clock it was used originally in
> the softlockup detector.
>
> Cyril Bur (2):
> Add another clock for use with the soft lockup watchdog.
> powerpc: add running_clock for powerpc to prevent spurious softlockup
> warnings
>
> arch/powerpc/kernel/time.c | 32 ++++++++++++++++++++++++++++++++
> include/linux/sched.h | 1 +
> kernel/sched/clock.c | 13 +++++++++++++
> kernel/watchdog.c | 2 +-
> 4 files changed, 47 insertions(+), 1 deletion(-)
>
> --
> 1.9.1
>


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