Re: [RFC v2 6/7] touch softlockup watchdog

Jeremy Fitzhardinge
2010-08-30T17:33:30Z

On 08/30/2010 09:06 AM, Glauber Costa wrote:
> With a reliable steal time mechanism, we can tell if we're
> out of the cpu for very long, differentiating from the case
> that we simply got a real softlockup.
>
> In the case we were out of cpu, the watchdog is fed, making
> bogus softlockups disappear.

Why not change the softlockup to measure unstolen time rather than
explicitly poking it from a hypervisor-specific function?

How is touching it in kvm_get_steal_time() correct anyway?

J

> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
> arch/x86/kernel/kvmclock.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index a1f4852..d217475 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -91,6 +91,7 @@ cputime_t kvm_get_steal_time(void)
> {
> u64 delta = 0;
> u64 *last_steal_info, this_steal_info;
> + int touch_wd;
> struct pvclock_vcpu_time_info *src;
>
> src = &get_cpu_var(hv_clock);
> @@ -104,6 +105,10 @@ cputime_t kvm_get_steal_time(void)
>
> delta = this_steal_info - *last_steal_info;
>
> + touch_wd = softlockup_thresh * 1000UL;
> + if ((touch_wd > 0) && (delta > touch_wd))
> + touch_softlockup_watchdog();
> +
> *last_steal_info = this_steal_info;
> put_cpu_var(steal_info);
>