Re: [patch] softlockup watchdog: fix Xen bogosity

From: Jeremy Fitzhardinge
Date: Tue Jul 17 2007 - 10:24:30 EST


Ingo Molnar wrote:
> Subject: softlockup: fix Xen bogosity
> From: Ingo Molnar <mingo@xxxxxxx>
>
> this Xen related commit:
>

Well, not just Xen. It relates to any virtual environment: kvm, lguest,
vmi, xen... (Not that they all implement a measure of unstolen time.)

How about a more descriptive patch title, along the lines of "softlockup
watchdog: fix rate limiting"?

> commit 966812dc98e6a7fcdf759cbfa0efab77500a8868
> Author: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> Date: Tue May 8 00:28:02 2007 -0700
>
> Ignore stolen time in the softlockup watchdog
>
> broke the softlockup watchdog to never report any lockups. (!)
>
> print_timestamp defaults to 0, this makes the following condition
> always true:
>
> if (print_timestamp < (touch_timestamp + 1) ||
>
> and we'll never report soft lockups.
>
> apparently the functionality of the soft lockup watchdog was never
> actually tested with that patch applied ...
>
> [ this is -stable material too. ]
>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> ---
> kernel/softlockup.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> Index: linux/kernel/softlockup.c
> ===================================================================
> --- linux.orig/kernel/softlockup.c
> +++ linux/kernel/softlockup.c
> @@ -79,10 +79,11 @@ void softlockup_tick(void)
> print_timestamp = per_cpu(print_timestamp, this_cpu);
>
> /* report at most once a second */
> - if (print_timestamp < (touch_timestamp + 1) ||
> - did_panic ||
> - !per_cpu(watchdog_task, this_cpu))
> + if ((print_timestamp >= touch_timestamp &&
> + print_timestamp < (touch_timestamp + 1)) ||
> + did_panic || !per_cpu(watchdog_task, this_cpu)) {
> return;
> + }
>

OK, thanks.

Acked-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>

J
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