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SubjectRe: [patch] fix the softlockup watchdog to actually work
On 7/17/07, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>
> > Ingo Molnar wrote:
> > > Subject: softlockup: fix Xen bogosity
> > > From: Ingo Molnar <mingo@elte.hu>
> > >
> > > 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"?
>
> uhm, the problem was that it did not work _at all_, not something about
> 'rate limiting'. Yes, i got quite a bit grumpy when i found this,
> because you completely broke the softlockup watchdog via a pretty
> intrusive commit and you apparently didnt even do a minimal check
> whether its functionality was preserved! Updated patch for Andrew/Linus
> and for -stable attached.
>
> Ingo
>
> ----------------------------->
> Subject: fix the softlockup watchdog to actually work
> From: Ingo Molnar <mingo@elte.hu>
>
> this Xen related commit:
>
> commit 966812dc98e6a7fcdf759cbfa0efab77500a8868
> Author: Jeremy Fitzhardinge <jeremy@goop.org>
> 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 in essence 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@elte.hu>
> ---
> 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;
> + }
>
> /* do not print during early bootup: */
> if (unlikely(system_state != SYSTEM_RUNNING)) {
> -

how about

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index 708d488..bbc0292 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -80,7 +80,7 @@ void softlockup_tick(void)
print_timestamp = per_cpu(print_timestamp, this_cpu);

/* report at most once a second */
- if (print_timestamp < (touch_timestamp + 1) ||
+ if (((touch_timestamp - print_timestamp) < 1) ||
did_panic ||
!per_cpu(watchdog_task, this_cpu))

YH
-
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