From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] watchdog: revert cleanup handling of false positives
Date: Thu, 20 May 2021 14:13:32 +0900 [thread overview]
Message-ID: <YKXv/CtdWwiqoAHa@google.com> (raw)
In-Reply-To: <YKPfDQoN5hToB9nk@alley>
On (21/05/18 17:36), Petr Mladek wrote:
> On Mon 2021-05-17 23:06:12, Sergey Senozhatsky wrote:
> > This reverts commit 9bf3bc949f8aeefeacea4b1198db833b722a8e27.
> >
> > I can reproduce the case when resumed VCPU starts to execute
> > is_softlockup() with PVCLOCK_GUEST_STOPPED set on this VCPU:
> >
> > watchdog_timer_fn()
> > {
> > ...
> >
> > kvm_check_and_clear_guest_paused();
> >
> > ...
> >
> > duration = is_softlockup(touch_ts, period_ts);
> > if (unlikely(duration)) {
> > ....
> > }
> > }
> >
> > Which means that guest VCPU has been suspended between
> > kvm_check_and_clear_guest_paused() and is_softlockup(),
> > and jiffies (clock) thus shifted forward.
>
> Are jiffies really updated here?
I guess so. Why not?
VCPUs are not brought up simultaneously, it's up to the host that
schedules them. So, for instance, when we resume VCPU-3 and it
discovers this_cpu PVCLOCK_GUEST_STOPPED the VCPU-0 can already
be resumed, up and running, adding ticks to jiffies.
Am I missing the point of your question?
prev parent reply other threads:[~2021-05-20 5:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 14:06 [PATCH] watchdog: revert cleanup handling of false positives Sergey Senozhatsky
2021-05-18 15:36 ` Petr Mladek
2021-05-19 11:43 ` [PATCH] watchdog: Reliable handling of timestamps Petr Mladek
2021-05-19 12:01 ` Petr Mladek
2021-05-20 5:52 ` Sergey Senozhatsky
2021-05-20 5:29 ` Sergey Senozhatsky
2021-05-20 5:13 ` Sergey Senozhatsky [this message]
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