linux-kernel - Re: [PATCH] kernel/watchdog: fix spurious hard lockups

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Message-ID: <20170628114058.GB5234@dhcp22.suse.cz>
Date:   Wed, 28 Jun 2017 13:40:59 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     kan.liang@...el.com
Cc:     linux-kernel@...r.kernel.org, dzickus@...hat.com, mingo@...nel.org,
        akpm@...ux-foundation.org, babu.moger@...cle.com,
        atomlin@...hat.com, prarit@...hat.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        tglx@...utronix.de, eranian@...gle.com, acme@...hat.com,
        ak@...ux.intel.com, stable@...r.kernel.org
Subject: Re: [PATCH] kernel/watchdog: fix spurious hard lockups

On Tue 20-06-17 14:33:09, kan.liang@...el.com wrote:
> From: Kan Liang <Kan.liang@...el.com>
> 
> Some users reported spurious NMI watchdog timeouts.
> 
> We now have more and more systems where the Turbo range is wide enough
> that the NMI watchdog expires faster than the soft watchdog timer that
> updates the interrupt tick the NMI watchdog relies on.

AFAIR the watchdog doesn't rely on deferred timers so this would suggest
that a standard hrtimer can expire much later than programmed, right?
If that is the case how come other parts of the system do not break. We
do rely on hrtimers on many other places?
-- 
Michal Hocko
SUSE Labs