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Date:      Wed, 19 Oct 2016 14:31:48 -0700
From:      Alfred Perlstein <bright@mu.org>
To:        Poul-Henning Kamp <phk@phk.freebsd.dk>, Andriy Gapon <avg@FreeBSD.org>
Cc:        freebsd-arch@FreeBSD.org
Subject:   Re: watchdog end-user interface
Message-ID:  <126689b6-c44b-688f-faff-4a27d3bd29b8@mu.org>
In-Reply-To: <21377.1476875898@critter.freebsd.dk>
References:  <ec3dfab5-c3bc-e9e5-181e-8c2704f60acd@FreeBSD.org> <21377.1476875898@critter.freebsd.dk>

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On 10/19/16 4:18 AM, Poul-Henning Kamp wrote:
> --------
> In message <ec3dfab5-c3bc-e9e5-181e-8c2704f60acd@FreeBSD.org>, Andriy Gapon wri
> tes:
>
>> I want to question if those options really belong to watchdogd.
>> When a watchdog timer expires that results in a system-wide action (like a
>> system reset).  To me, that implies that there should be a single system-wide
>> configuration point.  And I am not sure that the daemon is the best choice for it.
> The reason I originally put it in a daemon, was to have the watchdog
> implicitly test the kernels ability to schedule trivial processes.
>
> It used to be, and may still be so that, there are deadlocks where
> the kernel was twiddling its thumbs but userland did not progress.
> Typical triggers for this are disk-I/O errors, corrupt filesystems,
> memory overcommit etc.
>
> A kernel-only watchdog patter would not trigger in that case.
Exactly.

-Alfred




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