linux-kernel - Re: [PATCH v3] watchdog: Add hook for kicking in kdump path

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Message-ID: <87li8gaku0.fsf@xmission.com>
Date:	Wed, 17 Apr 2013 14:49:59 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Don Zickus <dzickus@...hat.com>
Cc:	linux-watchdog@...r.kernel.org, kexec@...ts.infradead.org,
	wim@...ana.be, LKML <linux-kernel@...r.kernel.org>,
	vgoyal@...hat.com, dyoung@...hat.com, linux@...ck-us.net
Subject: Re: [PATCH v3] watchdog: Add hook for kicking in kdump path

Don Zickus <dzickus@...hat.com> writes:

> A common problem with kdump is that during the boot up of the
> second kernel, the hardware watchdog times out and reboots the
> machine before a vmcore can be captured.
>
> Instead of tellling customers to disable their hardware watchdog
> timers, I hacked up a hook to put in the kdump path that provides
> one last kick before jumping into the second kernel.
>
> The assumption is the watchdog timeout is at least 10-30 seconds
> long, enough to get the second kernel to userspace to kick the watchdog
> again, if needed.

Why not double the watchdog timeout? and/or pet the watchdog a little
more frequently.

This is the least icky hook I have seen proposed to be put on the kexec
on panic path, but I still suspect this may reduce the ability to take a
crash dump.  What happens if it was the watchdog timer that panic'd for
example.

Eric
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