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From: ebiederm@xmission.com (Eric W. Biederman)
To: Don Zickus <dzickus@redhat.com>
Cc: linux-watchdog@vger.kernel.org, kexec@lists.infradead.org,
	LKML <linux-kernel@vger.kernel.org>,
	wim@iguana.be, linux@roeck-us.net, dyoung@redhat.com,
	vgoyal@redhat.com
Subject: Re: [PATCH v3] watchdog: Add hook for kicking in kdump path
Date: Wed, 17 Apr 2013 14:49:59 -0700	[thread overview]
Message-ID: <87li8gaku0.fsf@xmission.com> (raw)
In-Reply-To: <1366233596-34681-1-git-send-email-dzickus@redhat.com> (Don Zickus's message of "Wed, 17 Apr 2013 17:19:56 -0400")

Don Zickus <dzickus@redhat.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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WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman)
To: Don Zickus <dzickus@redhat.com>
Cc: linux-watchdog@vger.kernel.org, kexec@lists.infradead.org,
	wim@iguana.be, LKML <linux-kernel@vger.kernel.org>,
	vgoyal@redhat.com, dyoung@redhat.com, linux@roeck-us.net
Subject: Re: [PATCH v3] watchdog: Add hook for kicking in kdump path
Date: Wed, 17 Apr 2013 14:49:59 -0700	[thread overview]
Message-ID: <87li8gaku0.fsf@xmission.com> (raw)
In-Reply-To: <1366233596-34681-1-git-send-email-dzickus@redhat.com> (Don Zickus's message of "Wed, 17 Apr 2013 17:19:56 -0400")

Don Zickus <dzickus@redhat.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

  parent reply	other threads:[~2013-04-17 21:50 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-17 21:19 [PATCH v3] watchdog: Add hook for kicking in kdump path Don Zickus
2013-04-17 21:19 ` Don Zickus
2013-04-17 21:33 ` Guenter Roeck
2013-04-17 21:33   ` Guenter Roeck
2013-04-17 21:49 ` Eric W. Biederman [this message]
2013-04-17 21:49   ` Eric W. Biederman
2013-04-18  3:03   ` Guenter Roeck
2013-04-18  3:03     ` Guenter Roeck
2013-04-18 13:00   ` Don Zickus
2013-04-18 13:00     ` Don Zickus
2013-04-18 13:49     ` Guenter Roeck
2013-04-18 13:49       ` Guenter Roeck
2013-04-18 13:52       ` Don Zickus
2013-04-18 13:52         ` Don Zickus
2013-04-18 14:54         ` Guenter Roeck
2013-04-18 14:54           ` Guenter Roeck
2013-04-24 14:42           ` Don Zickus
2013-04-24 14:42             ` Don Zickus
2013-04-24 15:21             ` Guenter Roeck
2013-04-24 15:21               ` Guenter Roeck
2013-05-27 19:16               ` Wim Van Sebroeck
2013-05-28  1:10                 ` Guenter Roeck
2013-05-28  1:10                   ` Guenter Roeck
2013-05-30 20:37                   ` Wim Van Sebroeck
2013-05-28 15:34                 ` Guenter Roeck
2013-05-28 15:34                   ` Guenter Roeck
2013-05-30 21:54                   ` Wim Van Sebroeck
2013-04-18 16:35 ` Eric W. Biederman
2013-04-18 16:35   ` Eric W. Biederman
2013-04-18 17:44   ` Don Zickus
2013-04-18 17:44     ` Don Zickus
2013-04-18 18:09     ` Eric W. Biederman
2013-04-18 18:09       ` Eric W. Biederman

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