linux-kernel - Re: [PATCH] watchdog: add a parameter for stop wdt before register

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Message-ID: <20140115165512.GD3180@redhat.com>
Date:	Wed, 15 Jan 2014 11:55:12 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	Dave Young <dyoung@...hat.com>, wim@...ana.be, dzickus@...hat.com,
	bhe@...hat.com, linux-watchdog@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: add a parameter for stop wdt before register

On Wed, Jan 15, 2014 at 12:15:56PM +0000, One Thousand Gnomes wrote:
> > watchdog and crash dump really conflicts to some degree, from the watchdog
> > point of view it can reboot system whhen kdump kernel hangs. But from kdump
> > point of view it want ensure saving the vmcore for later debugging.
> > 
> > Maybe we can only select only one in this case.
> 
> You want to be able to make a decision at runtime which to use.
> 
> > > - if it can be stopped, you can open and stop it
> > 
> > For the last one since crashing happens we have no chance to open and stop.
> 
> When you decide you need to set up to catch a core rather than just
> crash you can open and stop the watchdog (if supported), and you can then
> set up for a kdump and then at some point later if it crashes capture the
> dump.

Disabling watchdog if kdump serice starts will not make many happy. If
kernel hangs, we don't have a functionality to reboot it.

What about other idea of keeping watchdog interval long enough that new
kernel can boot, driver can load and then new driver/user space can
continue to kick the watchdog. And if second kernel hangs, watchdog will
reboot the system.

Thanks
Vivek
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