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

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Message-ID: <20140116015045.GB3807@dhcp-16-126.nay.redhat.com>
Date:	Thu, 16 Jan 2014 09:50:45 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>, 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 01/15/14 at 11:46am, Vivek Goyal wrote:
> On Wed, Jan 15, 2014 at 09:11:42AM +0800, Dave Young wrote:
> 
> [..]
> > > I thought this problem was resolved (atleast conceptually) last time
> > > when Don Zickus brought it up.
> > > 
> > > He mentioned that it was concluded that keep watchdog interval long
> > > enough, say 60 seconds and keep on kicking it fast enough, say every
> > > 10-20 seconds. That would ensure that after the crash, there is atleast
> > > 60 - 20 = 40 seconds left before watchdog expires. And in that duration
> > > we should try to boot into second kernel load watchdog driver early enough
> > > from initramfs which can start kicking watchdog again.
> > 
> > Some drivers did stop the watchdog while module loading such as iTCO_wdt.
> 
> Instead of stopping why not keep on kicking it till user space takes
> over this job. This will also make sure that if kdump kernel hangs,
> watchdog wil do the job it is supposed to do?

Yes, rethinking about this problem, kicking it is better than stopping it.
But we will also have more uncertern time between userspace kicking before and
after panic.

Thanks
Dave
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