linux-kernel - RE: [PATCH 1/2] watchdog: introduce new watchdog AUTOSTART option

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Date:	Mon, 15 Apr 2013 02:13:46 +0000
From:	"Kim, Milo" <Milo.Kim@...com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	"wim@...ana.be" <wim@...ana.be>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] watchdog: introduce new watchdog AUTOSTART option

> -----Original Message-----
> From: Guenter Roeck [mailto:linux@...ck-us.net]
> Sent: Monday, April 15, 2013 11:07 AM
> To: Kim, Milo
> Cc: wim@...ana.be; linux-watchdog@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 1/2] watchdog: introduce new watchdog AUTOSTART
> option
> 
> On Mon, Apr 15, 2013 at 12:43:31AM +0000, Kim, Milo wrote:
> > Hi Guenter
> >
> > > I really don't like that idea. It defeats a significant part of the
> > > purpose
> > > for having a watchdog, which is to prevent user-space hangups.
> > >
> > > To make this a driver option is even more odd - it forces every
> user of
> > > this
> > > driver to use it in-kernel only, and makes /dev/watchdog quite
> useless.
> > >
> > > I mean, really, if you have such a watchdog, what is the point of
> using
> > > the
> > > watchdog infrastructure in the first place ? Just make it a kernel
> > > thread or
> > > timer-activated platform code which pings your watchdog once in a
> while.
> > > No
> > > need to get the watchdog infrastructure involved in the first place.
> > >
> > > Am I missing something ?
> >
> > I wanted to enable the watchdog timer without the watchdog
> application for
> > making sure the system alive.
> > However, I think I misunderstood the purpose of the watchdog driver.
> > The watchdog is for detecting user-space hangups rather than kernel
> stall.
> > Is it correct? If yes, this patch is totally wrong.
> >
> Correct. After all, if the kernel stalls, user space will stall as well,
> so by
> covering user space it covers both. Covering kernel alone doesn't help
> much,
> since most of the stalls (at least in my experience) happen in user
> space.

Got it. I nearly spoiled it due to my misunderstanding ;)
Many thanks!

Milo
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