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

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Date:	Fri, 12 Apr 2013 17:16:27 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Dave Young <dyoung@...hat.com>, linux-watchdog@...r.kernel.org,
	kexec@...ts.infradead.org, wim@...ana.be,
	LKML <linux-kernel@...r.kernel.org>, vgoyal@...hat.com
Subject: Re: [RFC PATCH] watchdog: Add hook for kicking in kdump path

On Wed, Apr 10, 2013 at 08:10:41AM -0700, Guenter Roeck wrote:
> > have no idea how to even find out if multiple watchdogs are open on the
> > system.  Is there a list I could walk?  And with regard to 'watchdog is
> 
> /* the dev_t structure to store the dynamically allocated watchdog devices */
> static dev_t watchdog_devt;
> 
> One way to look up the allocated watchdogs might be to loop through all kobj
> instances for the major device using kobj_lookup. Don't know if there is a
> better way.

Hmm, I got around to poking at this today and I am not sure kobj_lookup
will work.  Besides being surrounded with another mutex, I don't have
access to the character device domain to pass to kobj_lookup.

Perhaps I am not reading the code right, but I can't find a good way
forward.

The only other hack I can think of, is to embed a list object in the
watchdog structure and list_add each new register'd watchdog.  Then it
would be trivial to walk the watchdog list.

Thoughts?

Cheers,
Don

> 
> > running', I thought 'watchdog_active' would do that.  But again, I could
> > be misreading the code.
> > 
> You are right. Missed that part, sorry.
> 
> Guenter
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