From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1URqQk-0005xp-RG for kexec@lists.infradead.org; Mon, 15 Apr 2013 20:55:16 +0000 Date: Mon, 15 Apr 2013 16:55:04 -0400 From: Don Zickus Subject: Re: [RFC PATCH] watchdog: Add hook for kicking in kdump path Message-ID: <20130415205504.GQ79013@redhat.com> References: <20130409144431.GL79013@redhat.com> <20130409145228.GA1111@roeck-us.net> <20130409151423.GM79013@redhat.com> <20130409160757.GA27050@roeck-us.net> <20130410134039.GV79013@redhat.com> <20130410135123.GB15456@roeck-us.net> <20130410142055.GW79013@redhat.com> <20130410151041.GA6670@roeck-us.net> <20130412211627.GM79013@redhat.com> <20130412213024.GA5812@roeck-us.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20130412213024.GA5812@roeck-us.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=twosheds.infradead.org@lists.infradead.org To: Guenter Roeck Cc: linux-watchdog@vger.kernel.org, kexec@lists.infradead.org, LKML , wim@iguana.be, Dave Young , vgoyal@redhat.com On Fri, Apr 12, 2013 at 02:30:24PM -0700, Guenter Roeck wrote: > On Fri, Apr 12, 2013 at 05:16:27PM -0400, Don Zickus wrote: > > 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. > > > After looking into it again, I agree. Maybe you can give it a try. At least > other options look even more complicated (eg creating a watchdog class ?). I looked at the watchdog class in watchdog_core.c. Even implemented class_for_each_device. But got stuck trying to figure out how to go from a struct device *dev to a struct watchdog_device. Then I realized in the bowels of class_for_each_device were spinlocks. :-( So I implemented an RCU list. It isn't the prettiest solution but it seems to work. I posted a V2 and realized I forgot to cc you on it. I apologize for that. :-( I hope you can find it, otherwise I can post a pointer to it. Cheers, Don _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec