From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.active-venture.com ([67.228.131.205]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UPye5-0001qR-Ci for kexec@lists.infradead.org; Wed, 10 Apr 2013 17:17:17 +0000 Date: Wed, 10 Apr 2013 10:17:22 -0700 From: Guenter Roeck Subject: Re: [RFC PATCH] watchdog: Add hook for kicking in kdump path Message-ID: <20130410171722.GC19533@roeck-us.net> References: <1365192994-94850-1-git-send-email-dzickus@redhat.com> <516259D2.7000805@redhat.com> <20130408124858.GC79013@redhat.com> <20130408151509.GA20919@roeck-us.net> <20130409144431.GL79013@redhat.com> <20130409145228.GA1111@roeck-us.net> <20130409151423.GM79013@redhat.com> <20130409160757.GA27050@roeck-us.net> <20130410134039.GV79013@redhat.com> <20130410164914.GA18946@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20130410164914.GA18946@redhat.com> 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: David Teigland Cc: Don Zickus , linux-watchdog@vger.kernel.org, kexec@lists.infradead.org, LKML , wim@iguana.be, Dave Young , vgoyal@redhat.com On Wed, Apr 10, 2013 at 12:49:14PM -0400, David Teigland wrote: > On Wed, Apr 10, 2013 at 09:40:39AM -0400, Don Zickus wrote: > > However, we still have the problem that if the machine panics and we want > > to jump into the kdump kernel, we need to 'kick' the watchdog one more > > time. This provides us a sane sync point for determining how long we have > > to load the watchdog driver in the second kernel before the hardware > > reboots us. Otherwise the reboots are pretty random and nothing is > > guaranteed. > > Some time ago I submitted this patch > http://www.spinics.net/lists/linux-watchdog/msg01477.html > > to get rid of the one "extraneous" ping that was causing me trouble. > I'd still like to see merged, but haven't had time to follow up. > The use case makes sense to me, so it gets my Ack. Did Wim ever comment on it ? Thanks, Guenter > I have a use case where I need to guarantee that the watchdog > will *not* be pinged unless my userland daemon does the ping. > If my daemon is killed, the close() generates a ping that I > don't intend. This kdump ping looks like it would be another > instance that I'd need to suppress. Perhaps by renaming my flag > WDOG_NO_EXTRA_PING and checking it both in release and in > kick_for_kdump? > > (My daemon associates watchdog pings with shared storage heartbeats. > Based on the heartbeats, hosts in a cluster can calculate when an > unresponsive host last pinged its watchdog, and can be fairly > certain that the "dead" host has been reset by its watchdog 60 > seconds later. This is used as an alternative to i/o fencing > where we're protecting data on shared storage from corruption > after host failures. If there are uncontrolled watchdog pings, > then hosts don't know when a dead host might have last pinged > its watchdog, since it is no longer based on the last timestamp > it wrote to shared storage.) > > Dave > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec