On Mon, 2012-08-27 at 19:57 +0000, Mingarelli, Thomas wrote: > The main issue here is when an NMI comes in (which is hpwdt's main > focus...to source NMIs and then panic the box) and the system is > configured for kdump. We want the kdump to succeed and if the iLO > watchdog timer is left alone to keep running, the kdump will not > succeed. It will be interrupted by an ASR. This change ensures that > the iLO Watchdog timer is always stopped in the booting case (of any > kernel) or when an NMI arrives and we are in the process of taking a > kdump. And this change does not prevent running the watchdog daemon on the crash kernel, if we want to detect a hang condition on the crash kernel. The timer is re-enabled when /dev/watchdog is opened. The change only assures the timer is enabled when the daemon starts up. The timer running on the crash kernel without starting the daemon is a problem as it leads kdump to be interrupted. Thanks, -Toshi > > Tom > > -----Original Message----- > From: Lars Marowsky-Bree [mailto:lmb@xxxxxxxx] > Sent: Monday, August 27, 2012 2:22 PM > To: Kani, Toshimitsu; wim@xxxxxxxxx; linux-watchdog@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx; Mingarelli, Thomas; stable@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] hpwdt: Fix kdump issue in hpwdt > > On 2012-08-27T12:52:24, Toshi Kani <toshi.kani@xxxxxx> wrote: > > > kdump can be interrupted by watchdog timer when the timer is left > > activated on the crash kernel. Changed the hpwdt driver to disable > > watchdog timer at boot-time. This assures that watchdog timer is > > disabled until /dev/watchdog is opened, and prevents watchdog timer > > to be left running on the crash kernel. > > How does this protect against the system hanging again in the crash > kernel, or possibly hardware caches to flush more data to shared > storage? > > (I'm asking from the perspective of the hpwdt being used as a fencing > mechanism in a cluster setting.) > > Or is the argument that it's "very unlikely" that a system in such a > state would not make it far enough into the crash kernel? > > > Regards, > Lars > -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
