Date: Wed, 23 Jan 2013 08:47:41 -0800 From: Matthew Jacob <mjacob@freebsd.org> To: freebsd-hackers@freebsd.org Subject: Re: NMI watchdog functionality on Freebsd Message-ID: <5100142D.7040904@freebsd.org> In-Reply-To: <201301231025.41118.jhb@freebsd.org> References: <1358894455.17521.YahooMailClassic@web181706.mail.ne1.yahoo.com> <201301231025.41118.jhb@freebsd.org>
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On 1/23/2013 7:25 AM, John Baldwin wrote: > On Tuesday, January 22, 2013 5:40:55 pm Sushanth Rai wrote: >> Hi, >> >> Does freebsd have some functionality similar to Linux's NMI watchdog ? I'm > aware of ichwd driver, but that depends to WDT to be available in the > hardware. Even when it is available, BIOS needs to support a mechanism to > trigger a OS level recovery to get any useful information when system is > really wedged (with interrupt disabled) The principle purpose of a watchdog is to keep the system from hanging. Information is secondary. The ichwd driver can use the LPC part of ICH hardware that's been there since ICH version 4. I implemented this more fully at Panasas. The first importance is to keep the system from being hung. The next piece of information is to detect, on reboot, that a watchdog event occurred. Finally, trying to isolate why is good. This is equivalent to the tco_WDT stuff on Linux. It's not interrupt driven (it drives the reset line on the processor).
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