NMI watchdog functionality on Freebsd

[Matthew Jacob]

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).