Re: Catching NForce2 lockup with NMI watchdog

[Mikael Pettersson]

Jesse Allen writes:
 > Hi,
 > 
 > I have a NForce2 board and can easily reproduce a lockup with grep on an IDE 
 > hard disk at UDMA 100.  The lockup occurs when both Local APIC + IO-APIC are 
 > enabled.  It was suggested to me to use NMI watchdog to catch it.  However, the 
 > NMI watchdog doesn't seem to work.
 > 
 > When I set the kernel parameter "nmi_watchdog=1" I get this message in 
 > /var/log/syslog:
 > Dec  4 20:10:30 tesore kernel: ..MP-BIOS bug: 8254 timer not connected to 
 > IO-APIC
 > Dec  4 20:10:30 tesore kernel: timer doesn't work through the IO-APIC - 
 > disabling NMI Watchdog!
 > 
 > "nmi_watchdog=2" seems to work at first, In /var/log/messages:
 > Dec  4 20:13:11 tesore kernel: testing NMI watchdog ... OK.
 > but it still locks up.

The NMI watchdog can only handle software lockups, since it relies on
the CPU, and for nmi_watchdog=1 the I/O-APIC + bus, still running.
Hardware lockups result in, well, hardware lockups :-(
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