Re: Catching NForce2 lockup with NMI watchdog

[Mikael Pettersson]

Mike Fedyk writes:
 > On Fri, Dec 05, 2003 at 08:40:58AM +0100, Mikael Pettersson wrote:
 > > 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 :-(
 > 
 > But nmi_watchdog=1 is supposed to work with APIC, or IO-APIC, and it isn't
 > for his motherboard.  It doesn't increment NMI in /proc/interrupts.  And it
 > gives the above error message.  Isn't that a bug?

nmi_watchdog=1 only falls back to nmi_watchdog=2 if no SMP is detected.
If the I/O-APIC is detected but doesn't work, then the fallback
does not happen, and you need to set nmi_watchdog=2 explicitly.
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