Re: [PATCH] check nmi watchdog is broken

[Mikael Pettersson <mikpe@csd.uu.se>]

Dave Jones writes:
 > My EM64T Dell Precision 470 seems to have problems both before
 > and after this change, though the behaviour changes.
 > 
 > With -rc3..
 > testing NMI watchdog ... CPU#1: NMI appears to be stuck (0)!
 > 
 > With -rc4...
 > Testing NMI watchdog ... CPU#4: NMI appears to be stuck (0)!
 > 
 > The CPU #'s are consistent across reboots (Ie, they're always the same).
 > Though the rc4 behaviour seems odd, as my CPUs are numbered 0-3.

There is known breakage in x86-64's nmi watchdog recently.
One of the problems is that the checking code inspects
all possible CPU numbers [0..NR_CPUS[ and not just the
ones actually present, which leads to false failure reports.

 > Bill (Cc'd) also reports that with -rc4, he sees around
 > a 10 second delay when it does that 'Testing NMI watchdog'
 > message.

And that's another of the known x86-64 breakages.

/Mikael