Re: NMI not working as expected on Dell 2850

[christos%astron.com@localhost (Christos Zoulas)]

In article <m2lhjfwzav.fsf%athene.hamartun.priv.no@localhost>,
Tom Ivar Helbekkmo  <tih%hamartun.priv.no@localhost> wrote:
>I've been using the NMI button on the front of my old Dell PowerEdge
>2850 while debugging problems involving the amr and uhci drivers on it,
>and there's some problem with the handling of that button that I hope
>is something that can be fixed in the NetBSD kernel.
>
>I'm running NetBSD/amd64-current.
>
>In single CPU mode (boot -1), the NMI button will drop the machine into
>the debugger, but only once.  If I "continue" from the debugger, the NMI
>button will no longer work afterwards.

This sounds like the interrupt is masked and not cleared on exit.

>In SMP mode, the NMI button will, again, drop the machine into the
>debugger, but two of the CPUs will do so, the text announcing this being
>printed by both, and intermingled on the serial console.  Then, it seems
>that only one of them manages to grab the console for interactive use,
>because the debugger works just fine.  Backtraces for the various
>processors will show that two of them have gone through a trap(),
>kdb_trap(), printf() call sequence.  Which two will vary from time to
>time.  If I "continue" from the debugger, the machine will hang, and a
>forced power cycle is then the only way out.

This means that we are not stopping the other CPUs properly.

>Any hints as to how to figure out why this happens?

Don't know, but look at the code that masks and unmasks interrupts...

christos