Fatal trap 12: page fault while in kernel mode/current process: 12 (swi2: cambio)

[Matthew Fleming]

> Since the last update and make world on Friday, 12th March I get a
crash
> on one of my FreeBSD SMP boxes (it is always the same core message),
> saying something about
> 
> Fatal trap 12: page fault while in kernel mode [...] current process:
12
> (swi2: cambio)

Can you show the stack traceback from the kernel core?

We had a problem a while ago at Isilon that I can't tell if it's
related.  In our case, the camisr() routine was called after panic(9)
started and before the halt of other processors.  This did Bad
Things(TM) since the mtx_lock is a no-op after panicstr is set.

We solved it locally by wrapping camisr() in a local cambio_swi()
routine that only called camisr(NULL) when panicstr == NULL.

Thanks,
matthew