Native preemption is the culprit [was Re: today's CURRENT lockups]

[Johan Pettersson]

> It's not currently clear what the cause is -- reports suggest that
> it's an existing bug that's getting triggered by preemption, although
> I wouldn't rule out a bug in the preemption implementation itself. 
> I'm currently setting up a box with NMI to see if I can get some more
> useful information, as serial break isn't cutting it (suggesting a
> leaked spin lock or critical section).  I don't have an ETA, but I'm
> guessing that we'll have some sort of resolution in the next day or
> two.  If not, I guess we back out the change, or disable PREEMPTION by
> default.
> 
> Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
> robert at fledge.watson.org      Principal Research Scientist, McAfee
> Research
> 

Okey... Im going to build a kernel with #define PREEMPTION disabled now.
Its too annoying to get lock-ups all the time. :) Shout when you have
some code to be tested.