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

[Kevin Oberman]

> Date: Mon, 12 Jul 2004 22:56:12 +0200
> From: Johan Pettersson <manlix at demonized.net>
> Sender: owner-freebsd-current at freebsd.org
> 
> > 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.

I have found the interrupt latency on a loaded system to be simply
unacceptable and have backed off the code to before this change wa made.

I am running:
 sys/sys/interrupt.h          - v1.27
 sys/kern/kern_intr.c         - v1.110
 sys/i386/i386/intr_machdep.c - v1.6
 sys/kern/sched_ule.c         - v1.109
and this has things back to normal. thanks to Ariff Abdullah for the
list of file versions.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634