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Date: Wed, 15 Sep 2004 11:27:27 -0400 (EDT)
From: Robert Watson <rwatson@FreeBSD.org>
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Subject: Re: Possible NULL pointer deref in sched_add() via maybe_preempt()
	and	kse_release()
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On Wed, 15 Sep 2004, Robert Watson wrote:

> The source code here is probably about a day old; the panic occurred
> during a kernel build using an NFS-mounted source tree and local object
> tree.  MySQL should have been basically idle, since no clients were
> active or had been active recently, but no doubt it wakes up once in a
> while to do something. 

Just to follow up now the disks have fsck'd.  The kernel source was fairly
up-to-date with regards to recent threading and scheduling changes.  The
file revisions of interest appear to be:

  File           My Revision     CVS Revision
  sched_4bsd.c   1.64            1.64
 *kern_switch.c  1.91            1.92 (but only change is a ULE change?)
  kern_kse.c     1.200           1.200
  kern_thread.c  1.196           1.196
  kern_intr.c    1.115           1.115

I was able to get a core dump, but in the new world order I can no longer
use NIS, so it will take me a few minutes to get something useful out of
it.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Principal Research Scientist, McAfee Research