As seen here: http://groups-beta.google.com/group/mailing.freebsd.stable/browse_thread/thread/ad8029efaa6efe95/8f3269d6819ef0b8?lnk=st&q=panic+vm_pageout+fork_trampoline+fork_exit+freebsd+5.4&rnum=1&hl=en#8f3269d6819ef0b8 If you'd prefer, I can mail this to another list, in case stable isn't appropriate. We're seeing exactly the same panic here, with slight changes to the addresses referenced (phew, I don't have to transcribe it!) Our setup is: Dual Xeon 3.0Ghz 4 gigs of ram 3ware RAID10 (4 x 400GB) FreeBSD 5.4-RELEASE-p5 We're running a PAE kernel as well. The main difference between his kernel and ours is that we're not using acpi due to extremely poor network performance. Unfortunately the kernel will not dump core (even with a 16GB swap device). When I do a 'call doadump', it gives this error: Dumping 4608MB twa0: SCSI cmd=0x2a: ERROR (0x3: 0x0100): SGL entry contains zero data: address=0x0, length=0x10000, cmd=W The original panic line is: panic: lockmgr: thread 0xfffffff0, not exclusive lock holder c5f5fa80 unlocking Here's the lockmgr line from the panic: lockmgr(c61f5e14,6,c61f5d68,0,eb858a1c) lockmgr+0x421 lockmgr's 2nd argument was 6, LK_RELEASE, and lockmgr's 4th argument, the thread, was 0, so the panic was caused because a kernel thread was trying to release a lock for a non-kernel thread. Am I interpreting that correctly? 'show lockedvnods' reveals: 0xc61f5d68: tag devfs, type VCHR, usecount 4846, writecount 0, refcount 78, flags (VV_OBJBUF), lock type devfs: EXCL (count 1) by 0xc5f5fa80 (pid 8) dev da0s1a pid 8 is 'pagedaemon'. Any ideas/pointers? I've been going through the source and trying to figure out what's calling the lockmgr. I keep coming back to spec_write(), which doesn't appear to be used by any filesystems (unless it's used by procfs?)