FreeBSD-9.1: machine reboots during snapshot creation, LORs found

[John Baldwin]

On Friday, May 31, 2013 8:26:11 am Andre Albsmeier wrote:
> Each day at 5:15 we are generating snapshots on various machines.
> This used to work perfectly under 7-STABLE for years but since
> we started to use 9.1-STABLE the machine reboots in about 10%
> of all cases.
> 
> After rebooting we find a new snapshot file which is a bit
> smaller than the good ones and with different permissions
> It does not succeed a fsck. In this example it is the one
> whose name is beginning with s3:
> 
> -r--r-----   1 root  operator  snapshot 72802894528 29 May 05:15 s2-2013.05.28-03.15.04
> -r--------   1 root  operator  snapshot 72802893824 29 May 05:15 s3-2013.05.29-03.15.03
> -r--r-----   1 root  operator  snapshot 72802894528 28 May 14:22 s4-2013.05.23-06.38.44
> -r--r-----   1 root  operator  snapshot 72802894528 28 May 14:22 s5-2013.05.24-03.15.03
> -r--r-----   1 root  operator  snapshot 72802894528 28 May 14:22 s6-2013.05.25-03.15.03
> 
> After enabling DIAGNOSTIC, WITNESS and INVARIANTS in the kernel
> I see the following LORs (mksnap_ffs starts exactly at 5:15):
> 
> May 29 05:15:00 <kern.crit> palveli kernel: lock order reversal:
> May 29 05:15:00 <kern.crit> palveli kernel: 1st 0xc2371da8 ufs (ufs) @ /src/src-9/sys/kern/vfs_mount.c:1240
> May 29 05:15:00 <kern.crit> palveli kernel: 2nd 0xc2371ec4 devfs (devfs) @ /src/src-9/sys/ufs/ffs/ffs_vfsops.c:1414
> May 29 05:15:04 <kern.crit> palveli kernel: lock order reversal:
> May 29 05:15:04 <kern.crit> palveli kernel: 1st 0xc228471c snaplk (snaplk) @ /src/src-9/sys/ufs/ufs/ufs_vnops.c:976
> May 29 05:15:04 <kern.crit> palveli kernel: 2nd 0xc22f25e4 ufs (ufs) @ /src/src-9/sys/ufs/ffs/ffs_snapshot.c:1626
> 
> Unfortunatley no corefiles are being generated ;-(.
> 
> I have checked and even rebuilt the (UFS1) fs in question
> from scratch. I have also seen this happen on an UFS2 on
> another machine and on a third one when running "dump -L"
> on a root fs.
> 
> Any hints of how to proceed?

Would it be possible to setup a serial console that is logged on this machine
to see if it is panic'ing but failing to write out a crashdump?

-- 
John Baldwin