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

[Andre Albsmeier]

On Mon, 17-Jun-2013 at 21:30:31 +0200, John Baldwin wrote:
> On Sunday, June 16, 2013 2:39:42 am Andre Albsmeier wrote:
> > On Fri, 31-May-2013 at 16:51:03 +0200, John Baldwin wrote:
> > > 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?
> > 
> > Couldn't attach the serial console yet ;-(. But I had people
> > attach a KVMoverIP switch and enabled the various KDB options
> > in the kernel. Now we can see a bit more (see below) -- no
> > crashdump is being generated though.
> 
> :(  Unfortunately these LORs don't really help with discerning the cause of
> the reboot.  If you have remote power access (and still wanted to test this)
> one option would be to change KDB to drop into the debugger on a panic.
> Then you could connect over the KVM and take images of the original panic
> along with a stack trace.

After making core dumps work actually (dump device was stopped and
FreeBSD-9 doesn't start it automatically) and upgrading to a recent
version of 9.1-STABLE it _seems_ that the troubles are gone. In case
the problem reappears I'll come back ;-).

Thanks,

	-Andre

> 
> -- 
> John Baldwin

-- 
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