>Number:         26407
>Category:       kern
>Synopsis:       panic while updating async mount option
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 23 00:09:00 UTC 2004
>Closed-Date:
>Last-Modified:
>Originator:     Ken Raeburn
>Release:        2.0 branch as of several days ago, maybe the 17th
>Organization:
MIT
>Environment:
alpha xp1000, everything rebuilt out of cvs after a 1.6 install; GENERIC kernel config
>Description:
I was running "top", a checkout of pkgsrc, and a build of the perl58-thread package from pkgsrc.  Out of curiousity for the difference it would make, I switched the "async" mount option on and off a few times while looking at the "top" output.

The last few lines of the slogin session:

   venix# mount -u -o noasync /usr
   venix# mount -u -o async /usr
   venix# mount -u -o noasync /usr
   sync

Since this is over a LAN, I assume from the lack of another prompt that it probably didn't finish the mount and didn't get to the "sync" command.

At this point, the kernel popped into the debugger:

panic: lockmgr: release of unlocked lock!

A traceback, quickly copied from the screen, includes:

panic
lockmgr
genfs_unlock
VOP_UNLOCK+0x3c
sched_sync+0x288
exception_return

I didn't get a crash dump.
>How-To-Repeat:
Repeatedly turn async on and off while doing lots of file system updates?

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: