panic: mutex Giant owned at /tank/usr/src/sys/kern/kern_thread.c:357

[Marcel Moolenaar]

All,

We still have a ZFS-triggerable panic. The conditions under which the panic
happens are "simple":

1.  Create a mount-point /dos, and mount a MS-DOS file system
    there.
2.  Create directory /dos/zfs
3.  Make /boot/zfs a symlink to /dos/zfs
4.  create or import a pool, like "zpool import tank"

ZFS will create/update the zpool cache (/boot/zfs/zpool.cache)
and when done exits the zfskern/solthread thread, at which time
the panic happens:

panic: mutex Giant owned at /tank/usr/src/sys/kern/kern_thread.c:357
cpuid = 0
KDB: enter: panic
[thread pid 8 tid 100147 ]
Stopped at      kdb_enter+0x92: [I2]    addl r14=0xffffffffffe1f3f0,gp ;;
db> show alllocks
Process 8 (zfskern) thread 0xe000000010df4a20 (100147)
exclusive sleep mutex process lock (process lock) r = 0 (0xe000000010407660) locked @ /tank/usr/src/sys/kern/kern_kthread.c:326
exclusive sleep mutex Giant (Giant) r = 1 (0xe0000000048f8da8) locked @ /tank/usr/src/sys/kern/vfs_lookup.c:755

It looks to me that this is a bug in vfs_lookup.c, but I'm not
savvy enough to know this for sure or fix it fast myself. Help
is welcome, because this particular bug hits ia64 hard: /boot
is a symlink to /efi/boot, where /efi is a msdosfs mount point.

FYI,

-- 
Marcel Moolenaar
xcllnt at mac.com