Date: Thu, 31 Dec 2009 08:49:07 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Marcel Moolenaar <xcllnt@mac.com> Subject: Re: panic: mutex Giant owned at /tank/usr/src/sys/kern/kern_thread.c:357 Message-ID: <200912310849.07829.jhb@freebsd.org> In-Reply-To: <4C83129A-00FE-4E93-8F65-BFAE4B6F6BC7@mac.com> References: <4C83129A-00FE-4E93-8F65-BFAE4B6F6BC7@mac.com>
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On Wednesday 30 December 2009 4:55:44 pm Marcel Moolenaar wrote: > 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. Can you get a stack trace? The bug is probably that ZFS isn't properly honoring NDHASGIANT() someplace. Hmm, it certainly doesn't honor it in lookupnameat(). You could maybe have it unlock Giant there, but I believe that will result in ZFS not acquiring Giant for any vnode operations on a returned vnode from a !MPSAFE filesystem. -- John Baldwin
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