----- Original Message ----- From: "Dan Mack" <m...@macktronics.com>
To: "Steven Hartland" <kill...@multiplay.co.uk>
Cc: <freebsd...@freebsd.org>; <freebsd-current@freebsd.org>; "Larry Rosenman" 
Sent: Monday, July 21, 2014 2:29 AM
Subject: Re: [ZFS][PANIC] Solaris Assert/zio.c:2548

On Mon, 21 Jul 2014, Steven Hartland wrote:

I just updated to I think 268921 earlier today and this is the first
time I've had a panic (HEAD-268921 that is)

I'll try to get some more data if I can get it back up and running.

That doesn't look like a related trace tbh.


After rebooting with a dumpdev; I got this :

kbd2 at ukbd0
Trying to mount root from zfs:tank []...
panic: deadlkres: possible deadlock detected for 0xfffff8000e089000, blocked 
for 1801216 ticks

cpuid = 6
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe085ef1d8d0
kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe085ef1d980
vpanic() at vpanic+0x126/frame 0xfffffe085ef1d9c0
panic() at panic+0x43/frame 0xfffffe085ef1da20
deadlkres() at deadlkres+0x35c/frame 0xfffffe085ef1da70
fork_exit() at fork_exit+0x84/frame 0xfffffe085ef1dab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe085ef1dab0
--- trap 0, rip = 0, rsp = 0xfffffe085ef1db70, rbp = 0 ---
KDB: enter: panic
[ thread pid 0 tid 100070 ]
Stopped at      kdb_enter+0x3e: movq    $0,kdb_why

I cannot seem to get past this yet so I'm open to suggestions.  I'm
still at the db> prompt if you'd like me to attempt to collect more

Just spotted an interesting message on a recent commit which may be

URL: http://svnweb.freebsd.org/changeset/base/268855
This specific commit makes boot hang just before mounting the root dataset for me when vfs.zfs.vdev.cache.size tunable is set. Unsetting this tunable or reverting this commit (currently running r268933 minus r268855) fixes the boot for me.

Please let me know if I can provide any more information.

- Nikolai Lifanov

The current code disables vdev caching by default so this will only
occur if manually enabled.

The code details the reason for this as:-
* TODO: Note that with the current ZFS code, it turns out that the
* vdev cache is not helpful, and in some cases actually harmful.  It
* is better if we disable this.  Once some time has passed, we should
* actually remove this to simplify the code.  For now we just disable
* it by setting the zfs_vdev_cache_size to zero.  Note that Solaris 11
* has made these same changes.


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