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Date:      Mon, 21 Jul 2014 03:54:56 +0100
From:      "Steven Hartland" <killing@multiplay.co.uk>
To:        "Dan Mack" <mack@macktronics.com>
Cc:        freebsd-fs@freebsd.org, freebsd-current@freebsd.org
Subject:   Re: [ZFS][PANIC] Solaris Assert/zio.c:2548
Message-ID:  <24B81F5E7779408AAA0F2D6CA3B16CED@multiplay.co.uk>
References:  <20140720140350.GA8498@borg.lerctr.org> <8D84B82C674B495DBF4951E0EE0D7117@multiplay.co.uk> <21dbecad27074fe34610bc587e6d0764@thebighonker.lerctr.org> <DE8C75117E794B8A83C7B2BAA417CD27@multiplay.co.uk> <E89CAE635D1E4BEDB421ABA5C04171E3@multiplay.co.uk> <05c8bccf4faf5005881fbd2b22f35428@thebighonker.lerctr.org> <4A0B8A1798484B3DB4DCD924A2DFEF22@multiplay.co.uk> <alpine.BSF.2.00.1407201851170.1604@olive.macktronics.com> <B66E77D31538477B97F651A91E84AF06@multiplay.co.uk> <alpine.BSF.2.00.1407202027200.1604@olive.macktronics.com>

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----- Original Message ----- 
From: "Dan Mack" <mack@macktronics.com>
To: "Steven Hartland" <killing@multiplay.co.uk>
Cc: <freebsd-fs@freebsd.org>; <freebsd-current@freebsd.org>; "Larry Rosenman" <ler@lerctr.org>
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.
>>
>>   Regards
>>   Steve
> 
> 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
> info.

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

> 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.

    Regards
    Steve




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