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Date:      Fri, 25 Jan 2008 10:55:51 +0300
From:      Yar Tikhiy <yar@comp.chem.msu.su>
To:        Attilio Rao <attilio@freebsd.org>
Cc:        Kostik Belousov <kostikbel@gmail.com>, freebsd-current@freebsd.org
Subject:   Re: panic: System call lstat returning with 1 locks held
Message-ID:  <20080125075551.GB21633@comp.chem.msu.su>
In-Reply-To: <3bbf2fe10801240707o72b927cg74dbf9b7bbcd88fc@mail.gmail.com>
References:  <790a9fff0801150552l542a4238ofc12efe5fdb45fc2@mail.gmail.com> <20080115143924.GB57756@deviant.kiev.zoral.com.ua> <20080124122808.GA15600@freefall.freebsd.org> <3bbf2fe10801240518i6e18b2f5w84de652d4170c95b@mail.gmail.com> <20080124145811.GB78114@comp.chem.msu.su> <3bbf2fe10801240707o72b927cg74dbf9b7bbcd88fc@mail.gmail.com>

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On Thu, Jan 24, 2008 at 04:07:43PM +0100, Attilio Rao wrote:
> 2008/1/24, Yar Tikhiy <yar@comp.chem.msu.su>:
> > On Thu, Jan 24, 2008 at 02:18:56PM +0100, Attilio Rao wrote:
> > > 2008/1/24, Yar Tikhiy <yar@freebsd.org>:
> > > > On Tue, Jan 15, 2008 at 04:39:24PM +0200, Kostik Belousov wrote:
> > > > >
> > > > > I think this could be related to the recent vn_lock()/VOP_LOCK() KPI changes.
> > > > > Please, add DEBUG_VFS_LOCKS to the kernel config, and do the
> > > > >       show lockedvnods
> > > > > from the ddb prompt when the panic occurs. The witness does not track
> > > > > the lockmgr locks.
> > > >
> > > > I think I'm seeing the same panic on UFS.  It's rather nasty: I
> > > > cannot rebuild CURRENT natively due to it so I have to build it
> > > > under 6-STABLE.  My favourite way to trigger the panic reliably is
> > > > running `make install' in a simple port directory, e.g., portmaster,
> > > > but my system also panics during daily scripts run and, as already
> > > > said, if trying to build world.
> > >
> > > Yar,
> > > as it seems reproducible for you, can you please add this patch to the tree:
> > > http://www.freebsd.org/~attilio/debug_tdlocks.diff
> > >
> > > compile your kernel with:
> > > options KTR
> > > options KTR_COMPILE=(KTR_SPARE2)
> > > options KTR_MASK=(KTR_SPARE2)
> > > options KTR_ENTRIES=32768
> > >
> > > and once kernel panics, at ddb prompts do:
> > > > show ktr
> >
> > Thank you for your instant response!
> >
> > The patched kernel is already being built, but I've got the following
> > question in the meanwhile: Should I have updated my kernel to get your
> > latest changes to kern_lock.c?  Now my local copy of kern_lock.c is at
> > rev. 1.119, i.e., 1 revision behind today's change.
> 
> As long as this patch still applies, it should not any meaningful difference.
> 
> Thanks a lot for your effort of testing and reporting bugs!

I don't deserve these kind words because I disinformed you seriously.

My panic appears to be related not to UFS, but to NTFS.  Namely I
have an NTFS volume mounted read-only at /ntfs.  I have no idea why
the ports framework touches the /ntfs sub-tree, but not mounting
it in the first place makes the panic go away.  (I still wonder why
my system would also panic during buildworld, which should not touch
my /ntfs at all...  Now I'll try to do a buildworld w/o /ntfs mounted.)

At the same time, dismounting the NTFS volume leads to an instant
panic of a similar kind:

	panic: System call unmount returning with 5 locks held

More debug output is attached.

So at least UFS doesn't seem affected by the panic.  Excuse me for
my having provided wrong info.

-- 
Yar

panic: System call unmount returning with 5 locks held
cpuid = 0
KDB: enter: panic
[thread pid 985 tid 100085 ]
Stopped at      kdb_enter+0x3a: movl    $0,kdb_why
db> show lockedvn
Locked vnodes
db> sh ktr
678 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
677 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
676 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
675 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
674 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
673 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
672 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
671 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
670 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
669 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
668 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
667 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
666 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
665 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
664 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
663 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
662 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
661 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
660 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of -1 td_locks
659 (0xc37dd000:cpu0): _lockmgr: 0xc37dd000 bumping of 1 td_locks
db> where
Tracing pid 985 tid 100085 td 0xc37dd000
kdb_enter(c0b0c893,c0b0c893,c0b3ce37,d639cc8c,0,...) at kdb_enter+0x3a
panic(c0b3ce37,c0b2b59e,5,c0b2b59e,c0bbef10,...) at panic+0x12c
syscall(d639cd38) at syscall+0x46e
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (0, FreeBSD ELF32, nosys), eip = 0x280c4bbb, esp = 0xbfbfe59c, ebp = 0xbfbfe658 ---



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