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Date:      Fri, 11 Sep 2009 23:00:53 +0200
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Kris Kennaway <kris@FreeBSD.org>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>, Kip Macy <kmacy@FreeBSD.org>
Subject:   Re: panic: sx_xlock() of destroyed sx @	/zoo/kris/src8/sys/modules/zfs/../../cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_rlock.c:535
Message-ID:  <20090911210053.GA2090@garage.freebsd.pl>
In-Reply-To: <4AAA9187.2020907@FreeBSD.org>
References:  <4AA40E30.50109@FreeBSD.org> <4AAA9187.2020907@FreeBSD.org>

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On Fri, Sep 11, 2009 at 07:05:59PM +0100, Kris Kennaway wrote:
> Kris Kennaway wrote:
> >9.0 doing I/O to a zfs:
> >
> >panic: sx_xlock() of destroyed sx @=20
> >/zoo/kris/src8/sys/modules/zfs/../../cddl/contrib/opensolaris/uts/common=
/fs/zfs/zfs_rlock.c:535=20
> >
> >db> wh
> >Tracing pid 14 tid 100047 td 0xffffff000357c720
> >kdb_enter() at kdb_enter+0x3d
> >panic() at panic+0x17b
> >_sx_xlock() at _sx_xlock+0xe9
> >zfs_range_unlock() at zfs_range_unlock+0x38
> >zfs_get_data() at zfs_get_data+0xd7
> >zil_commit() at zil_commit+0x532
> >zfs_sync() at zfs_sync+0xa6
> >sync_fsync() at sync_fsync+0x13a
> >VOP_FSYNC_APV() at VOP_FSYNC_APV+0xb7
> >sync_vnode() at sync_vnode+0x157
> >sched_sync() at sched_sync+0x1d1
> >fork_exit() at fork_exit+0x12a
> >fork_trampoline() at fork_trampoline+0xe
> >--- trap 0, rip =3D 0, rsp =3D 0xffffff8125da0d30, rbp =3D 0 ---
> >
> >This was essentially just doing make world + cvs update + tar creation=
=20
> >in a loop and failed after about a week.
>=20
> Any ideas?  Machine is still in DDB.

I was trying to reproduce it by doing much more frequent syncs and
lowering vnodes limit, so they are inactivated more often, but I wasn't
able to reproduce it.

The problem here is that we lock a range for the given znode, but before
we unlock the range, znode is destroyed.

If you compile ZFS with debug (you have to uncomment CFLAGS+=3D-DDEBUG=3D1
in sys/modules/zfs/Makefile and recompile), we should be able to catch
who is killing the znode, because then, avl_destroy(&zp->z_range_avl)
should trigger a panic that tree isn't empty.

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

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