Date: Tue, 18 Feb 2014 15:31:53 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-current@FreeBSD.org Subject: Re: panic: LK_RETRY set with incompatible flags (0x200400) or an error occured (11) Message-ID: <530360C9.9080609@FreeBSD.org> In-Reply-To: <20140218131815.GF3783@caravan.chchile.org> References: <20140210205607.GA3783@caravan.chchile.org> <52F94923.60102@FreeBSD.org> <20140211093529.GB3783@caravan.chchile.org> <20140214191858.GC3783@caravan.chchile.org> <52FF59B8.1080206@FreeBSD.org> <20140218131815.GF3783@caravan.chchile.org>
next in thread | previous in thread | raw e-mail | index | archive | help
on 18/02/2014 15:18 Jeremie Le Hen said the following:
> On Sat, Feb 15, 2014 at 02:12:40PM +0200, Andriy Gapon wrote:
>> on 14/02/2014 21:18 Jeremie Le Hen said the following:
>>> I've just got another occurence of the exact same panic. Any clue how
>>> to debug this?
>>
>> Could you please obtain *vp from frame 12 ?
>
> Sure:
>
> $1 = {v_tag = 0xffffffff815019a5 "zfs", v_op = 0xffffffff815164a0,
> v_data = 0xfffff80010dcb2e0, v_mount = 0xfffff80010dcd660,
> v_nmntvnodes = {tqe_next = 0xfffff80010dc7ce8,
> tqe_prev = 0xfffff80010dcd6c0}, v_un = {vu_mount = 0x0,
> vu_socket = 0x0, vu_cdev = 0x0, vu_fifoinfo = 0x0},
> v_hashlist = {le_next = 0x0, le_prev = 0x0}, v_cache_src = {
> lh_first = 0xfffff8005aeefcb0}, v_cache_dst = {tqh_first = 0x0,
> tqh_last = 0xfffff80010dc8050}, v_cache_dd = 0x0, v_lock = {
> lock_object = {lo_name = 0xffffffff815019a5 "zfs",
> lo_flags = 117112832, lo_data = 0, lo_witness = 0x0},
> lk_lock = 18446735277920538624, lk_exslpfail = 0, lk_timo = 51,
> lk_pri = 96}, v_interlock = {lock_object = {
> lo_name = 0xffffffff80b46085 "vnode interlock",
> lo_flags = 16973824, lo_data = 0, lo_witness = 0x0},
> mtx_lock = 4}, v_vnlock = 0xfffff80010dc8068, v_actfreelist = {
> tqe_next = 0x0, tqe_prev = 0xfffff80010dc7da8}, v_bufobj = {
> bo_lock = {lock_object = {
> lo_name = 0xffffffff80b4e613 "bufobj interlock",
> lo_flags = 86179840, lo_data = 0, lo_witness = 0x0},
> rw_lock = 1}, bo_ops = 0xffffffff80e2d440,
> bo_object = 0xfffff800a30bbd00, bo_synclist = {le_next = 0x0,
> le_prev = 0x0}, bo_private = 0xfffff80010dc8000,
> __bo_vnode = 0xfffff80010dc8000, bo_clean = {bv_hd = {
> tqh_first = 0x0, tqh_last = 0xfffff80010dc8120}, bv_root = {
> pt_root = 0}, bv_cnt = 0}, bo_dirty = {bv_hd = {
> tqh_first = 0x0, tqh_last = 0xfffff80010dc8140}, bv_root = {
> pt_root = 0}, bv_cnt = 0}, bo_numoutput = 0, bo_flag = 0,
> bo_bsize = 131072}, v_pollinfo = 0x0, v_label = 0x0,
> v_lockf = 0x0, v_rl = {rl_waiters = {tqh_first = 0x0,
> tqh_last = 0xfffff80010dc8188}, rl_currdep = 0x0},
> v_cstart = 0, v_lasta = 0, v_lastw = 0, v_clen = 0, v_holdcnt = 7,
> v_usecount = 6, v_iflag = 512, v_vflag = 1, v_writecount = 0,
> v_hash = 3, v_type = VDIR}
So, VV_ROOT is indeed set in v_vflag.
Thank you.
>> The problem seems to be happening in this piece of ZFS code:
>> if (cnp->cn_flags & ISDOTDOT) {
>> ltype = VOP_ISLOCKED(dvp);
>> VOP_UNLOCK(dvp, 0);
>> }
>> ZFS_EXIT(zfsvfs);
>> error = vn_lock(*vpp, cnp->cn_lkflags);
>> if (cnp->cn_flags & ISDOTDOT)
>> vn_lock(dvp, ltype | LK_RETRY);
>>
>> ltype is apparently LK_SHARED and the assertion is apparently triggered by
>> EDEADLK error. The error can occur only if a thread tries to obtain a lock in a
>> shared mode when it already has the lock exclusively.
>> My only explanation of how this could happen is that dvp == *vpp and cn_lkflags
>> is LK_EXCLUSIVE. In other words, this is a dot-dot lookup that results in the
>> same vnode. I think that this is only possible if dvp is the root vnode.
>> I am not sure if my theory is correct though.
>> Also, I am not sure if zfs_lookup() should be prepared to handle such a lookup
>> or if this kind of lookup should be handled by upper/other layers. In this case
>> these would be VFS lookup code and nullfs code.
>
--
Andriy Gapon
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?530360C9.9080609>