Re: Bug 4.1.16: self-detected stall in net/unix/?
From: Rainer Weikusat
Date: Thu Feb 11 2016 - 10:56:28 EST
Philipp Hahn <pmhahn@xxxxxxxxx> writes:
[...]
> Probably the same bug was also reported to samba-technical by Karolin
> Seeger; she filed the bug for 3.19-ckt with Ubuntu:
>
> <https://bugs.launchpad.net/ubuntu/+source/linux-lts-trusty/+bug/1543980>
>
> Running the Samba test suite reproduces the problem; see bug for
> details.
JFTR: The oops in this bug report is for 3.13.0-77 and the patch you
reverted for 4.1 is not part of that (at least not of the upstream 3.13).
[...]
>> [ 598.492559] =====================================
>> [ 598.502646] [ BUG: bad unlock balance detected! ]
>> [ 598.512874] 4.1.16+ #24 Not tainted
>> [ 598.523134] -------------------------------------
>> [ 598.533592] smbd/8659 is trying to release lock (&(&u->lock)->rlock) at:
>> [ 598.544429] [<ffffffff815d1319>] spin_unlock+0x9/0x10
>> [ 598.555148] but there are no more locks to release!
>> [ 598.565892]
>> [ 598.565892] other info that might help us debug this:
>> [ 598.586936] no locks held by smbd/8659.
>> [ 598.597478]
>> [ 598.597478] stack backtrace:
>> [ 598.618275] CPU: 3 PID: 8659 Comm: smbd Not tainted 4.1.16+ #24
>> [ 598.628820] Hardware name: System manufacturer System Product Name/P7F-X Series, BIOS 0703 09/24/2010
>> [ 598.650020] ffffffff815d1319 ffff8800b8efbb88 ffffffff8163ee73 0000000000000000
>> [ 598.661051] ffff880034fc4110 ffff8800b8efbbb8 ffffffff810db540 ffff880034fc4110
>> [ 598.671990] ffff880034fc4110 ffff88023206bd40 ffffffff815d1319 ffff8800b8efbc08
>> [ 598.682736] Call Trace:
>> [ 598.693187] [<ffffffff815d1319>] ? spin_unlock+0x9/0x10
>> [ 598.703798] [<ffffffff8163ee73>] dump_stack+0x4c/0x65
>> [ 598.714223] [<ffffffff810db540>] print_unlock_imbalance_bug+0x100/0x110
>> [ 598.724611] [<ffffffff815d1319>] ? spin_unlock+0x9/0x10
>> [ 598.734763] [<ffffffff810e0d8e>] lock_release+0x2be/0x430
>> [ 598.744636] [<ffffffff81648303>] _raw_spin_unlock+0x23/0x40
>> [ 598.754230] [<ffffffff815d41a8>] ? unix_dgram_sendmsg+0x288/0x6f0
>> [ 598.763840] [<ffffffff815d1319>] spin_unlock+0x9/0x10
>> [ 598.773126] [<ffffffff815d41e7>] unix_dgram_sendmsg+0x2c7/0x6f0
>> [ 598.782209] [<ffffffff814f6c9d>] sock_sendmsg+0x4d/0x60
>> [ 598.791313] [<ffffffff814f7c3b>] ___sys_sendmsg+0x2db/0x2f0
>> [ 598.800369] [<ffffffff812083c8>] ? kmem_cache_free+0x328/0x360
>> [ 598.809383] [<ffffffff8127c1c0>] ? locks_free_lock+0x50/0x60
>> [ 598.818157] [<ffffffff814f8649>] __sys_sendmsg+0x49/0x90
>> [ 598.826742] [<ffffffff814f86a2>] SyS_sendmsg+0x12/0x20
>> [ 598.835110] [<ffffffff816486f2>] system_call_fastpath+0x16/0x7a
>> [ 598.843546] ------------[ cut here ]------------
>> [ 598.851999] WARNING: CPU: 3 PID: 8659 at net/core/skbuff.c:691 skb_release_head_state+0xaa/0xb0()
Could you send your disassembled unix_dgram_sendmsg (objdump -d)? This
would be enormously helpful wrt determining which unlock is involved
here.