Re: iouring locking issue in io_req_complete_post() / io_rsrc_node_ref_zero()

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On 8/9/21 4:01 PM, Nadav Amit wrote:
> 
>> On Aug 9, 2021, at 6:49 AM, Jens Axboe <axboe@xxxxxxxxx> wrote:
>>
>> On 8/8/21 10:36 PM, Nadav Amit wrote:
>>> Jens, others,
>>>
>>> Sorry for bothering again, but I encountered a lockdep assertion failure:
>>>
>>> [  106.009878] ------------[ cut here ]------------
>>> [  106.012487] WARNING: CPU: 2 PID: 1777 at kernel/softirq.c:364 __local_bh_enable_ip+0xaa/0xe0
>>> [  106.014524] Modules linked in:
>>> [  106.015174] CPU: 2 PID: 1777 Comm: umem Not tainted 5.13.1+ #161
>>> [  106.016653] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/22/2020
>>> [  106.018959] RIP: 0010:__local_bh_enable_ip+0xaa/0xe0
>>> [  106.020344] Code: a9 00 ff ff 00 74 38 65 ff 0d a2 21 8c 7a e8 ed 1a 20 00 fb 66 0f 1f 44 00 00 5b 41 5c 5d c3 65 8b 05 e6 2d 8c 7a 85 c0 75 9a <0f> 0b eb 96 e8 2d 1f 20 00 eb a5 4c 89 e7 e8 73 4f 0c 00 eb ae 65
>>> [  106.026258] RSP: 0018:ffff88812e58fcc8 EFLAGS: 00010046
>>> [  106.028143] RAX: 0000000000000000 RBX: 0000000000000201 RCX: dffffc0000000000
>>> [  106.029626] RDX: 0000000000000007 RSI: 0000000000000201 RDI: ffffffff8898c5ac
>>> [  106.031340] RBP: ffff88812e58fcd8 R08: ffffffff8575dbbf R09: ffffed1028ef14f9
>>> [  106.032938] R10: ffff88814778a7c3 R11: ffffed1028ef14f8 R12: ffffffff85c9e9ae
>>> [  106.034363] R13: ffff88814778a000 R14: ffff88814778a7b0 R15: ffff8881086db890
>>> [  106.036115] FS:  00007fbcfee17700(0000) GS:ffff8881e0300000(0000) knlGS:0000000000000000
>>> [  106.037855] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [  106.039010] CR2: 000000c0402a5008 CR3: 000000011c1ac003 CR4: 00000000003706e0
>>> [  106.040453] Call Trace:
>>> [  106.041245]  _raw_spin_unlock_bh+0x31/0x40
>>> [  106.042543]  io_rsrc_node_ref_zero+0x13e/0x190
>>> [  106.043471]  io_dismantle_req+0x215/0x220
>>> [  106.044297]  io_req_complete_post+0x1b8/0x720
>>> [  106.045456]  __io_complete_rw.isra.0+0x16b/0x1f0
>>> [  106.046593]  io_complete_rw+0x10/0x20
>>>
>>> [ .... The rest of the call-stack is my stuff ] 
>>>
>>>
>>> Apparently, io_req_complete_post() disables IRQs and this code-path seems
>>> valid (IOW: I did not somehow cause this failure). I am not familiar with
>>> this code, so some feedback would be appreciated.
>>
>> Can you try with this patch?
> 
> Thanks! I might have hit another issue, but apparently even if it is
> real, it is unrelated.
> 
> Tested-by: Nadav Amit <nadav.amit@xxxxxxxxx>

Thanks for testing! And regarding another issue, I would expect nothing
less :-). It's always interesting to see new paths being paved, and
inevitably that'll shake out a few issues in code that's been less
exercised than the general part.

-- 
Jens Axboe




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