On 08/02/2016 10:21 AM, Jens Axboe wrote:
> On 08/02/2016 06:58 AM, Jinpu Wang wrote:
>> Hi Jens,
>>
>> I found in blk_mq_register_disk, we blk_mq_disable_hotplug which in
>> turn mutex_lock(&all_q_mutex);
>> queue_for_each_hw_ctx(q, hctx, i) {
>> ret = blk_mq_register_hctx(hctx);
>> if (ret)
>> break; /// if about error out, we will call
>> unregister below
>> }
>>
>> if (ret)
>> blk_mq_unregister_disk(disk);
>>
>> In blk_mq_unregister_disk, we will try to disable_hotplug again, which
>> leads to dead lock.
>>
>> Did I miss anything?
>
> Nope, your analysis looks correct. This should fix it:
>
> http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=6316338a94b2319abe9d3790eb9cdc56ef81ac1a
Hi Jens,
Will that patch be included in stable kernels? I just encountered a
deadlock with kernel v4.7 that looks similar.
Thank you,
Bart.
INFO: task kworker/u64:6:136 blocked for more than 480 seconds.
Tainted: G W 4.7.0-dbg+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u64:6 D ffff88016f677bb0 0 136 2 0x00000000
Workqueue: events_unbound async_run_entry_fn
Call Trace:
[<ffffffff81622307>] schedule+0x37/0x90
[<ffffffff81622630>] schedule_preempt_disabled+0x10/0x20
[<ffffffff81624414>] mutex_lock_nested+0x144/0x350
[<ffffffff8130bbf2>] blk_mq_disable_hotplug+0x12/0x20
[<ffffffff8130d239>] blk_mq_register_disk+0x29/0x120
[<ffffffff81301bb6>] blk_register_queue+0xb6/0x160
[<ffffffff81310709>] add_disk+0x219/0x4a0
[<ffffffff8147def0>] sd_probe_async+0x100/0x1b0
[<ffffffff81088be5>] async_run_entry_fn+0x45/0x140
[<ffffffff8107f169>] process_one_work+0x1f9/0x6a0
[<ffffffff8107f659>] worker_thread+0x49/0x490
[<ffffffff81085e5a>] kthread+0xea/0x100
[<ffffffff81627f3f>] ret_from_fork+0x1f/0x40
3 locks held by kworker/u64:6/136:
#0: ("events_unbound"){.+.+.+}, at: [<ffffffff8107f0ea>]
process_one_work+0x17a/0x6a0
#1: ((&entry->work)){+.+.+.}, at: [<ffffffff8107f0ea>]
process_one_work+0x17a/0x6a0
#2: (all_q_mutex){+.+.+.}, at: [<ffffffff8130bbf2>]
blk_mq_disable_hotplug+0x12/0x20
INFO: task 02:8101 blocked for more than 480 seconds.
Tainted: G W 4.7.0-dbg+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
02 D ffff88039b747968 0 8101 1 0x00000004
Call Trace:
[<ffffffff81622307>] schedule+0x37/0x90
[<ffffffff81307aa1>] blk_mq_freeze_queue_wait+0x51/0xb0
[<ffffffff81309fca>] blk_mq_update_tag_set_depth+0x3a/0xb0
[<ffffffff8130a472>] blk_mq_init_allocated_queue+0x432/0x450
[<ffffffff8130a4c5>] blk_mq_init_queue+0x35/0x60
[<ffffffff814705b7>] scsi_mq_alloc_queue+0x17/0x50
[<ffffffff81471429>] scsi_alloc_sdev+0x2b9/0x350
[<ffffffff81471efb>] scsi_probe_and_add_lun+0x98b/0xe50
[<ffffffff81472eea>] __scsi_scan_target+0x5ca/0x6b0
[<ffffffff814730b1>] scsi_scan_target+0xe1/0xf0
[<ffffffffa0637856>] srp_create_target+0xf06/0x13d4 [ib_srp]
[<ffffffff8143a993>] dev_attr_store+0x13/0x20
[<ffffffff812599b0>] sysfs_kf_write+0x40/0x50
[<ffffffff81258d07>] kernfs_fop_write+0x137/0x1c0
[<ffffffff811d3933>] __vfs_write+0x23/0x140
[<ffffffff811d4b80>] vfs_write+0xb0/0x190
[<ffffffff811d5e54>] SyS_write+0x44/0xa0
[<ffffffff81627d25>] entry_SYSCALL_64_fastpath+0x18/0xa8
8 locks held by 02/8101:
#0: (sb_writers#4){.+.+.+}, at: [<ffffffff811d7b82>]
__sb_start_write+0xb2/0xf0
#1: (&of->mutex){+.+.+.}, at: [<ffffffff81258cd1>]
kernfs_fop_write+0x101/0x1c0
#2: (s_active#363){.+.+.+}, at: [<ffffffff81258cda>]
kernfs_fop_write+0x10a/0x1c0
#3: (&host->add_target_mutex){+.+.+.}, at: [<ffffffffa0636a84>]
srp_create_target+0x134/0x13d4 [ib_srp]
#4: (&shost->scan_mutex){+.+.+.}, at: [<ffffffff8147305d>]
scsi_scan_target+0x8d/0xf0
#5: (cpu_hotplug.lock){++++++}, at: [<ffffffff810624fd>]
get_online_cpus+0x2d/0x80
#6: (all_q_mutex){+.+.+.}, at: [<ffffffff8130a38a>]
blk_mq_init_allocated_queue+0x34a/0x450
#7: (&set->tag_list_lock){+.+...}, at: [<ffffffff8130a3ba>]
blk_mq_init_allocated_queue+0x37a/0x450
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