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Subject: Re: linux 4.19.19: md0_raid:1317 blocked for more than 120 seconds.
To:     Wolfgang Walter <linux@stwm.de>
Cc:     Jens Axboe <axboe@kernel.dk>, NeilBrown <neilb@suse.com>,
        linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org
References: <2131016.q2kFhguZXe@stwm.de>
 <0ee180ac-bb43-6c2f-4084-5cc452a18c9d@suse.com> <3057098.nBgIypvgED@stwm.de>
From:   Guoqing Jiang <gqjiang@suse.com>
Message-ID: <0c832f67-de10-8872-d3db-6a9f11c97454@suse.com>
Date:   Thu, 14 Feb 2019 10:09:56 +0800
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On 2/12/19 7:20 PM, Wolfgang Walter wrote:
> Am Dienstag, 12. Februar 2019, 16:20:11 schrieb Guoqing Jiang:
>> On 2/11/19 11:12 PM, Wolfgang Walter wrote:
>>> With 4.19.19 we see sometimes the following issue (practically only with
>>> blk_mq, though):
>>>
>>> Feb  4 20:04:46 tettnang kernel: [252300.060165] INFO: task md0_raid1:317
>>> blocked for more than 120 seconds. Feb  4 20:04:46 tettnang kernel:
>>> [252300.060188]       Not tainted 4.19.19-debian64.all+1.1 #1 Feb  4
>>> 20:04:46 tettnang kernel: [252300.060197] "echo 0 >
>>> /proc/sys/kernel/hung_task_timeout_secs" disables this message. Feb  4
>>> 20:04:46 tettnang kernel: [252300.060207] md0_raid1       D    0   317
>>>    2 0x80000000 Feb  4 20:04:46 tettnang kernel: [252300.060211] Call
>>> Trace:
>>> Feb  4 20:04:46 tettnang kernel: [252300.060222]  ? __schedule+0x2a2/0x8c0
>>> Feb  4 20:04:46 tettnang kernel: [252300.060226]  ?
>>> _raw_spin_unlock_irqrestore+0x20/0x40 Feb  4 20:04:46 tettnang kernel:
>>> [252300.060229]  schedule+0x32/0x90 Feb  4 20:04:46 tettnang kernel:
>>> [252300.060241]  md_super_wait+0x69/0xa0 [md_mod] Feb  4 20:04:46
>>> tettnang kernel: [252300.060247]  ? finish_wait+0x80/0x80 Feb  4 20:04:46
>>> tettnang kernel: [252300.060255]  md_bitmap_wait_writes+0x8e/0xa0
>>> [md_mod] Feb  4 20:04:46 tettnang kernel: [252300.060263]  ?
>>> md_bitmap_get_counter+0x42/0xd0 [md_mod] Feb  4 20:04:46 tettnang kernel:
>>> [252300.060271]  md_bitmap_daemon_work+0x1e8/0x380 [md_mod] Feb  4
>>> 20:04:46 tettnang kernel: [252300.060278]  ? md_rdev_init+0xb0/0xb0
>>> [md_mod] Feb  4 20:04:46 tettnang kernel: [252300.060285]
>>> md_check_recovery+0x26/0x540 [md_mod] Feb  4 20:04:46 tettnang kernel:
>>> [252300.060290]  raid1d+0x5c/0xf00 [raid1] Feb  4 20:04:46 tettnang
>>> kernel: [252300.060294]  ? preempt_count_add+0x79/0xb0 Feb  4 20:04:46
>>> tettnang kernel: [252300.060298]  ? lock_timer_base+0x67/0x80 Feb  4
>>> 20:04:46 tettnang kernel: [252300.060302]  ?
>>> _raw_spin_unlock_irqrestore+0x20/0x40 Feb  4 20:04:46 tettnang kernel:
>>> [252300.060304]  ? try_to_del_timer_sync+0x4d/0x80 Feb  4 20:04:46
>>> tettnang kernel: [252300.060306]  ? del_timer_sync+0x35/0x40 Feb  4
>>> 20:04:46 tettnang kernel: [252300.060309]  ? schedule_timeout+0x17a/0x3b0
>>> Feb  4 20:04:46 tettnang kernel: [252300.060312]  ?
>>> preempt_count_add+0x79/0xb0 Feb  4 20:04:46 tettnang kernel:
>>> [252300.060315]  ? _raw_spin_lock_irqsave+0x25/0x50 Feb  4 20:04:46
>>> tettnang kernel: [252300.060321]  ? md_rdev_init+0xb0/0xb0 [md_mod] Feb
>>> 4 20:04:46 tettnang kernel: [252300.060327]  ? md_thread+0xf9/0x160
>>> [md_mod] Feb  4 20:04:46 tettnang kernel: [252300.060330]  ?
>>> r1bio_pool_alloc+0x20/0x20 [raid1] Feb  4 20:04:46 tettnang kernel:
>>> [252300.060336]  md_thread+0xf9/0x160 [md_mod] Feb  4 20:04:46 tettnang
>>> kernel: [252300.060340]  ? finish_wait+0x80/0x80 Feb  4 20:04:46 tettnang
>>> kernel: [252300.060344]  kthread+0x112/0x130 Feb  4 20:04:46 tettnang
>>> kernel: [252300.060346]  ? kthread_create_worker_on_cpu+0x70/0x70 Feb  4
>>> 20:04:46 tettnang kernel: [252300.060350]  ret_from_fork+0x35/0x40
>>>
>>> I saw that there was a similar problem with raid10 and an upstream patch
>>>
>>> e820d55cb99dd93ac2dc949cf486bb187e5cd70d
>>> md: fix raid10 hang issue caused by barrier
>>> by  Guoqing Jiang
>>>
>>> I wonder if there is a similar fix needed for raid1?
>> Seems not, the calltrace tells the previous write superblock IO was not
>> finish as expected,
>> there is a report for raid5 which has similar problem with md_super_wait
>> in the link [1]. Maybe
>> you can disable blk-mq to narrow down the issue as well.
> I already did for 4 weeks. I didn't saw this with blk-mq disabled (for scsi
> and md), though this may be by luck.

Then I guess it maybe related to blk-mq, which scheduler are you used 
with blk-mq?
And maybe you can switch it to see if it is caused by specified 
scheduler or not.

>> [1] |https://bbs.archlinux.org/viewtopic.php?id=243520
> I found this bug report in debian:
>
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904822

Thanks, the bug report also said it didn't happen after disable blk-mq.

Regards,
Guoqing