linux-kernel - Re: [PATCH] block: fix deadlock between sd_remove & sd

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Message-ID: <451c8746-5260-4be6-b78d-54305c94ef73@vivo.com>
Date: Tue, 16 Jul 2024 17:30:42 +0800
From: YangYang <yang.yang@...o.com>
To: Yu Kuai <yukuai1@...weicloud.com>, "yukuai (C)" <yukuai3@...wei.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: fix deadlock between sd_remove & sd_release

On 2024/7/16 17:15, Yu Kuai wrote:
> Hi,
> 
> 在 2024/07/16 16:38, Yang Yang 写道:
>> Our test report the following hung task:
>>
>> [ 2538.459400] INFO: task "kworker/0:0":7 blocked for more than 188 seconds.
>> [ 2538.459427] Call trace:
>> [ 2538.459430]  __switch_to+0x174/0x338
>> [ 2538.459436]  __schedule+0x628/0x9c4
>> [ 2538.459442]  schedule+0x7c/0xe8
>> [ 2538.459447]  schedule_preempt_disabled+0x24/0x40
>> [ 2538.459453]  __mutex_lock+0x3ec/0xf04
>> [ 2538.459456]  __mutex_lock_slowpath+0x14/0x24
>> [ 2538.459459]  mutex_lock+0x30/0xd8
>> [ 2538.459462]  del_gendisk+0xdc/0x350
>> [ 2538.459466]  sd_remove+0x30/0x60
>> [ 2538.459470]  device_release_driver_internal+0x1c4/0x2c4
>> [ 2538.459474]  device_release_driver+0x18/0x28
>> [ 2538.459478]  bus_remove_device+0x15c/0x174
>> [ 2538.459483]  device_del+0x1d0/0x358
>> [ 2538.459488]  __scsi_remove_device+0xa8/0x198
>> [ 2538.459493]  scsi_forget_host+0x50/0x70
>> [ 2538.459497]  scsi_remove_host+0x80/0x180
>> [ 2538.459502]  usb_stor_disconnect+0x68/0xf4
>> [ 2538.459506]  usb_unbind_interface+0xd4/0x280
>> [ 2538.459510]  device_release_driver_internal+0x1c4/0x2c4
>> [ 2538.459514]  device_release_driver+0x18/0x28
>> [ 2538.459518]  bus_remove_device+0x15c/0x174
>> [ 2538.459523]  device_del+0x1d0/0x358
>> [ 2538.459528]  usb_disable_device+0x84/0x194
>> [ 2538.459532]  usb_disconnect+0xec/0x300
>> [ 2538.459537]  hub_event+0xb80/0x1870
>> [ 2538.459541]  process_scheduled_works+0x248/0x4dc
>> [ 2538.459545]  worker_thread+0x244/0x334
>> [ 2538.459549]  kthread+0x114/0x1bc
>>
>> [ 2538.461001] INFO: task "fsck.":15415 blocked for more than 188 seconds.
>> [ 2538.461014] Call trace:
>> [ 2538.461016]  __switch_to+0x174/0x338
>> [ 2538.461021]  __schedule+0x628/0x9c4
>> [ 2538.461025]  schedule+0x7c/0xe8
>> [ 2538.461030]  blk_queue_enter+0xc4/0x160
>> [ 2538.461034]  blk_mq_alloc_request+0x120/0x1d4
>> [ 2538.461037]  scsi_execute_cmd+0x7c/0x23c
>> [ 2538.461040]  ioctl_internal_command+0x5c/0x164
>> [ 2538.461046]  scsi_set_medium_removal+0x5c/0xb0
>> [ 2538.461051]  sd_release+0x50/0x94
>> [ 2538.461054]  blkdev_put+0x190/0x28c
>> [ 2538.461058]  blkdev_release+0x28/0x40
>> [ 2538.461063]  __fput+0xf8/0x2a8
>> [ 2538.461066]  __fput_sync+0x28/0x5c
>> [ 2538.461070]  __arm64_sys_close+0x84/0xe8
>> [ 2538.461073]  invoke_syscall+0x58/0x114
>> [ 2538.461078]  el0_svc_common+0xac/0xe0
>> [ 2538.461082]  do_el0_svc+0x1c/0x28
>> [ 2538.461087]  el0_svc+0x38/0x68
>> [ 2538.461090]  el0t_64_sync_handler+0x68/0xbc
>> [ 2538.461093]  el0t_64_sync+0x1a8/0x1ac
>>
>>    T1:                T2:
>>    sd_remove
>>    del_gendisk
>>    __blk_mark_disk_dead
>>    blk_freeze_queue_start
>>    ++q->mq_freeze_depth
>>                    bdev_release
>>                   mutex_lock(&disk->open_mutex)
>>                    sd_release
>>                   scsi_execute_cmd
>>                   blk_queue_enter
>>                   wait_event(!q->mq_freeze_depth)
> 
> This looks wrong, there is a condition blk_queue_dying() in
> blk_queue_enter().

  584 static void __blk_mark_disk_dead(struct gendisk *disk)
  585 {
  ......
  591
  592     if (test_bit(GD_OWNS_QUEUE, &disk->state))
  593         blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);

SCSI does not set GD_OWNS_QUEUE, so QUEUE_FLAG_DYING is not set in
this scenario.

Thanks.

> 
> Thanks,
> Kuai
> 
>>    mutex_lock(&disk->open_mutex)
>>
>> This is a classic ABBA deadlock. To fix the deadlock, make sure we don't
>> try to acquire disk->open_mutex after freezing the queue.
>>
>> Signed-off-by: Yang Yang <yang.yang@...o.com>
>> ---
>>   block/genhd.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 8f1f3c6b4d67..c5fca3e893a0 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -663,12 +663,12 @@ void del_gendisk(struct gendisk *disk)
>>        */
>>       if (!test_bit(GD_DEAD, &disk->state))
>>           blk_report_disk_dead(disk, false);
>> -    __blk_mark_disk_dead(disk);
>>       /*
>>        * Drop all partitions now that the disk is marked dead.
>>        */
>>       mutex_lock(&disk->open_mutex);
>> +    __blk_mark_disk_dead(disk);
>>       xa_for_each_start(&disk->part_tbl, idx, part, 1)
>>           drop_partition(part);
>>       mutex_unlock(&disk->open_mutex);
>>
>