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

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Message-ID: <1859a975-8c53-140c-f5b5-898ad5e7f653@huaweicloud.com>
Date: Tue, 16 Jul 2024 17:15:05 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Yang Yang <yang.yang@...o.com>, Jens Axboe <axboe@...nel.dk>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block: fix deadlock between sd_remove & sd_release

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().

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);
>