On 2024/7/17 11:53, Yu Kuai wrote:
Hi,
在 2024/07/16 17:30, YangYang 写道:
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.
Yes, you're right. Please explain this in commit message as well.
Got it.
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@xxxxxxxx>
---
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);
Take a look at del_gendisk(), between freeze and unfreeze queue, I
notice that there is also device_del() here, which means it will wait
for all sysfs readers/writers to be done, so related sysfs api can't
issue IO to trigger blk_queue_enter(). And this behaviour does't look
reasonable, we never forbit this.
Then take a look at scsi sysfs api, I notice that scsi_rescan_device()
can be called and issue IO. Hence other than the 'open_mutex', same
deadlock still exist:
t1: t2
store_state_field
scsi_rescan_device
scsi_attach_vpd
scsi_get_vpd_buf
scsi_vpd_inquiry
scsi_execute_cmd
del_gendisk
bdev_unhash
blk_freeze_queue_start
blk_queue_enter
device_del
kobject_del
sysfs_remove_dir
I didn't test this, just by code review, and I could be wrong. And
I don't check all the procedures between freeze and unfreeze yet.
These sysfs nodes are in different directories, the scsi node located
at /sys/bus/scsi/devices/0:0:0:0 and the gendisk node located at
/sys/block/sda. Would it be necessary to wait for the completion of
the scsi sysfs nodes' read/write operations before removing the
gendisk sysfs node?
Thanks.
