Hello,
While testing the v4.4-rc1 dm-mpath driver with queue_without_daemon set
to no in /etc/multipath.conf and after having stopped multipathd I
noticed the following:
* Multiple kpartx processes were unkillable.
* Several blkid tasks got stuck (see also the blkid call trace below).
* Multiple kworker threads were consuming 100% CPU.
I hadn't seen this behavior with previous kernel versions.
The blkid call trace is as follows:
INFO: task blkid:13768 blocked for more than 120 seconds.
Tainted: G E 4.4.0-rc1+ #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D ffff8803f76b3818 0 13768 1 0x00000006
ffff8803f76b3818 ffff88045af31f40 ffff880438509f40 0000000000000046
0000000000000046 000000003b9a0000 ffffffff81602720 0000000000000000
ffffffffffffc000 ffffffff81d34f68 ffffffff810df4c1 ffffffff00000000
Call Trace:
[<ffffffff81515d42>] schedule+0x42/0x90
[<ffffffff81519e7f>] schedule_timeout+0x17f/0x1d0
[<ffffffff81515290>] io_schedule_timeout+0x70/0xb0
[<ffffffff81516451>] bit_wait_io+0x31/0x50
[<ffffffff81516029>] __wait_on_bit_lock+0x69/0xa0
[<ffffffff81110145>] __lock_page+0xa5/0xb0
[<ffffffff81121fb8>] truncate_inode_pages_range+0x3d8/0x6b0
[<ffffffff81122310>] truncate_inode_pages+0x10/0x20
[<ffffffff811af6c4>] kill_bdev+0x34/0x40
[<ffffffff811af741>] __blkdev_put+0x71/0x1b0
[<ffffffff811af8da>] blkdev_put+0x5a/0x170
[<ffffffff811afa0f>] blkdev_close+0x1f/0x30
[<ffffffff81178ef3>] __fput+0xc3/0x200
[<ffffffff811790b9>] ____fput+0x9/0x10
[<ffffffff81076363>] task_work_run+0x63/0xb0
[<ffffffff81059a7a>] do_exit+0x13a/0x3f0
[<ffffffff81059d89>] do_group_exit+0x59/0xd0
[<ffffffff81067eec>] get_signal+0x1ec/0x400
[<ffffffff810058b0>] do_signal+0x20/0x110
[<ffffffff810024ed>] syscall_return_slowpath+0x12d/0x190
[<ffffffff8151b5b1>] int_ret_from_sys_call+0x25/0x9f
1 lock held by blkid/13768:
#0: (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811af70a>]
__blkdev_put+0x3a/0x1b0
The perf tool reported the following call stack for the kworker threads:
multipath_clone_and_map
map_request
dm_mq_queue_rq
__blk_mq_run_hw_queue
blk_mq_run_work_fn
process_one_work
worker_thread
kthread
ret_from_fork
Bart.
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