Comment 6 for bug 1428045

I believe we are running into the same bug on 4.4.0-34-generic. Here is the output of dmesg when the issue starts. Let me know if I can provide any more info.

INFO: task kworker/1:1:20481 blocked for more than 120 seconds.
      Not tainted 4.4.0-34-generic #53~14.04.1-Ubuntu
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/1:1 D ffff88007a0b7ce8 0 20481 2 0x00000080
Workqueue: cifsiod cifs_oplock_break [cifs]
 ffff88007a0b7ce8 ffff8800791b3700 ffff880075408000 ffff88007a0b8000
 0000000000000002 ffff88007a0b7d80 ffff88007ffcf960 ffffffff817f4210
 ffff88007a0b7d00 ffffffff817f3b25 0000000000000002 ffff88007a0b7d18
Call Trace:
 [<ffffffff817f4210>] ? out_of_line_wait_on_atomic_t+0xd0/0xd0
 [<ffffffff817f3b25>] schedule+0x35/0x80
 [<ffffffff817f4221>] bit_wait+0x11/0x50
 [<ffffffff817f3ec0>] __wait_on_bit+0x60/0x90
 [<ffffffff817f4210>] ? out_of_line_wait_on_atomic_t+0xd0/0xd0
 [<ffffffff817f3f62>] out_of_line_wait_on_bit+0x72/0x80
 [<ffffffff810bdca0>] ? autoremove_wake_function+0x40/0x40
 [<ffffffffc02bf5eb>] cifs_oplock_break+0x6b/0x3a0 [cifs]
 [<ffffffff81095970>] process_one_work+0x150/0x3f0
 [<ffffffff810960ea>] worker_thread+0x11a/0x470
 [<ffffffff817f34c9>] ? __schedule+0x359/0x980
 [<ffffffff81095fd0>] ? rescuer_thread+0x310/0x310
 [<ffffffff8109b849>] kthread+0xc9/0xe0
 [<ffffffff8109b780>] ? kthread_park+0x60/0x60
 [<ffffffff817f770f>] ret_from_fork+0x3f/0x70
 [<ffffffff8109b780>] ? kthread_park+0x60/0x60