INFO: task pool_workqueue_:3 blocked for more than 147 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:pool_workqueue_ state:D stack:28792 pid:3     tgid:3     ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7058
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7115
 __mutex_lock_common kernel/locking/mutex.c:676 [inline]
 __mutex_lock+0x81b/0x1060 kernel/locking/mutex.c:760
 exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343
 synchronize_rcu_expedited+0x28e/0x460 kernel/rcu/tree_exp.h:957
 wq_unregister_lockdep kernel/workqueue.c:4816 [inline]
 pwq_release_workfn+0x5e6/0xa70 kernel/workqueue.c:5112
 kthread_worker_fn+0x30d/0xc50 kernel/kthread.c:1010
 kthread+0x3c2/0x780 kernel/kthread.c:463