INFO: task kworker/u4:12:16615 blocked for more than 143 seconds.
      Not tainted 5.9.0-rc8-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:12   state:D stack:24800 pid:16615 ppid:     2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xec9/0x2280 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 rwsem_down_write_slowpath+0x603/0xc60 kernel/locking/rwsem.c:1235
 __down_write kernel/locking/rwsem.c:1389 [inline]
 down_write+0x137/0x150 kernel/locking/rwsem.c:1532
 unregister_shrinker+0x9b/0x2c0 mm/vmscan.c:404
 nfsd_reply_cache_shutdown+0x22/0x2c0 fs/nfsd/nfscache.c:203
 nfsd_exit_net+0x15f/0x490 fs/nfsd/nfsctl.c:1507
 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:187
 cleanup_net+0x4ea/0xa00 net/core/net_namespace.c:604
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task syz-executor.1:29095 blocked for more than 145 seconds.
      Not tainted 5.9.0-rc8-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.1  state:D stack:28952 pid:29095 ppid:  6885 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xec9/0x2280 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 rwsem_down_write_slowpath+0x603/0xc60 kernel/locking/rwsem.c:1235
 __down_write kernel/locking/rwsem.c:1389 [inline]
 down_write+0x137/0x150 kernel/locking/rwsem.c:1532
 register_shrinker_prepared+0x1e/0x180 mm/vmscan.c:375
 register_shrinker+0x31/0x40 mm/vmscan.c:390
 nfsd_reply_cache_init+0x1f0/0x480 fs/nfsd/nfscache.c:171
 nfsd_init_net+0x20b/0x640 fs/nfsd/nfsctl.c:1477
 ops_init+0xaf/0x470 net/core/net_namespace.c:152