INFO: task kworker/u4:6:10676 blocked for more than 143 seconds.
      Not tainted 5.8.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:6    D24272 10676      2 0x00004000
Workqueue: netns cleanup_net
Call Trace:
 context_switch kernel/sched/core.c:3430 [inline]
 __schedule+0x8e1/0x1eb0 kernel/sched/core.c:4155
 schedule+0xd0/0x2a0 kernel/sched/core.c:4230
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:4289
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x3e2/0x10d0 kernel/locking/mutex.c:1103
 ip_set_net_exit+0x192/0x650 net/netfilter/ipset/ip_set_core.c:2404
 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:186
 cleanup_net+0x4ea/0xa00 net/core/net_namespace.c:603
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Showing all locks held in the system:
1 lock held by khungtaskd/1148:
 #0: ffffffff89bbe640 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5779
1 lock held by in:imklog/6467:
 #0: ffff8880a48a73b0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:826
4 locks held by kworker/u4:6/10676:
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff8880a97ad138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240
 #1: ffffc90001b07da8 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244
 #2: ffffffff8a7a3f30 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xa00 net/core/net_namespace.c:565
 #3: ffffffff8d4aaa18 (&table[i].mutex){+.+.}-{3:3}, at: ip_set_net_exit+0x192/0x650 net/netfilter/ipset/ip_set_core.c:2404
2 locks held by syz-executor.1/604:

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1148 Comm: khungtaskd Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
 watchdog+0xd7d/0x1000 kernel/hung_task.c:295
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 523 Comm: kworker/u4:5 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:hlock_class kernel/locking/lockdep.c:174 [inline]
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4079 [inline]
RIP: 0010:__lock_acquire+0x719/0x56e0 kernel/locking/lockdep.c:4330
Code: 42 0f b6 04 30 84 c0 74 08 3c 03 0f 8e 18 31 00 00 41 3b 9c 24 c8 08 00 00 0f 8d 99 00 00 00 48 63 c3 48 8d 04 80 49 8d 2c c7 <48> 8d 7d 20 48 89 fa 48 c1 ea 03 42 0f b6 14 32 84 d2 74 09 80 fa
RSP: 0018:ffffc90002957a38 EFLAGS: 00000097
RAX: 0000000000000005 RBX: 0000000000000001 RCX: ffffffff8159411b
RDX: ffffffff8c5d3d58 RSI: 0000000000000008 RDI: ffffffff8c5d3e08
RBP: ffff8880a8388eb8 R08: 0000000000000000 R09: ffffffff8c58dae7
R10: fffffbfff18b1b5c R11: 0000000000000001 R12: ffff8880a83885c0
R13: 0000000000000004 R14: dffffc0000000000 R15: ffff8880a8388e90
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000073f4d4 CR3: 00000001cb6cf000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 lock_acquire+0x1f1/0xad0 kernel/locking/lockdep.c:4959
 rcu_lock_acquire include/linux/rcupdate.h:241 [inline]
 rcu_read_lock include/linux/rcupdate.h:634 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:407 [inline]
 batadv_nc_worker+0x12d/0xe50 net/batman-adv/network-coding.c:718
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293