INFO: task kworker/u4:6:21284 blocked for more than 143 seconds.
      Not tainted 5.11.0-rc4-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:6    state:D stack:24464 pid:21284 ppid:     2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
 context_switch kernel/sched/core.c:4313 [inline]
 __schedule+0x90c/0x21a0 kernel/sched/core.c:5064
 schedule+0xcf/0x270 kernel/sched/core.c:5143
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:5202
 __mutex_lock_common kernel/locking/mutex.c:1033 [inline]
 __mutex_lock+0x81a/0x1110 kernel/locking/mutex.c:1103
 ip_set_net_exit+0x194/0x5b0 net/netfilter/ipset/ip_set_core.c:2393
 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:187
 cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:604
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Showing all locks held in the system:
1 lock held by khungtaskd/1629:
 #0: ffffffff8b3738a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6254
1 lock held by systemd-journal/4892:
1 lock held by in:imklog/8167:
 #0: ffff8880150ed270 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:947
4 locks held by kworker/u4:6/21284:
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline]
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline]
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline]
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline]
 #0: ffff88814079f138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x871/0x15f0 kernel/workqueue.c:2246
 #1: ffffc90005f9fda8 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x8a5/0x15f0 kernel/workqueue.c:2250
 #2: ffffffff8ca46d50 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x9b/0xb10 net/core/net_namespace.c:566
 #3: ffffffff8fc15fb8 (nfnl_subsys_ipset){+.+.}-{3:3}, at: ip_set_net_exit+0x194/0x5b0 net/netfilter/ipset/ip_set_core.c:2393
2 locks held by syz-executor.3/23587:

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

NMI backtrace for cpu 0
CPU: 0 PID: 1629 Comm: khungtaskd Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x230 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+0xd43/0xfa0 kernel/hung_task.c:294
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 98 Comm: kworker/u4:2 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:lockdep_enabled kernel/locking/lockdep.c:87 [inline]
RIP: 0010:lockdep_softirqs_on+0x4c/0x340 kernel/locking/lockdep.c:4216
Code: 83 c0 03 0f b6 14 11 65 48 8b 1c 25 00 f0 01 00 38 d0 7c 08 84 d2 0f 85 2a 02 00 00 8b 3d c8 f0 aa 0b 85 ff 0f 84 e7 01 00 00 <65> 8b 05 1d 0b a9 7e 85 c0 0f 85 d8 01 00 00 65 48 8b 2c 25 00 f0
RSP: 0018:ffffc9000117fbe8 EFLAGS: 00000002
RAX: 0000000000000007 RBX: ffff888011311bc0 RCX: 1ffffffff1a07cdb
RDX: 0000000000000000 RSI: ffffffff81448213 RDI: 0000000000000001
RBP: ffffffff889c4385 R08: 0000000000000000 R09: ffff88802c419d03
R10: ffffffff8178996d R11: 0000000000000000 R12: ffffffff889c4385
R13: ffff8880140a0bc0 R14: dffffc0000000000 R15: ffffffff889c45c0
FS:  0000000000000000(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00c0b3430 CR3: 000000006dd7d000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __local_bh_enable_ip+0xcd/0x110 kernel/softirq.c:184
 spin_unlock_bh include/linux/spinlock.h:399 [inline]
 batadv_nc_purge_paths+0x2a5/0x3a0 net/batman-adv/network-coding.c:467
 batadv_nc_worker+0x868/0xe50 net/batman-adv/network-coding.c:718
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296