INFO: task rcu_tasks_kthre:12 blocked for more than 143 seconds. Not tainted syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:rcu_tasks_kthre state:D stack:27920 pid:12 ppid:2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5257 [inline] __schedule+0x1089/0x4140 kernel/sched/core.c:6584 schedule+0xb9/0x180 kernel/sched/core.c:6660 schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2144 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0x2c2/0x590 kernel/sched/completion.c:138 __synchronize_srcu+0x2b3/0x350 kernel/rcu/srcutree.c:1243 rcu_tasks_wait_gp+0x49d/0xb00 kernel/rcu/tasks.h:719 rcu_tasks_one_gp+0xb1c/0xce0 kernel/rcu/tasks.h:560 rcu_tasks_kthread+0x6e/0x90 kernel/rcu/tasks.h:588 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Showing all locks held in the system: 1 lock held by rcu_tasks_kthre/12: #0: ffffffff8db2e3f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xce0 kernel/rcu/tasks.h:543 1 lock held by rcu_tasks_trace/13: #0: ffffffff8db2ec30 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xce0 kernel/rcu/tasks.h:543 1 lock held by khungtaskd/28: #0: ffffffff8db2daa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #0: ffffffff8db2daa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #0: ffffffff8db2daa0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6669 2 locks held by getty/4026: #0: ffff88814ca52098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x430/0x1400 drivers/tty/n_tty.c:2198 3 locks held by kworker/u4:20/5695: #0: ffff888018479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 #1: ffffc90005097d00 ((work_completion)(&map->work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 #2: ffffffff8db337b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline] #2: ffffffff8db337b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3c0/0x890 kernel/rcu/tree_exp.h:962 3 locks held by kworker/u4:22/5698: 2 locks held by kworker/0:0/11166: #0: ffff888018472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 #1: ffffc900034f7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 3 locks held by kworker/u4:31/14004: #0: ffff888018479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 #1: ffffc900033c7d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267 #2: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263 2 locks held by syz.2.4635/21136: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline] #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3506 #1: ffffffff8db337b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:323 [inline] #1: ffffffff8db337b8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3c0/0x890 kernel/rcu/tree_exp.h:962 2 locks held by syz.4.4638/21141: #0: ffffffff8ed5ead0 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x324/0x5b0 net/core/net_namespace.c:504 #1: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: register_nexthop_notifier+0x84/0x240 net/ipv4/nexthop.c:3652 2 locks held by syz.1.4640/21150: #0: ffffffff8e5a54e8 (ppp_mutex){+.+.}-{3:3}, at: ppp_ioctl+0xdc/0x1b20 drivers/net/ppp/ppp_generic.c:727 #1: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: ppp_create_interface drivers/net/ppp/ppp_generic.c:3376 [inline] #1: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: ppp_unattached_ioctl drivers/net/ppp/ppp_generic.c:1065 [inline] #1: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: ppp_ioctl+0x8db/0x1b20 drivers/net/ppp/ppp_generic.c:731 1 lock held by syz.1.4640/21151: #0: ffffffff8e5a54e8 (ppp_mutex){+.+.}-{3:3}, at: ppp_ioctl+0xdc/0x1b20 drivers/net/ppp/ppp_generic.c:727 1 lock held by syz.5.4641/21155: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline] #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3506 1 lock held by syz.5.4641/21157: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline] #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3506 1 lock held by syz.5.4641/21158: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: __tun_chr_ioctl+0x3f3/0x1ed0 drivers/net/tun.c:3118 1 lock held by syz.5.4641/21159: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: __tun_chr_ioctl+0x3f3/0x1ed0 drivers/net/tun.c:3118 1 lock held by syz.5.4641/21161: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:698 [inline] #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3d/0x1b0 drivers/net/tun.c:3506 1 lock held by syz.5.4641/21162: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x54d/0xe80 net/core/dev_ioctl.c:571 1 lock held by syz.0.4643/21171: #0: ffffffff8db82da8 (event_mutex){+.+.}-{3:3}, at: perf_trace_destroy+0x2a/0x140 kernel/trace/trace_event_perf.c:239 1 lock held by syz.0.4643/21172: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: __tun_chr_ioctl+0x3f3/0x1ed0 drivers/net/tun.c:3118 1 lock held by syz.0.4643/21173: #0: ffffffff8ed6b9e8 (rtnl_mutex){+.+.}-{3:3}, at: __tun_chr_ioctl+0x3f3/0x1ed0 drivers/net/tun.c:3118 1 lock held by syz.0.4643/21174: 1 lock held by dhcpcd/21176: #0: ffff88805f088130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1813 [inline] #0: ffff88805f088130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3291 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 28 Comm: khungtaskd Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026 Call Trace: dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106 nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111 nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline] watchdog+0xf0e/0xf50 kernel/hung_task.c:377 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 5695 Comm: kworker/u4:20 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/15/2026 Workqueue: events_unbound nsim_dev_trap_report_work RIP: 0010:lockdep_softirqs_off+0x3bc/0x430 kernel/locking/lockdep.c:4565 Code: 48 89 d7 e8 f6 dd 6f 00 e9 fb fd ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 17 fe ff ff 48 89 df e8 49 de 6f 00 e9 0a fe ff ff <48> c7 c1 40 91 c6 97 80 e1 07 80 c1 03 38 c1 0f 8c 10 fe ff ff 48 RSP: 0018:ffffc900050979e0 EFLAGS: 00000002 RAX: 0000000000000004 RBX: ffff88802f8fe4a8 RCX: ffffffff97c69103 RDX: ffff88802f8fe478 RSI: 0000000000000201 RDI: ffffffff8613f560 RBP: ffffc90005097a90 R08: ffffc90005097a9f R09: ffffc90005097a60 R10: dffffc0000000000 R11: fffff52000a12f54 R12: ffff88802f8fe498 R13: dffffc0000000000 R14: 1ffff92000a12f40 R15: 000000000015cc06 FS: 0000000000000000(0000) GS:ffff8880b8d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6c8a9d49a0 CR3: 000000000d88e000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: __local_bh_disable_ip+0xb6/0x1a0 kernel/softirq.c:361 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:125 [inline] _raw_spin_lock_bh+0x18/0x50 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nsim_dev_trap_report drivers/net/netdevsim/dev.c:816 [inline] nsim_dev_trap_report_work+0x680/0xa80 drivers/net/netdevsim/dev.c:851 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295