rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P5898/1:b..l rcu: (detected by 1, t=10503 jiffies, g=14433, q=661 ncpus=2) task:syz-executor state:R running task stack:21736 pid:5898 ppid:5889 flags:0x00004002 Call Trace: context_switch kernel/sched/core.c:5381 [inline] __schedule+0x1553/0x45a0 kernel/sched/core.c:6700 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45 vprintk_emit+0x587/0x610 kernel/printk/printk.c:2342 dev_vprintk_emit+0x356/0x410 drivers/base/core.c:4953 dev_printk_emit+0xef/0x140 drivers/base/core.c:4964 __netdev_printk+0x3bf/0x4a0 net/core/dev.c:11520 netdev_info+0x11f/0x170 net/core/dev.c:11575 nsim_udp_tunnel_set_port+0x297/0x440 drivers/net/netdevsim/udp_tunnels.c:34 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:-1 [inline] udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:246 [inline] __udp_tunnel_nic_device_sync+0xa8c/0x13a0 net/ipv4/udp_tunnel_nic.c:289 udp_tunnel_nic_device_sync net/ipv4/udp_tunnel_nic.c:312 [inline] __udp_tunnel_nic_add_port+0xaf8/0xdb0 net/ipv4/udp_tunnel_nic.c:531 udp_tunnel_nic_add_port include/net/udp_tunnel.h:333 [inline] udp_tunnel_notify_add_rx_port+0x294/0x3e0 net/ipv4/udp_tunnel_core.c:127 geneve_socket_create drivers/net/geneve.c:614 [inline] geneve_sock_add+0x547/0x970 drivers/net/geneve.c:689 geneve_open+0xd2/0x140 drivers/net/geneve.c:731 __dev_open+0x2cb/0x430 net/core/dev.c:1519 __dev_change_flags+0x211/0x6a0 net/core/dev.c:8723 dev_change_flags+0x88/0x1a0 net/core/dev.c:8795 do_setlink+0xc58/0x4130 net/core/rtnetlink.c:2908 __rtnl_newlink net/core/rtnetlink.c:3706 [inline] rtnl_newlink+0x17da/0x20a0 net/core/rtnetlink.c:3753 rtnetlink_rcv_msg+0x869/0xfa0 net/core/rtnetlink.c:6475 netlink_rcv_skb+0x241/0x4d0 net/netlink/af_netlink.c:2545 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x751/0x8d0 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x4a9/0x6b0 net/socket.c:2200 __do_sys_sendto net/socket.c:2212 [inline] __se_sys_sendto net/socket.c:2208 [inline] __x64_sys_sendto+0xde/0xf0 net/socket.c:2208 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fcd4775d68e RSP: 002b:00007ffeacb05118 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 0000555586d45500 RCX: 00007fcd4775d68e RDX: 000000000000002c RSI: 00007fcd48544670 RDI: 0000000000000003 RBP: 0000000000000001 R08: 00007ffeacb05194 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 0000000000000000 R14: 00007fcd48544670 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10554 jiffies! g14433 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:27656 pid:17 ppid:2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5381 [inline] __schedule+0x1553/0x45a0 kernel/sched/core.c:6700 schedule+0xbd/0x170 kernel/sched/core.c:6774 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866 kthread+0x2fa/0x390 kernel/kthread.c:388 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 5972 Comm: syz.0.17 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 RIP: 0010:do_raw_spin_unlock+0x5/0x230 kernel/locking/spinlock_debug.c:138 Code: ff ff e8 6e e8 1c 09 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c 69 ff ff ff e8 29 d8 75 00 e9 5f ff ff ff 0f 1f 40 00 66 0f 1f 00 55 <41> 57 41 56 41 55 41 54 53 48 89 fb 49 bc 00 00 00 00 00 fc ff df RSP: 0018:ffffc90000007df0 EFLAGS: 00000046 RAX: 8df203cf09e44700 RBX: 0000000000000806 RCX: 8df203cf09e44700 RDX: 0000000000000000 RSI: ffffffff8acadb60 RDI: ffff8880b8e2b700 RBP: ffffc90000007e90 R08: ffffffff8e8b19af R09: 1ffffffff1d16335 R10: dffffc0000000000 R11: fffffbfff1d16336 R12: dffffc0000000000 R13: 00000035c4802880 R14: ffff8880b8e2b700 R15: 1ffff92000000fc0 FS: 0000555578ca5500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000020000006b000 CR3: 00000000221e3000 CR4: 00000000003506f0 Call Trace: __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:150 [inline] _raw_spin_unlock_irqrestore+0x79/0x120 kernel/locking/spinlock.c:194 hrtimer_interrupt+0x597/0x9c0 kernel/time/hrtimer.c:1886 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline] __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline] sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687 RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline] RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202 Code: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ea 97 d8 f6 48 89 df e8 a2 6c d9 f6 e8 1d 7f fd f6 fb bf 01 00 00 00 82 73 cc f6 65 8b 05 c3 a0 73 75 85 c0 74 02 5b c3 e8 40 88 70 RSP: 0018:ffffc90003497c78 EFLAGS: 00000286 RAX: 8df203cf09e44700 RBX: ffff88802e0de5c0 RCX: 8df203cf09e44700 RDX: dffffc0000000000 RSI: ffffffff8acac9e0 RDI: 0000000000000001 RBP: ffff88802e0dea58 R08: ffffffff8e8b19af R09: 1ffffffff1d16335 R10: dffffc0000000000 R11: fffffbfff1d16336 R12: 1ffff11005c1bd4b R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000 spin_unlock_irq include/linux/spinlock.h:401 [inline] get_signal+0x11f5/0x13f0 kernel/signal.c:2905 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302 do_syscall_64+0x61/0xa0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fdb6359ce59 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc2c74f3e8 EFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007fdb6359ce59 RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007fdb63815fac RBP: 0000000000001e5b R08: 0000000000745d1e R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fdb63815fac R14: 00007fdb63815fa8 R15: 00007fdb63815fa0 sched: RT throttling activated