rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-...!: (1 GPs behind) idle=b76c/1/0x4000000000000000 softirq=105343/105344 fqs=31 (t=10500 jiffies g=170525 q=44 ncpus=2) rcu: rcu_preempt kthread timer wakeup didn't happen for 10364 jiffies! g170525 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 rcu: Possible timer handling issue on cpu=1 timer-softirq=80724 rcu: rcu_preempt kthread starved for 10365 jiffies! g170525 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 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:I stack:27888 pid:16 ppid:2 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5245 [inline] __schedule+0x107f/0x4030 kernel/sched/core.c:6562 schedule+0xb9/0x180 kernel/sched/core.c:6638 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168 rcu_gp_fqs_loop+0x303/0x1350 kernel/rcu/tree.c:1706 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 rcu: Stack dump where RCU GP kthread last ran: Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline] NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline] NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741 CPU: 0 PID: 21250 Comm: syz.0.5174 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 RIP: 0010:cake_heapify+0x4e4/0x560 net/sched/sch_cake.c:1510 Code: 38 c1 0f 8c a6 fd ff ff 4c 89 f7 e8 66 c7 74 f9 e9 99 fd ff ff e8 ac 9f 23 f9 eb 05 e8 a5 9f 23 f9 48 83 c4 20 5b 41 5c 41 5d <41> 5e 41 5f 5d c3 e8 91 9f 23 f9 48 c7 c7 20 f9 d9 8d 4c 89 e6 48 RSP: 0018:ffffc9000cd56fe0 EFLAGS: 00000282 RAX: ffffffff885e8164 RBX: 000000000000078b RCX: 0000000000080000 RDX: ffffc9000e08c000 RSI: 000000000007ffff RDI: 0000000000080000 RBP: 000000000000078b R08: ffffffff90af23ef R09: 1ffffffff215e47d R10: dffffc0000000000 R11: fffffbfff215e47e R12: ffff88805f29c2d8 R13: ffff88805f298000 R14: 000000000000078b R15: 0000000000000f18 FS: 00007fdbc065f6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fdbbf84f270 CR3: 000000002ea56000 CR4: 00000000003526f0 Call Trace: cake_drop net/sched/sch_cake.c:1575 [inline] cake_enqueue+0x44c1/0x86a0 net/sched/sch_cake.c:1949 qdisc_enqueue include/net/sch_generic.h:854 [inline] netem_dequeue+0xcbb/0x1390 net/sched/sch_netem.c:736 dequeue_skb net/sched/sch_generic.c:295 [inline] qdisc_restart net/sched/sch_generic.c:400 [inline] __qdisc_run+0x25a/0x1660 net/sched/sch_generic.c:418 __dev_xmit_skb net/core/dev.c:3995 [inline] __dev_queue_xmit+0x1121/0x3810 net/core/dev.c:4337 packet_snd net/packet/af_packet.c:3133 [inline] packet_sendmsg+0x3b95/0x4de0 net/packet/af_packet.c:3164 sock_sendmsg_nosec net/socket.c:718 [inline] __sock_sendmsg net/socket.c:730 [inline] __sys_sendto+0x497/0x650 net/socket.c:2153 __do_sys_sendto net/socket.c:2165 [inline] __se_sys_sendto net/socket.c:2161 [inline] __x64_sys_sendto+0xda/0xf0 net/socket.c:2161 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fdbbf79ce59 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:00007fdbc065f028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007fdbbfa15fa0 RCX: 00007fdbbf79ce59 RDX: 000000000000000e RSI: 0000200000000240 RDI: 0000000000000009 RBP: 00007fdbbf832e6f R08: 00002000000001c0 R09: 0000000000000014 R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fdbbfa16038 R14: 00007fdbbfa15fa0 R15: 00007fff844e8498 vkms_vblank_simulate: vblank timer overrun