rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 GPs behind) idle=5b54/1/0x4000000000000002 softirq=10053/10055 fqs=174
(detected by 1, t=10505 jiffies, g=10417, q=114 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4510 Comm: syz.0.28 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:preempt_count arch/x86/include/asm/preempt.h:27 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0xc/0x60 kernel/kcov.c:216
Code: 89 fb e8 17 00 00 00 48 8b 3d f0 59 9d 0c 48 89 de 5b e9 27 22 50 00 00 00 cc cc 00 00 cc 48 8b 04 24 65 48 8b 0d 84 fb 7f 7e <65> 8b 15 85 fb 7f 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75
RSP: 0018:ffffc90000006ff8 EFLAGS: 00000046
RAX: ffffffff81a4ff24 RBX: ffffc900000071a0 RCX: ffff88807e335940
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900000070f0 R08: ffffc90000007177 R09: ffffc90000007140
R10: dffffc0000000000 R11: fffff52000000e2f R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90000007300
FS: 00007f085da4d6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fc63fff CR3: 0000000028e79000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
perf_prepare_sample+0xde4/0x2020 kernel/events/core.c:7630
__perf_event_output kernel/events/core.c:7730 [inline]
perf_event_output_forward+0x197/0x2f0 kernel/events/core.c:7750
__perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
perf_tp_event+0x38c/0xc00 kernel/events/core.c:10029
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10002
perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 92 31 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007740 EFLAGS: 00000206
RAX: 8a41d94fde4b3000 RBX: 1ffff92000000ef0 RCX: 8a41d94fde4b3000
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90000007828 R08: ffffffff90af42cf R09: 1ffffffff215e859
R10: dffffc0000000000 R11: fffffbfff215e85a R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3b900 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
__ip_queue_xmit+0x1174/0x1c10 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x1c92/0x31a0 net/ipv4/tcp_output.c:1405
tcp_delack_timer_handler+0x2a9/0x440 net/ipv4/tcp_timer.c:322
tcp_delack_timer+0x188/0x2e0 net/ipv4/tcp_timer.c:345
call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
expire_timers kernel/time/timer.c:1752 [inline]
__run_timers+0x53e/0x800 kernel/time/timer.c:2023
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 d0 fd dc 08 e8 eb 2c 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc900036278f8 EFLAGS: 00000282
RAX: 8a41d94fde4b3000 RBX: 0000000000000000 RCX: 8a41d94fde4b3000
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90003627950 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: ffff88807e335940
R13: dffffc0000000000 R14: ffff88802eba8000 R15: ffff8880b8e3b5d0
context_switch kernel/sched/core.c:5248 [inline]
__schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6731
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6755
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
__raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
_raw_spin_unlock+0x36/0x40 kernel/locking/spinlock.c:186
spin_unlock include/linux/spinlock.h:391 [inline]
futex_wake+0x419/0x4f0 kernel/futex/waitwake.c:183
do_futex+0x2e2/0x320 kernel/futex/syscalls.c:139
__do_sys_futex kernel/futex/syscalls.c:211 [inline]
__se_sys_futex+0x381/0x410 kernel/futex/syscalls.c:192
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: 0033:0x7f085cb9aeb9
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:00007f085da4d0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f085ce15fa8 RCX: 00007f085cb9aeb9
RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f085ce15fac
RBP: 00007f085ce15fa0 R08: 0032f7506eedf44c R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f085ce16038 R14: 00007ffc5288ade0 R15: 00007ffc5288aec8
rcu: rcu_preempt kthread starved for 9635 jiffies! g10417 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R running task stack:28112 pid:16 ppid:2 flags:0x00004000
Call Trace:
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 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+0x303/0x1340 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:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x159/0x1b0 arch/x86/kernel/kvm.c:1064
Code: 89 df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 4b 0f b6 1f e8 77 39 50 00 44 38 e3 75 10 66 90 0f 00 2d 59 ce 50 09 fb f4 16 ff ff ff fb e9 10 ff ff ff e8 37 f2 f3 08 89 f9 80 e1 07 38
RSP: 0018:ffffc900001e0880 EFLAGS: 00000246
RAX: 8dc89091a68ece00 RBX: 0000000000000003 RCX: 8dc89091a68ece00
RDX: dffffc0000000000 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc900001e0930 R08: ffffffff90af42cf R09: 1ffffffff215e859
R10: dffffc0000000000 R11: fffffbfff215e85a R12: 0000000000000003
R13: ffff8880b8f3b954 R14: dffffc0000000000 R15: 1ffff9200003c110
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555585b894e8 CR3: 000000007722b000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pv_wait arch/x86/include/asm/paravirt.h:603 [inline]
pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
__pv_queued_spin_lock_slowpath+0x616/0x9c0 kernel/locking/qspinlock.c:511
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [inline]
queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x265/0x2f0 kernel/locking/spinlock_debug.c:115
spin_lock include/linux/spinlock.h:351 [inline]
tcp_keepalive_timer+0x2f/0xda0 net/ipv4/tcp_timer.c:715
call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
expire_timers kernel/time/timer.c:1752 [inline]
__run_timers+0x53e/0x800 kernel/time/timer.c:2023
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:742
Code: 48 89 df e8 97 d1 9c f7 e9 44 ff ff ff e8 3d 07 f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 66 90 0f 00 2d 77 1c 50 00 fb f4 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffc90000177de8 EFLAGS: 000002c6
RAX: 8dc89091a68ece00 RBX: ffffffff8a3692b7 RCX: 8dc89091a68ece00
RDX: 0000000000000001 RSI: ffffffff8a8c1220 RDI: ffffffff8adf0d20
RBP: ffffc90000177f20 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: 1ffff9200002efc8
R13: dffffc0000000000 R14: ffff888017739dc0 R15: 0000000000000001
default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
cpuidle_idle_call kernel/sched/idle.c:191 [inline]
do_idle+0x20d/0x5a0 kernel/sched/idle.c:303
cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401
start_secondary+0xe4/0xf0 arch/x86/kernel/smpboot.c:281
secondary_startup_64_no_verify+0xcf/0xdb