rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (2 GPs behind) idle=ce8c/1/0x4000000000000000 softirq=23168/23183 fqs=0 rcu: (detected by 0, t=10506 jiffies, g=18157, q=544 ncpus=2) Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 5193 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 RIP: 0010:__raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline] RIP: 0010:_raw_spin_unlock+0x23/0x50 kernel/locking/spinlock.c:186 Code: 90 90 90 90 90 90 90 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ca bc 54 f6 48 89 df e8 22 54 55 f6 bf 01 00 00 00 38 4b 47 f6 65 8b 05 c1 79 25 07 85 c0 74 07 5b e9 92 9a c7 f5 RSP: 0018:ffffc90000a08c60 EFLAGS: 00000046 RAX: 0000000000000001 RBX: ffff8880570982e8 RCX: 0000000000000001 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000001 RBP: ffff888058914950 R08: ffff8880570982eb R09: 1ffff1100ae1305d R10: dffffc0000000000 R11: ffffed100ae1305e R12: ffff888057098340 R13: ffff888057098000 R14: 1872fced0ab0cc00 R15: ffff888058915800 FS: 00007f42a65fb880(0000) GS:ffff88812623e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fd55587de9c CR3: 000000007bda0000 CR4: 0000000000350ef0 Call Trace: spin_unlock include/linux/spinlock.h:391 [inline] advance_sched+0x99f/0xc90 net/sched/sch_taprio.c:986 __run_hrtimer kernel/time/hrtimer.c:1777 [inline] __hrtimer_run_queues+0x52c/0xc60 kernel/time/hrtimer.c:1841 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1041 [inline] __sysvec_apic_timer_interrupt+0x10b/0x410 arch/x86/kernel/apic/apic.c:1058 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1052 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:__might_resched+0xe2/0x610 kernel/sched/core.c:8889 Code: 0d 00 75 1f c6 05 cf 28 d5 0d 01 48 c7 c7 c0 4b 6a 8b be b9 22 00 00 48 c7 c2 c0 54 6a 8b e8 35 e6 0b 00 e8 d0 81 b4 09 85 c0 <74> 46 48 c7 c7 a0 d3 f3 8d be ff ff ff ff e8 cb 7d b4 09 85 c0 74 RSP: 0018:ffffc9000483fca0 EFLAGS: 00000202 RAX: 0000000000000001 RBX: 1ffff92000907f9c RCX: ffff88807be28000 RDX: 0000000000000000 RSI: ffffffff8d8f29f0 RDI: ffffffff8bbf05e0 RBP: ffffc9000483fdb8 R08: ffffc9000483fc6f R09: ffffc9000483fc60 R10: dffffc0000000000 R11: fffff52000907f8e R12: ffffc9000483fe40 R13: dffffc0000000000 R14: ffff88807835fbe8 R15: ffff888025458000 dput+0x26/0x2b0 fs/dcache.c:903 path_put+0x39/0x60 fs/namei.c:626 do_readlinkat+0x28b/0x500 fs/stat.c:595 __do_sys_readlink fs/stat.c:613 [inline] __se_sys_readlink fs/stat.c:610 [inline] __x64_sys_readlink+0x7f/0x90 fs/stat.c:610 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f42a5f153a7 Code: 00 00 90 48 83 ec 10 48 63 ff 45 31 c9 45 31 c0 6a 00 31 c9 e8 8a 20 f9 ff 48 83 c4 18 c3 0f 1f 44 00 00 b8 59 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 21 ba 0d 00 f7 d8 64 89 02 48 RSP: 002b:00007ffc1547ace8 EFLAGS: 00000246 ORIG_RAX: 0000000000000059 RAX: ffffffffffffffda RBX: 00007ffc1547b1c0 RCX: 00007f42a5f153a7 RDX: 0000000000000400 RSI: 00007ffc1547acf0 RDI: 00007ffc1547b1c0 RBP: 00007ffc1547acf0 R08: 00000000000001e0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000400 R13: 000055668d0c1100 R14: 00005566a2c384a0 R15: 00007ffc1547bbe0 rcu: rcu_preempt kthread starved for 10506 jiffies! g18157 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:27288 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5325 [inline] __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929 __schedule_loop kernel/sched/core.c:7011 [inline] schedule+0x165/0x360 kernel/sched/core.c:7026 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: CPU: 0 UID: 0 PID: 4571 Comm: kworker/u8:8 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 Workqueue: events_unbound toggle_allocation_gate RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline] RIP: 0010:smp_call_function_many_cond+0xd38/0x12d0 kernel/smp.c:877 Code: 89 ee 83 e6 01 31 ff e8 b6 73 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 61 6f 0b 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 45 6f 0b 00 eb e4 44 RSP: 0018:ffffc9000dec7640 EFLAGS: 00000293 RAX: 0000000000000000 RBX: 1ffff11017127ffd RCX: ffff88803200dac0 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc9000dec77c0 R08: ffffffff8f7cd477 R09: 1ffffffff1ef9a8e R10: dffffc0000000000 R11: fffffbfff1ef9a8f R12: ffff8880b893ffe8 R13: dffffc0000000000 R14: ffff8880b883b240 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88812613e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000600 CR3: 000000000dd38000 CR4: 0000000000350ef0 Call Trace: on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1043 on_each_cpu include/linux/smp.h:71 [inline] smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2713 [inline] smp_text_poke_batch_finish+0x5f9/0x1130 arch/x86/kernel/alternative.c:2923 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146 static_key_enable_cpuslocked+0x128/0x250 kernel/jump_label.c:210 static_key_enable+0x1a/0x20 kernel/jump_label.c:223 toggle_allocation_gate+0xad/0x240 mm/kfence/core.c:852 process_one_work kernel/workqueue.c:3263 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245