rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (0 ticks this GP) idle=c264/1/0x4000000000000000 softirq=84747/84747 fqs=1 rcu: (detected by 1, t=10502 jiffies, g=67693, q=92 ncpus=2) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 55 Comm: kworker/0:1H Not tainted 6.16.0-rc3-syzkaller-00233-g35e261cd95dd #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: events_highpri snd_vmidi_output_work RIP: 0010:debug_smp_processor_id+0x0/0x20 lib/smp_processor_id.c:59 Code: e8 f5 0a 1a f6 e8 c0 4c f4 ff 90 65 ff 0d 78 fb 4b 08 e9 40 ff ff ff 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1e fa 48 c7 c6 60 7e 15 8c 48 c7 c7 a0 7e 15 8c e9 f9 fe ff RSP: 0018:ffffc90000007cd0 EFLAGS: 00000083 RAX: 0000000000000000 RBX: ffffffff9afc9ac8 RCX: 0000000000000002 RDX: ffffffff9afc9ab0 RSI: ffffffff84e2257c RDI: ffffffff9afc9ac8 RBP: 0000000000000002 R08: 0000000000000001 R09: fffff52000000f98 R10: 0000000000000003 R11: 0000000000000001 R12: ffffffff84e2257c R13: dffffc0000000000 R14: ffff8880597fb340 R15: 1ffff92000000fac FS: 0000000000000000(0000) GS:ffff888124752000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000006000 CR3: 0000000051a67000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_is_watching_curr_cpu include/linux/context_tracking.h:128 [inline] rcu_is_watching+0x12/0xc0 kernel/rcu/tree.c:745 trace_lock_release include/trace/events/lock.h:69 [inline] lock_release+0x201/0x2f0 kernel/locking/lockdep.c:5882 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline] _raw_spin_unlock_irqrestore+0x1a/0x80 kernel/locking/spinlock.c:194 debug_object_deactivate+0x1ec/0x3a0 lib/debugobjects.c:888 debug_hrtimer_deactivate kernel/time/hrtimer.c:450 [inline] debug_deactivate kernel/time/hrtimer.c:490 [inline] __run_hrtimer kernel/time/hrtimer.c:1729 [inline] __hrtimer_run_queues+0x46f/0xad0 kernel/time/hrtimer.c:1825 hrtimer_interrupt+0x397/0x8e0 kernel/time/hrtimer.c:1887 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline] __sysvec_apic_timer_interrupt+0x108/0x3f0 arch/x86/kernel/apic/apic.c:1056 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline] sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1050 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194 Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 36 00 15 f6 48 89 df e8 1e 54 15 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 01 00 00 00 e8 55 74 05 f6 65 8b 05 4e 6a 49 08 85 c0 74 16 5b RSP: 0018:ffffc9000130f7c0 EFLAGS: 00000246 RAX: 0000000000000006 RBX: ffffffff90228460 RCX: 0000000000000007 RDX: 0000000000000000 RSI: ffffffff8de1a526 RDI: ffffffff8c157ee0 RBP: 0000000000000293 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff90a81657 R11: 0000000000000001 R12: 0000000000000005 R13: dffffc0000000000 R14: 0000000000000000 R15: ffff888030fa0800 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline] find_slot+0x15c/0x1d0 sound/core/seq/oss/seq_oss_midi.c:119 snd_seq_oss_midi_input+0x10a/0xa20 sound/core/seq/oss/seq_oss_midi.c:528 snd_seq_oss_event_input+0x182/0x250 sound/core/seq/oss/seq_oss_event.c:427 __snd_seq_deliver_single_event sound/core/seq/seq_clientmgr.c:651 [inline] __snd_seq_deliver_single_event+0x124/0x1c0 sound/core/seq/seq_clientmgr.c:638 snd_seq_deliver_single_event+0x58c/0x720 sound/core/seq/seq_clientmgr.c:714 __deliver_to_subscribers sound/core/seq/seq_clientmgr.c:769 [inline] deliver_to_subscribers sound/core/seq/seq_clientmgr.c:798 [inline] snd_seq_deliver_event+0x2c8/0x850 sound/core/seq/seq_clientmgr.c:848 snd_seq_kernel_client_dispatch+0x14f/0x180 sound/core/seq/seq_clientmgr.c:2554 snd_vmidi_output_work+0x1d1/0x390 sound/core/seq/seq_virmidi.c:157 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3321 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402 kthread+0x3c2/0x780 kernel/kthread.c:464 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: rcu_preempt kthread starved for 10500 jiffies! g67693 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:27784 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000 Call Trace: context_switch kernel/sched/core.c:5396 [inline] __schedule+0x116a/0x5de0 kernel/sched/core.c:6785 __schedule_loop kernel/sched/core.c:6863 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:6878 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x1ea/0xb00 kernel/rcu/tree.c:2054 rcu_gp_kthread+0x270/0x380 kernel/rcu/tree.c:2256 kthread+0x3c2/0x780 kernel/kthread.c:464 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 rcu: Stack dump where RCU GP kthread last ran: CPU: 1 UID: 0 PID: 65 Comm: kworker/u8:4 Not tainted 6.16.0-rc3-syzkaller-00233-g35e261cd95dd #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: events_unbound toggle_allocation_gate RIP: 0010:handle_softirqs+0x1dd/0x8e0 kernel/softirq.c:565 Code: 88 6c 24 26 4c 89 7c 24 18 48 c7 c7 20 a1 ab 8b e8 a8 09 04 0a 65 66 c7 05 d6 04 50 12 00 00 e8 b9 15 47 00 fb bb ff ff ff ff <49> c7 c7 c0 c0 20 8e 41 0f bc dc 83 c3 01 0f 85 a4 00 00 00 e9 b1 RSP: 0000:ffffc90000a08f28 EFLAGS: 00000212 RAX: 00000000016cae20 RBX: 00000000ffffffff RCX: 0000000000000002 RDX: 0000000000000000 RSI: ffffffff8de1a526 RDI: ffffffff8c157ee0 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff90a81657 R11: 0000000000000001 R12: 0000000000000100 R13: 000000000000000a R14: 1ffff920001411ed R15: ffffed10041d6488 FS: 0000000000000000(0000) GS:ffff888124852000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c298fd0 CR3: 000000000e382000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __do_softirq kernel/softirq.c:613 [inline] invoke_softirq kernel/softirq.c:453 [inline] __irq_exit_rcu+0x109/0x170 kernel/softirq.c:680 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline] sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1050 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:csd_lock_wait kernel/smp.c:340 [inline] RIP: 0010:smp_call_function_many_cond+0xd7b/0x1510 kernel/smp.c:885 Code: e8 2a 1a 0c 00 45 85 ed 74 46 48 8b 14 24 49 89 d6 49 89 d5 49 c1 ee 03 41 83 e5 07 4d 01 e6 41 83 c5 03 e8 c7 1e 0c 00 f3 90 <41> 0f b6 06 41 38 c5 7c 08 84 c0 0f 85 6f 05 00 00 8b 43 08 31 ff RSP: 0000:ffffc9000210f8a0 EFLAGS: 00000293 RAX: 0000000000000000 RBX: ffff8880b84421e0 RCX: ffffffff81b001cd RDX: ffff888020eb2440 RSI: ffffffff81b001a9 RDI: 0000000000000005 RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000 R13: 0000000000000003 R14: ffffed101708843d R15: ffff8880b853b580 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1052 on_each_cpu include/linux/smp.h:71 [inline] smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2691 [inline] smp_text_poke_batch_finish+0x27b/0xdb0 arch/x86/kernel/alternative.c:2901 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146 jump_label_update+0x376/0x550 kernel/jump_label.c:919 static_key_enable_cpuslocked+0x1b7/0x270 kernel/jump_label.c:210 static_key_enable+0x1a/0x20 kernel/jump_label.c:223 toggle_allocation_gate mm/kfence/core.c:850 [inline] toggle_allocation_gate+0xfa/0x280 mm/kfence/core.c:842 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3321 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402 kthread+0x3c2/0x780 kernel/kthread.c:464 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245