rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 1-...!: (1 GPs behind) idle=88cc/1/0x4000000000000000 softirq=32874/32875 fqs=0 rcu: (detected by 0, t=10502 jiffies, g=21909, q=126 ncpus=2) Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 8402 Comm: syz.0.631 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 RIP: 0010:__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] RIP: 0010:_raw_spin_lock_irqsave+0x1e/0x60 kernel/locking/spinlock.c:162 Code: 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 53 48 89 fb 9c 5d fa f7 c5 00 02 00 00 75 39 bf 01 00 00 00 e8 42 ce 26 f6 74 24 10 48 8d 7b 18 45 31 c9 31 c9 41 b8 01 00 00 00 31 d2 31 RSP: 0018:ffffc90000a08d08 EFLAGS: 00000093 RAX: 0000000000010003 RBX: ffffffff9ad90c00 RCX: 1ffffffff3561818 RDX: 0000000000000000 RSI: ffffffff8b903140 RDI: 0000000000000001 RBP: 0000000000000002 R08: 0000000000000001 R09: ffffc90000a08d40 R10: 0000000000000000 R11: ffffffff9ad90c00 R12: dffffc0000000000 R13: ffff88807d656340 R14: ffffffff9ad90bf8 R15: 1ffff920001411a8 FS: 00007f972e3e26c0(0000) GS:ffff888124b0b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00002000003e9030 CR3: 000000007e750000 CR4: 00000000003526f0 Call Trace: debug_object_activate+0x14c/0x4c0 lib/debugobjects.c:818 debug_hrtimer_activate kernel/time/hrtimer.c:438 [inline] debug_activate kernel/time/hrtimer.c:477 [inline] enqueue_hrtimer+0x23/0x3b0 kernel/time/hrtimer.c:1081 __run_hrtimer kernel/time/hrtimer.c:1794 [inline] __hrtimer_run_queues+0x8ff/0xad0 kernel/time/hrtimer.c:1841 hrtimer_interrupt+0x397/0x8e0 kernel/time/hrtimer.c:1903 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1041 [inline] __sysvec_apic_timer_interrupt+0x10b/0x3f0 arch/x86/kernel/apic/apic.c:1058 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline] sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1052 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 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 16 f9 35 f6 48 89 df e8 fe 4c 36 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 01 00 00 00 e8 45 56 26 f6 65 8b 05 7e 65 3e 08 85 c0 74 16 5b RSP: 0018:ffffc9001b9cf760 EFLAGS: 00000246 RAX: 0000000000000006 RBX: ffff88807d465e80 RCX: 0000000000000006 RDX: 0000000000000000 RSI: ffffffff8da2a184 RDI: ffffffff8bf06cc0 RBP: 0000000000000246 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff9081f4d7 R11: 0000000000000001 R12: ffff888032e3f000 R13: 0000000000000246 R14: ffff88807d465e68 R15: ffffc9001b9cf8e8 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline] __skb_try_recv_datagram+0x172/0x4f0 net/core/datagram.c:267 __unix_dgram_recvmsg+0x1bc/0xc30 net/unix/af_unix.c:2601 unix_dgram_recvmsg+0xd0/0x110 net/unix/af_unix.c:2700 sock_recvmsg_nosec net/socket.c:1078 [inline] ____sys_recvmsg+0x5f9/0x6b0 net/socket.c:2848 ___sys_recvmsg+0x114/0x1a0 net/socket.c:2892 do_recvmmsg+0x2fe/0x750 net/socket.c:2987 __sys_recvmmsg net/socket.c:3061 [inline] __do_sys_recvmmsg net/socket.c:3084 [inline] __se_sys_recvmmsg net/socket.c:3077 [inline] __x64_sys_recvmmsg+0x22a/0x280 net/socket.c:3077 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f972d58efc9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f972e3e2038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007f972d7e6090 RCX: 00007f972d58efc9 RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003 RBP: 00007f972d611f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f972d7e6128 R14: 00007f972d7e6090 R15: 00007ffee5b05ca8 rcu: rcu_preempt kthread starved for 10502 jiffies! g21909 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:27224 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5325 [inline] __schedule+0x1190/0x5de0 kernel/sched/core.c:6929 __schedule_loop kernel/sched/core.c:7011 [inline] schedule+0xe7/0x3a0 kernel/sched/core.c:7026 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x675/0x7d0 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: 6503 Comm: kworker/u8:20 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+0xdfd/0x1600 kernel/smp.c:877 Code: 57 48 8b 54 24 10 4c 89 74 24 10 49 89 d5 48 89 d5 48 89 54 24 18 49 c1 ed 03 83 e5 07 4d 01 e5 83 c5 03 e8 e5 0c 0c 00 f3 90 <41> 0f b6 45 00 40 38 c5 7c 08 84 c0 0f 85 e0 05 00 00 8b 43 08 31 RSP: 0018:ffffc9001002f878 EFLAGS: 00000293 RAX: 0000000000000000 RBX: ffff8880b8540320 RCX: ffffffff81b0fd91 RDX: ffff888032af0000 RSI: ffffffff81b0fd6b RDI: 0000000000000005 RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000 R13: ffffed10170a8065 R14: 0000000000000001 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff888124a0b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2ffe1ff8 CR3: 000000000e182000 CR4: 00000000003526f0 Call Trace: on_each_cpu_cond_mask+0x40/0x90 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+0x27b/0xdb0 arch/x86/kernel/alternative.c:2923 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:852 [inline] toggle_allocation_gate+0xfa/0x280 mm/kfence/core.c:844 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263 process_scheduled_works kernel/workqueue.c:3346 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245