rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (1 GPs behind) idle=576c/1/0x4000000000000000 softirq=24075/24075 fqs=7 rcu: (detected by 1, t=10502 jiffies, g=20625, q=1259 ncpus=2) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 6386 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 RIP: 0010:rcu_preempt_read_enter kernel/rcu/tree_plugin.h:391 [inline] RIP: 0010:__rcu_read_lock+0x2d/0x60 kernel/rcu/tree_plugin.h:414 Code: fa 53 65 48 8b 1d fb 16 95 11 48 81 c3 c4 04 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 18 03 8b 03 3d 00 00 00 40 7d 07 5b c3 cc cc cc cc cc 90 0f 0b 90 RSP: 0018:ffffc90000007cf8 EFLAGS: 00000046 RAX: 0000000000000000 RBX: ffff888030184244 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff888035551328 RBP: ffff88802eaea550 R08: ffff8880355512ab R09: 1ffff11006aaa255 R10: dffffc0000000000 R11: ffffed1006aaa256 R12: ffff888035551340 R13: ffff888035551000 R14: 18a8916a4c5fd2f7 R15: ffff88802eaeb000 FS: 0000000000000000(0000) GS:ffff888125214000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055b458a0aa38 CR3: 000000000e74a000 CR4: 00000000003526f0 Call Trace: rcu_read_lock include/linux/rcupdate.h:836 [inline] advance_sched+0x9f1/0xc90 net/sched/sch_taprio.c:991 __run_hrtimer kernel/time/hrtimer.c:1930 [inline] __hrtimer_run_queues+0x3c0/0xa20 kernel/time/hrtimer.c:1994 hrtimer_interrupt+0x44b/0x950 kernel/time/hrtimer.c:2113 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline] __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1067 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:60 [inline] RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:409 [inline] RIP: 0010:deref_stack_reg arch/x86/kernel/unwind_orc.c:419 [inline] RIP: 0010:unwind_next_frame+0xe05/0x2550 arch/x86/kernel/unwind_orc.c:614 Code: 00 00 41 83 3e 00 0f 95 c0 49 39 df 0f 96 c1 20 c1 49 39 dc 0f 97 c0 20 c8 3c 01 75 18 48 8d 43 08 4c 39 f8 0f 97 c1 4c 39 e0 <0f> 96 c0 84 c1 0f 85 bf 00 00 00 49 8d 7e 28 48 89 f8 48 c1 e8 03 RSP: 0018:ffffc900035d7318 EFLAGS: 00000283 RAX: ffffc900035d7768 RBX: ffffc900035d7760 RCX: 1ffff920006bae01 RDX: ffffffff90d69a90 RSI: 0000000000000002 RDI: ffffffff8c289e80 RBP: 1ffff920006bae7e R08: 000000000000000a R09: ffffffff8e95cce0 R10: ffffc900035d7438 R11: ffffffff81b105c0 R12: ffffc900035d8000 R13: 1ffff920006bae7f R14: ffffc900035d73e8 R15: ffffc900035d0000 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122 kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4569 [inline] slab_alloc_node mm/slub.c:4898 [inline] kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4905 kmem_alloc_batch lib/debugobjects.c:371 [inline] fill_pool+0x156/0x580 lib/debugobjects.c:420 debug_objects_fill_pool lib/debugobjects.c:742 [inline] debug_object_activate+0x4a3/0x580 lib/debugobjects.c:831 debug_rcu_head_queue kernel/rcu/rcu.h:236 [inline] __call_rcu_common kernel/rcu/tree.c:3116 [inline] call_rcu+0x43/0x890 kernel/rcu/tree.c:3251 slab_free_hook mm/slub.c:2653 [inline] slab_free mm/slub.c:6246 [inline] kmem_cache_free+0x462/0x650 mm/slub.c:6373 tear_down_vmas+0x312/0x520 mm/mmap.c:1262 exit_mmap+0x4b6/0x9e0 mm/mmap.c:1320 __mmput+0x118/0x430 kernel/fork.c:1178 exit_mm+0x18e/0x250 kernel/exit.c:581 do_exit+0x6a2/0x22c0 kernel/exit.c:963 do_group_exit+0x21b/0x2d0 kernel/exit.c:1117 __do_sys_exit_group kernel/exit.c:1128 [inline] __se_sys_exit_group kernel/exit.c:1126 [inline] __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1126 x64_sys_call+0x221a/0x2240 arch/x86/include/generated/asm/syscalls_64.h:232 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f9113ef16c5 Code: Unable to access opcode bytes at 0x7f9113ef169b. RSP: 002b:00007ffe1ac0e888 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000055b458a6d210 RCX: 00007f9113ef16c5 RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000 RBP: 000055b458a01910 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe1ac0e8d0 R14: 0000000000000000 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10485 jiffies! g20625 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:27968 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000 Call Trace: context_switch kernel/sched/core.c:5387 [inline] __schedule+0x17b4/0x5680 kernel/sched/core.c:7188 __schedule_loop kernel/sched/core.c:7267 [inline] schedule+0x164/0x360 kernel/sched/core.c:7282 schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99 rcu_gp_fqs_loop+0x312/0x11d0 kernel/rcu/tree.c:2095 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 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: 1 UID: 0 PID: 6273 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline] RIP: 0010:smp_call_function_many_cond+0xfcf/0x13d0 kernel/smp.c:892 Code: 79 45 8b 2e 44 89 ee 83 e6 01 31 ff e8 fa fc 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 a5 f8 0b 00 eb 37 f3 90 <43> 0f b6 04 2c 84 c0 75 10 41 f7 06 01 00 00 00 74 1e e8 8a f8 0b RSP: 0000:ffffc90003947840 EFLAGS: 00000293 RAX: ffffffff81b9d866 RBX: ffff8880b873c148 RCX: ffff888026c89ec0 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: ffffc90003947970 R08: ffffffff903380f7 R09: 1ffffffff206701e R10: dffffc0000000000 R11: fffffbfff206701f R12: 1ffff110170c8589 R13: dffffc0000000000 R14: ffff8880b8642c48 R15: 0000000000000000 FS: 00007f91145d9880(0000) GS:ffff888125314000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055b458a4a9b0 CR3: 000000007fb90000 CR4: 00000000003526f0 Call Trace: on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1057 __flush_tlb_multi arch/x86/include/asm/paravirt.h:46 [inline] flush_tlb_multi arch/x86/mm/tlb.c:1361 [inline] flush_tlb_mm_range+0x5c3/0x10b0 arch/x86/mm/tlb.c:1451 flush_tlb_page arch/x86/include/asm/tlbflush.h:345 [inline] ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:104 wp_page_copy mm/memory.c:3925 [inline] do_wp_page+0x3da7/0x4cc0 mm/memory.c:4320 handle_pte_fault mm/memory.c:6427 [inline] __handle_mm_fault mm/memory.c:6549 [inline] handle_mm_fault+0x151d/0x3170 mm/memory.c:6718 do_user_addr_fault+0xa73/0x1340 arch/x86/mm/fault.c:1334 handle_page_fault arch/x86/mm/fault.c:1474 [inline] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618 RIP: 0033:0x7f9113eb5b3b Code: 04 07 0f 85 a9 00 00 00 f3 0f 6f 47 10 48 8b 57 18 66 48 0f 7e c0 48 3b 78 18 75 7b 48 3b 7a 10 75 75 48 8b 77 10 48 89 50 18 <66> 0f d6 42 10 48 81 f9 ff 03 00 00 76 28 48 8b 57 20 48 85 d2 74 RSP: 002b:00007ffe1ac0e7c0 EFLAGS: 00010246 RAX: 00007f9113ff21d0 RBX: 000055b458a2c540 RCX: 0000000000002261 RDX: 000055b458a4a9a0 RSI: 00007f9113ff21d0 RDI: 000055b458a2c540 RBP: 00007f9113ff1ac0 R08: 0000000000002760 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00000000000049c0 R13: 000055b458a30f00 R14: 0000000000001de0 R15: 00007f9113ff1ac0