syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=d5ac/1/0x4000000000000000 softirq=50205/50216 fqs=4
rcu: 	(detected by 0, t=10502 jiffies, g=56469, q=458 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 11144 Comm: syz.0.1295 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
RIP: 0010:debug_object_activate+0x12/0x420 lib/debugobjects.c:860
Code: e9 13 fc ff ff 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 41 57 41 56 41 55 41 54 53 48 83 ec 48 <49> 89 f6 48 89 fb 65 48 8b 05 10 70 8e 0e 48 89 44 24 40 48 8d 7c
RSP: 0018:ffffc90000a08d20 EFLAGS: 00000082
RAX: ffffffff81b346d3 RBX: ffff8880b8728300 RCX: ffff888029d81f00
RDX: 0000000000010000 RSI: ffffffff8bef7f00 RDI: ffff88807922f300
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520001411ac R12: 0000000000000001
R13: dffffc0000000000 R14: ffff88807922f300 R15: 0000000000000000
FS:  00007fb53a5806c0(0000) GS:ffff888125059000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa22e8a3000 CR3: 00000000360c7000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 debug_hrtimer_activate kernel/time/hrtimer.c:485 [inline]
 debug_activate kernel/time/hrtimer.c:528 [inline]
 enqueue_hrtimer+0xa9/0x2c0 kernel/time/hrtimer.c:1109
 __run_hrtimer kernel/time/hrtimer.c:2048 [inline]
 __hrtimer_run_queues+0x4ce/0xa10 kernel/time/hrtimer.c:2096
 hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2215
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__sanitizer_cov_trace_pc+0x45/0x70 kernel/kcov.c:222
Code: ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 24 17 00 00 00 74 2c 8b 91 f8 16 00 00 83 fa 02 75 21 48 8b 91 00 17 00 00 48 8b 32 <48> 8d 7e 01 8b 89 fc 16 00 00 48 39 cf 73 08 48 89 3a 48 89 44 f2
RSP: 0018:ffffc90005dcf1e8 EFLAGS: 00000246
RAX: ffffffff823f9a76 RBX: 0000000000066855 RCX: ffff888029d81f00
RDX: ffffc9000ead5000 RSI: 000000000002c2e3 RDI: 0000000000066855
RBP: 0000000000000000 R08: ffffffff823fb396 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8eb59c60 R12: ffffffff823fb396
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000066855
 page_ext_lookup+0x16/0x180 mm/page_ext.c:512
 page_ext_iter_begin include/linux/page_ext.h:133 [inline]
 page_table_check_set+0x214/0x510 mm/page_table_check.c:113
 page_table_check_ptes_set include/linux/page_table_check.h:83 [inline]
 set_ptes include/linux/pgtable.h:447 [inline]
 __copy_present_ptes mm/memory.c:1118 [inline]
 copy_present_ptes mm/memory.c:1197 [inline]
 copy_pte_range mm/memory.c:1320 [inline]
 copy_pmd_range+0x477a/0x5880 mm/memory.c:1408
 copy_pud_range mm/memory.c:1445 [inline]
 copy_p4d_range mm/memory.c:1469 [inline]
 copy_page_range+0xc26/0x1250 mm/memory.c:1555
 dup_mmap+0xf21/0x1d90 mm/mmap.c:1840
 dup_mm kernel/fork.c:1543 [inline]
 copy_mm+0x11a/0x480 kernel/fork.c:1595
 copy_process+0x1e3e/0x4390 kernel/fork.c:2289
 kernel_clone+0x2d7/0x940 kernel/fork.c:2748
 __do_sys_clone3 kernel/fork.c:3050 [inline]
 __se_sys_clone3+0x33c/0x360 kernel/fork.c:3029
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb53979de59
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:00007fb53a57fef8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b3
RAX: ffffffffffffffda RBX: 0000000000000058 RCX: 00007fb53979de59
RDX: 00007fb53a57ff10 RSI: 0000000000000058 RDI: 00007fb53a57ff10
RBP: 00007fb539833e6f R08: 0000000000000000 R09: 0000000000000058
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb539a26128 R14: 00007fb539a26090 R15: 00007fffed2f8d78
 </TASK>
rcu: rcu_preempt kthread starved for 10494 jiffies! g56469 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:27496 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7326
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2123
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2325
 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
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 3377 Comm: kworker/u8:12 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/10/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0x10b0/0x14b0 kernel/smp.c:892
Code: c0 75 73 41 8b 1e 89 de 83 e6 01 31 ff e8 d8 1e 0c 00 83 e3 01 48 bb 00 00 00 00 00 fc ff df 75 07 e8 84 1a 0c 00 eb 37 f3 90 <41> 0f b6 04 1c 84 c0 75 10 41 f7 06 01 00 00 00 74 1e e8 69 1a 0c
RSP: 0018:ffffc9000da9f720 EFLAGS: 00000293
RAX: ffffffff81ba57d7 RBX: dffffc0000000000 RCX: ffff888032fdbe00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000da9f860 R08: ffffffff90576ff7 R09: 1ffffffff20aedfe
R10: dffffc0000000000 R11: fffffbfff20aedff R12: 1ffff110170e81d1
R13: ffff8880b863c448 R14: ffff8880b8740e88 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888124f59000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9177a67ff8 CR3: 000000000e946000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1057
 on_each_cpu include/linux/smp.h:72 [inline]
 smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2773 [inline]
 smp_text_poke_batch_finish+0x5fd/0x1110 arch/x86/kernel/alternative.c:2983
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x128/0x240 kernel/jump_label.c:210
 static_key_enable+0x1a/0x20 kernel/jump_label.c:223
 toggle_allocation_gate+0xab/0x290 mm/kfence/core.c:911
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 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
 </TASK>