syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=96e4/1/0x4000000000000000 softirq=234264/234264 fqs=7
rcu: 	(detected by 1, t=10502 jiffies, g=225297, q=837 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 4428 Comm: syz.5.12093 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:lock_acquire kernel/locking/lockdep.c:5868 [inline]
RIP: 0010:lock_acquire+0x176/0x370 kernel/locking/lockdep.c:5825
Code: 00 00 00 65 48 8b 05 81 be 7d 12 8b 90 9c 0b 00 00 85 d2 0f 85 98 00 00 00 9c 8f 04 24 fa 48 c7 c7 71 87 29 8e e8 ba 19 d3 09 <45> 89 e8 44 89 e1 89 da 65 ff 05 0b 05 7e 12 4c 8b 14 24 44 89 f6
RSP: 0018:ffffc90000007e10 EFLAGS: 00000096
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff8e298771 RDI: ffffffff8c400b80
RBP: ffff8880b8428418 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f1b816956c0(0000) GS:ffff888123dee000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f703bbd1286 CR3: 000000002c032000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock_irq+0x36/0x50 kernel/locking/spinlock.c:174
 __run_hrtimer kernel/time/hrtimer.c:2036 [inline]
 __hrtimer_run_queues+0x1b7/0x9c0 kernel/time/hrtimer.c:2096
 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2215
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
 __sysvec_apic_timer_interrupt+0x109/0x470 arch/x86/kernel/apic/apic.c:1068
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0x9e/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:unwind_next_frame+0x4ec/0x2090 arch/x86/kernel/unwind_orc.c:520
Code: 00 00 fc ff df 4c 8d 79 05 4c 89 fa 48 c1 ea 03 0f b6 04 02 4c 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 51 15 00 00 0f b6 41 05 <83> e0 07 0f 84 53 fe ff ff 3c 01 0f 84 7b fe ff ff 4c 8d 41 04 4c
RSP: 0018:ffffc90003f070c0 EFLAGS: 00000246
RAX: 0000000000000002 RBX: 0000000000000001 RCX: ffffffff91c2e858
RDX: 0000000000000005 RSI: 0000000000000000 RDI: ffffffff913a4af4
RBP: ffffc90003f071c8 R08: ffffffff91c2e882 R09: 0000000000000007
R10: 0000000000000200 R11: 000000000000aee9 R12: ffffc90003f071d0
R13: ffffc90003f07180 R14: ffffc90003f071b5 R15: ffffffff91c2e85d
 __unwind_start+0x3cd/0x7e0 arch/x86/kernel/unwind_orc.c:787
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0x73/0xf0 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 save_stack+0x162/0x1e0 mm/page_owner.c:165
 __reset_page_owner+0x84/0x190 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950
 __folio_put+0x3b4/0x5f0 mm/swap.c:112
 folio_put_refs include/linux/mm.h:2144 [inline]
 collapse_file+0x333f/0x3a50 mm/khugepaged.c:2643
 collapse_scan_file mm/khugepaged.c:2773 [inline]
 collapse_single_pmd+0x293f/0x45a0 mm/khugepaged.c:2808
 madvise_collapse+0x329/0x750 mm/khugepaged.c:3234
 madvise_vma_behavior+0x107c/0x2240 mm/madvise.c:1364
 madvise_walk_vmas+0x2fe/0xa90 mm/madvise.c:1713
 madvise_do_behavior+0x1ea/0x510 mm/madvise.c:1908
 do_madvise+0x238/0x290 mm/madvise.c:2006
 __do_sys_madvise mm/madvise.c:2015 [inline]
 __se_sys_madvise mm/madvise.c:2013 [inline]
 __x64_sys_madvise+0xa9/0x110 mm/madvise.c:2013
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1b8079de59
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:00007f1b81695028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f1b80a26090 RCX: 00007f1b8079de59
RDX: 0000000000000019 RSI: 0000000000600722 RDI: 0000200000000000
RBP: 00007f1b80833e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1b80a26128 R14: 00007f1b80a26090 R15: 00007ffd2c3feb58
 </TASK>
rcu: rcu_preempt kthread starved for 10487 jiffies! g225297 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:27592 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7326
 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2123
 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2325
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 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: 1 UID: 0 PID: 1220 Comm: kworker/1:2 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 fqdir_free_fn
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_single+0x204/0x710 kernel/smp.c:702
Code: bc 24 ce 00 00 00 48 89 84 24 d8 00 00 00 e8 a3 f9 ff ff 89 44 24 2c 0f 1f 44 00 00 e8 15 75 0c 00 eb 07 e8 0e 75 0c 00 f3 90 <8b> 9c 24 c8 00 00 00 31 ff 83 e3 01 89 de e8 69 6f 0c 00 85 db 75
RSP: 0018:ffffc90005aa7a40 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff81fd5b27
RDX: ffff888029cea540 RSI: ffffffff81fd5b12 RDI: ffff888029cea540
RBP: ffffc90005aa7b88 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000000 R14: ffff8880b843c540 R15: ffff8880b843c688
FS:  0000000000000000(0000) GS:ffff888123eee000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000560b6b1a4300 CR3: 000000007a8e0000 CR4: 00000000003526f0
DR0: 0000000000000084 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 rcu_barrier kernel/rcu/tree.c:3909 [inline]
 rcu_barrier+0x2a4/0x6d0 kernel/rcu/tree.c:3846
 fqdir_free_fn+0x32/0x140 net/ipv4/inet_fragment.c:164
 process_one_work+0xa23/0x1940 kernel/workqueue.c:3322
 process_scheduled_works kernel/workqueue.c:3405 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3486
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>