rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4172/1:b..l
	(detected by 1, t=10502 jiffies, g=7833, q=52)
task:syz-executor    state:R  running task     stack:19960 pid: 4172 ppid:  4169 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6780
 irqentry_exit+0x53/0x80 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__sanitizer_cov_trace_switch+0x3f/0xe0 kernel/kcov.c:-1
Code: f8 07 0f 87 ac 00 00 00 b9 8b 00 00 00 0f a3 c1 0f 83 9e 00 00 00 4c 8b 16 4d 85 d2 0f 84 92 00 00 00 4c 8b 04 c5 80 d8 ae 8a <4c> 8b 4c 24 20 65 4c 8b 1d d4 28 82 7e 31 d2 eb 08 48 ff c2 49 39
RSP: 0018:ffffc90002eafa78 EFLAGS: 00000202
RAX: 0000000000000000 RBX: 0000000000000063 RCX: 000000000000008b
RDX: ffff888028ad1dc0 RSI: ffffffff8cc14c70 RDI: 0000000000000063
RBP: ffffc90002eafbe0 R08: 0000000000000001 R09: ffffffff81d966a1
R10: 0000000000000002 R11: ffff888028ad1dc0 R12: dffffc0000000000
R13: ffffc90002eafcc0 R14: ffff888079bf3325 R15: ffff888079bf3325
 link_path_walk+0x581/0xd90 fs/namei.c:2288
 path_lookupat+0xa9/0x450 fs/namei.c:2454
 filename_lookup+0x230/0x5c0 fs/namei.c:2484
 user_path_at_empty+0x40/0x180 fs/namei.c:2883
 user_path_at include/linux/namei.h:57 [inline]
 ksys_umount fs/namespace.c:1779 [inline]
 __do_sys_umount fs/namespace.c:1787 [inline]
 __se_sys_umount fs/namespace.c:1785 [inline]
 __x64_sys_umount+0xf0/0x170 fs/namespace.c:1785
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa3ca6e7c97
RSP: 002b:00007ffe640011d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa3ca6e7c97
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe64001290
RBP: 00007ffe64001290 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffe64002320
R13: 00007fa3ca76889d R14: 0000000000016383 R15: 00007ffe64002360
 </TASK>
rcu: rcu_preempt kthread starved for 10528 jiffies! g7833 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:27000 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1f0 kernel/sched/core.c:6459
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4423 Comm: syz.1.44 Not tainted 5.15.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1d2/0x240 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x137a/0x14d0 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3932 [inline]
 rcu_sched_clock_irq+0xa38/0x1150 kernel/rcu/tree.c:2619
 update_process_times+0x196/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x386/0x550 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1690 [inline]
 __hrtimer_run_queues+0x55b/0xcf0 kernel/time/hrtimer.c:1754
 hrtimer_interrupt+0x392/0x980 kernel/time/hrtimer.c:1816
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x13b/0x4b0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: 31 60 f6 ff 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ae ec 19 f7 48 89 df e8 06 41 1b f7 e8 b1 f0 3d f7 fb bf 01 00 00 00 <e8> d6 83 0e f7 65 8b 05 b7 a0 b9 75 85 c0 74 02 5b c3 e8 64 bc b7
RSP: 0018:ffffc9000337fbc0 EFLAGS: 00000282
RAX: 40a611b075989c00 RBX: ffff888024455c80 RCX: ffffffff96a92f03
RDX: dffffc0000000000 RSI: ffffffff8aab18e0 RDI: 0000000000000001
RBP: 0000000000000000 R08: ffffffff8186bfe0 R09: ffffed100488ab91
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000021
R13: dffffc0000000000 R14: ffff888024456118 R15: ffff888024455c80
 spin_unlock_irq include/linux/spinlock.h:413 [inline]
 get_signal+0x13ee/0x14e0 kernel/signal.c:2903
 arch_do_signal_or_restart+0xbd/0x12b0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x97/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
 do_syscall_64+0x47/0x80 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff724f63967
Code: ff ff 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
RSP: 002b:00007ff722d890e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007ff72518b168 RCX: 00007ff724f63969
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007ff72518b168
RBP: 00007ff72518b160 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ff72518b16c
R13: 0000000000000000 R14: 00007fffe3ee6170 R15: 00007fffe3ee6258
 </TASK>