syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P3640/1:b..l
	(detected by 1, t=10502 jiffies, g=4345, q=138)
task:udevd           state:R  running task     stack:    0 pid: 3640 ppid:     1 flags:0x00000004
Call trace:
 __switch_to+0x308/0x5e8 arch/arm64/kernel/process.c:518
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xf10/0x1e48 kernel/sched/core.c:6376
 preempt_schedule_irq+0x90/0x274 kernel/sched/core.c:6780
 arm64_preempt_schedule_irq+0x174/0x2c4 arch/arm64/kernel/entry-common.c:260
 el1_interrupt+0x40/0x58 arch/arm64/kernel/entry-common.c:463
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
 lock_acquire+0x280/0x77c kernel/locking/lockdep.c:5626
 rcu_lock_acquire+0x40/0x4c include/linux/rcupdate.h:312
 rcu_read_lock include/linux/rcupdate.h:739 [inline]
 __d_lookup+0x90/0x6a0 fs/dcache.c:2428
 lookup_fast+0xcc/0x62c fs/namei.c:1621
 walk_component+0xf4/0x4cc fs/namei.c:1972
 link_path_walk+0x5a0/0xc38
 path_lookupat+0x90/0x3d0 fs/namei.c:2454
 filename_lookup+0x1c4/0x4c8 fs/namei.c:2484
 user_path_at_empty+0x5c/0x1a4 fs/namei.c:2883
 do_readlinkat+0xe8/0x4f0 fs/stat.c:442
 __do_sys_readlinkat fs/stat.c:469 [inline]
 __se_sys_readlinkat fs/stat.c:466 [inline]
 __arm64_sys_readlinkat+0x9c/0xb8 fs/stat.c:466
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
rcu: rcu_preempt kthread starved for 10502 jiffies! g4345 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:    0 pid:   15 ppid:     2 flags:0x00000008
Call trace:
 __switch_to+0x308/0x5e8 arch/arm64/kernel/process.c:518
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xf10/0x1e48 kernel/sched/core.c:6376
 schedule+0x11c/0x1c8 kernel/sched/core.c:6459
 schedule_timeout+0x1d8/0x344 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x26c/0x13d4 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xc4/0x2c4 kernel/rcu/tree.c:2145
 kthread+0x37c/0x45c kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 1:
task:syz.4.4         state:R  running task     stack:    0 pid: 4124 ppid:  4031 flags:0x00000001
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 sched_show_task+0x43c/0x574 kernel/sched/core.c:8640
 dump_cpu_task+0x84/0xa8 kernel/sched/core.c:10914
 rcu_check_gp_kthread_starvation+0x1f0/0x254 kernel/rcu/tree_stall.h:488
 print_other_cpu_stall+0x202c/0x2290 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+0x1894/0x1b8c kernel/rcu/tree.c:2619
 update_process_times+0x1d4/0x270 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x340/0x4f8 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1686 [inline]
 __hrtimer_run_queues+0x458/0xca4 kernel/time/hrtimer.c:1750
 hrtimer_interrupt+0x2c0/0xb64 kernel/time/hrtimer.c:1812
 timer_handler drivers/clocksource/arm_arch_timer.c:659 [inline]
 arch_timer_handler_virt+0x74/0x88 drivers/clocksource/arm_arch_timer.c:670
 handle_percpu_devid_irq+0x29c/0x7fc kernel/irq/chip.c:933
 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
 handle_irq_desc kernel/irq/irqdesc.c:651 [inline]
 handle_domain_irq+0xec/0x178 kernel/irq/irqdesc.c:706
 gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:758
 call_on_irq_stack+0x24/0x4c arch/arm64/kernel/entry.S:899
 do_interrupt_handler+0x74/0x94 arch/arm64/kernel/entry-common.c:267
 el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454
 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
 debug_lockdep_rcu_enabled+0xc/0x40 kernel/rcu/update.c:280
 __might_sleep+0x98/0xf0 kernel/sched/core.c:9580
 __might_fault+0x80/0x128 mm/memory.c:5325
 preserve_fpsimd_context arch/arm64/kernel/signal.c:180 [inline]
 setup_sigframe arch/arm64/kernel/signal.c:640 [inline]
 setup_rt_frame arch/arm64/kernel/signal.c:789 [inline]
 handle_signal arch/arm64/kernel/signal.c:830 [inline]
 do_signal arch/arm64/kernel/signal.c:905 [inline]
 do_notify_resume+0x1640/0x32b8 arch/arm64/kernel/signal.c:943
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
 el0_svc+0xfc/0x1f0 arch/arm64/kernel/entry-common.c:609
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584