syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4252/1:b..l P4029/1:b..l
	(detected by 0, t=10502 jiffies, g=4777, q=111)
task:udevd           state:R  running task     stack:    0 pid: 4029 ppid:  3654 flags:0x0000000c
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_notrace+0xc4/0x168 kernel/sched/core.c:6631
 rcu_is_watching+0xf4/0x134 kernel/rcu/tree.c:1124
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 percpu_ref_put_many include/linux/percpu-refcount.h:317 [inline]
 percpu_ref_put+0x30/0x234 include/linux/percpu-refcount.h:338
 css_put include/linux/cgroup.h:405 [inline]
 uncharge_page+0x39c/0x500 mm/memcontrol.c:6968
 __mem_cgroup_uncharge_list+0x7c/0xd4 mm/memcontrol.c:7004
 mem_cgroup_uncharge_list include/linux/memcontrol.h:720 [inline]
 release_pages+0x13c0/0x16e0 mm/swap.c:962
 __pagevec_release+0x84/0xf8 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x48c/0x1234 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x1c0/0x838 mm/shmem.c:1145
 evict+0x3c8/0x810 fs/inode.c:647
 iput_final fs/inode.c:1769 [inline]
 iput+0x6c4/0x77c fs/inode.c:1795
 dentry_unlink_inode+0x360/0x438 fs/dcache.c:380
 __dentry_kill+0x320/0x598 fs/dcache.c:586
 dentry_kill+0xc8/0x248 fs/dcache.c:-1
 dput+0x23c/0x458 fs/dcache.c:893
 __fput+0x494/0x7f8 fs/file_table.c:319
 ____fput+0x20/0x30 fs/file_table.c:339
 task_work_run+0x12c/0x1e0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 do_notify_resume+0x24b4/0x3128 arch/arm64/kernel/signal.c:949
 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+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
task:udevadm         state:R  running task     stack:    0 pid: 4252 ppid:  4179 flags:0x00000004
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 preempt_schedule_irq+0x90/0x214 kernel/sched/core.c:6780
 arm64_preempt_schedule_irq+0x14c/0x21c 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]
 seqcount_lockdep_reader_access include/linux/seqlock.h:105 [inline]
 read_seqbegin+0x21c/0x304 include/linux/seqlock.h:897
 d_alloc_parallel+0x2c4/0x1104 fs/dcache.c:2592
 __lookup_slow+0x104/0x380 fs/namei.c:1648
 lookup_slow+0x5c/0x80 fs/namei.c:1680
 walk_component+0x2b0/0x3a8 fs/namei.c:1976
 lookup_last fs/namei.c:2431 [inline]
 path_lookupat+0x13c/0x3d0 fs/namei.c:2455
 filename_lookup+0x180/0x414 fs/namei.c:2484
 user_path_at_empty+0x5c/0x1a0 fs/namei.c:2883
 do_readlinkat+0xd4/0x3e0 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+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/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 10483 jiffies! g4777 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+0x2f4/0x558 arch/arm64/kernel/process.c:521
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0xe00/0x1c0c kernel/sched/core.c:6376
 schedule+0x11c/0x1c8 kernel/sched/core.c:6459
 schedule_timeout+0x180/0x2c8 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x25c/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xc4/0x2a8 kernel/rcu/tree.c:2145
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 1:
task:syz.4.20        state:R  running task     stack:    0 pid: 4251 ppid:  4045 flags:0x00000000
Call trace:
 __switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
 0xffff80001f4c7540