syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4396/2:b..l
	(detected by 0, t=10502 jiffies, g=10089, q=91)
task:udevd           state:R  running task     stack:25504 pid: 4396 ppid:  3548 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:seqcount_lockdep_reader_access+0x17a/0x1c0 include/linux/seqlock.h:106
Code: ff 4d 85 ed 75 16 e8 a5 60 a2 ff eb 15 e8 9e 60 a2 ff e8 39 0b cc 07 4d 85 ed 74 ea e8 8f 60 a2 ff fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 27 00 00 00 00 66 43 c7 44 27 09 00 00 43 c6 44 27 0b 00
RSP: 0018:ffffc9000344f840 EFLAGS: 00000293
RAX: ffffffff81d56191 RBX: 0000000000000000 RCX: ffff888020425940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000344f900 R08: dffffc0000000000 R09: fffffbfff1ad157e
R10: fffffbfff1ad157e R11: 1ffffffff1ad157d R12: dffffc0000000000
R13: 0000000000000200 R14: ffffffff81d53d2c R15: 1ffff92000689f08
 read_seqbegin include/linux/seqlock.h:897 [inline]
 read_seqbegin_or_lock include/linux/seqlock.h:1191 [inline]
 prepend_path+0x2bc/0xbb0 fs/d_path.c:172
 d_absolute_path+0x9e/0x140 fs/d_path.c:235
 tomoyo_get_absolute_path security/tomoyo/realpath.c:101 [inline]
 tomoyo_realpath_from_path+0x331/0x610 security/tomoyo/realpath.c:276
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x1cd/0x510 security/tomoyo/file.c:822
 security_inode_getattr+0xcf/0x120 security/security.c:1348
 vfs_getattr+0x26/0x3a0 fs/stat.c:157
 vfs_fstat fs/stat.c:182 [inline]
 __do_sys_newfstat fs/stat.c:421 [inline]
 __se_sys_newfstat fs/stat.c:418 [inline]
 __x64_sys_newfstat+0x104/0x1d0 fs/stat.c:418
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f45aad07ad7
RSP: 002b:00007ffc45d39908 EFLAGS: 00000246 ORIG_RAX: 0000000000000005
RAX: ffffffffffffffda RBX: 0000565541993000 RCX: 00007f45aad07ad7
RDX: 0000000000000000 RSI: 00007ffc45d39950 RDI: 0000000000000009
RBP: 0000000000000001 R08: 00000000000000d0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000565506a0595f
R13: 0000565506a16660 R14: 0000000000000000 R15: 0000000000000009
 </TASK>
rcu: rcu_preempt kthread starved for 10530 jiffies! g10089 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:27584 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:722