syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...0: (1 GPs behind) idle=0c2/1/0x4000000000000000 softirq=95961/95963 fqs=3056 
	(detected by 0, t=10502 jiffies, g=183253, q=1347)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3906 Comm: systemd-udevd Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:mark_lock+0x0/0x1710 kernel/locking/lockdep.c:3971
Code: 66 2e 0f 1f 84 00 00 00 00 00 be 00 00 01 00 48 c7 c7 c0 e6 f7 8b e8 2f f8 3e 02 48 98 c3 66 90 66 2e 0f 1f 84 00 00 00 00 00 <41> 57 41 56 41 55 41 54 55 53 48 83 ec 20 83 fa 08 76 51 48 c7 c0
RSP: 0018:ffffc90000da8aa0 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000040 RCX: ffffffff815a096e
RDX: 0000000000000000 RSI: ffff8880a21bcd90 RDI: ffff8880a21bc480
RBP: ffff8880a21bcd90 R08: 0000000000000000 R09: ffffffff8c5f49ef
R10: fffffbfff18be93d R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880a21bcdb2 R14: ffff8880a21bc480 R15: ffff8880a21bcd68
FS:  00007f22457e08c0(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b33021000 CR3: 00000000a1e41000 CR4: 00000000001526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 mark_usage kernel/locking/lockdep.c:3902 [inline]
 __lock_acquire+0x136e/0x5570 kernel/locking/lockdep.c:4380
 lock_acquire+0x1f3/0xae0 kernel/locking/lockdep.c:5006
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x94/0xce kernel/locking/spinlock.c:159
 debug_object_deactivate lib/debugobjects.c:710 [inline]
 debug_object_deactivate+0x101/0x300 lib/debugobjects.c:698
 debug_hrtimer_deactivate kernel/time/hrtimer.c:425 [inline]
 debug_deactivate kernel/time/hrtimer.c:486 [inline]
 __run_hrtimer kernel/time/hrtimer.c:1492 [inline]
 __hrtimer_run_queues+0x3cb/0xfc0 kernel/time/hrtimer.c:1588
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1650
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0xb2/0xf0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
RIP: 0010:__call_rcu kernel/rcu/tree.c:2927 [inline]
RIP: 0010:call_rcu+0x3ac/0x7b0 kernel/rcu/tree.c:2968
Code: 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 b9 02 00 00 48 83 3d 48 b0 54 08 00 0f 84 1b 01 00 00 48 8b 3c 24 57 9d <0f> 1f 44 00 00 48 83 c4 20 5b 5d 41 5c 41 5d 41 5e 41 5f c3 80 3c
RSP: 0018:ffffc900015a79d8 EFLAGS: 00000286
RAX: 1ffffffff136c789 RBX: ffff88808b1739f8 RCX: 1ffffffff1564571
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: 0000000000000286
RBP: ffff8880ae736ca8 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880ae736c00
R13: ffff8880ae736c98 R14: ffff8880ae736c50 R15: 0000000000000017
 dentry_free+0xc3/0x160 fs/dcache.c:350
 __dentry_kill+0x4c6/0x640 fs/dcache.c:593
 dentry_kill fs/dcache.c:717 [inline]
 dput+0x635/0xbc0 fs/dcache.c:878
 handle_mounts fs/namei.c:1389 [inline]
 step_into+0xc43/0x1990 fs/namei.c:1690
 walk_component+0x171/0x6a0 fs/namei.c:1866
 lookup_last fs/namei.c:2309 [inline]
 path_lookupat+0x1ba/0x830 fs/namei.c:2333
 filename_lookup+0x19f/0x560 fs/namei.c:2366
 user_path_at include/linux/namei.h:59 [inline]
 do_faccessat+0x129/0x820 fs/open.c:423
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f22446539c7
Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe197a3838 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 0000558f59622d60 RCX: 00007f22446539c7
RDX: 00746e657665752f RSI: 0000000000000000 RDI: 00007ffe197a3840
RBP: 00007ffe197a38b0 R08: 000000000000c440 R09: 0000000000001010
R10: 00007f2244911b58 R11: 0000000000000246 R12: 0000558f5942f856
R13: 0000558f59622bc0 R14: 00007ffe197a3840 R15: 0000558f59622930
rcu: rcu_preempt kthread starved for 4284 jiffies! g183253 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:29088 pid:   10 ppid:     2 flags:0x00004000
Call Trace:
 context_switch kernel/sched/core.c:3778 [inline]
 __schedule+0xea9/0x2230 kernel/sched/core.c:4527
 schedule+0xd0/0x2a0 kernel/sched/core.c:4602
 schedule_timeout+0x148/0x250 kernel/time/timer.c:1879
 rcu_gp_fqs_loop kernel/rcu/tree.c:1888 [inline]
 rcu_gp_kthread+0xae5/0x1b50 kernel/rcu/tree.c:2058
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294