rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (3 ticks this GP) idle=660c/1/0x4000000000000000 softirq=21018/21018 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=12869, q=908 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6899 Comm: syz.0.225 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:lock_is_held_type+0x123/0x190
Code: e8 92 16 00 00 b8 ff ff ff ff 65 0f c1 05 35 64 26 07 83 f8 01 75 44 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <75> 4c 41 f7 c4 00 02 00 00 74 01 fb 65 48 8b 05 f9 23 26 07 48 3b
RSP: 0018:ffffc90000007c28 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 4cc66d07101d5100
RDX: ffff8880284eb980 RSI: ffffffff8dba8f4b RDI: ffffffff8be33880
RBP: 00000000ffffffff R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000f7c R12: 0000000000000046
R13: ffff8880284eb980 R14: ffff88803b881300 R15: 0000000000000003
FS:  00007febd84956c0(0000) GS:ffff8880b8614000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f72b517c440 CR3: 0000000023196000 CR4: 00000000000006f0
Call Trace:
 <IRQ>
 advance_sched+0x160/0xc90
 __hrtimer_run_queues+0x52c/0xc60
 hrtimer_interrupt+0x45b/0xaa0
 __sysvec_apic_timer_interrupt+0x10b/0x410
 sysvec_apic_timer_interrupt+0xa1/0xc0
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20
RIP: 0010:preempt_count_sub+0x30/0x170
Code: 48 bb 00 00 00 00 00 fc ff df 48 c7 c0 20 13 ac 99 48 c1 e8 03 0f b6 04 18 84 c0 0f 85 d1 00 00 00 83 3d 52 15 1c 18 00 75 25 <65> 8b 05 59 c2 10 11 89 c1 81 e1 ff ff ff 7f 39 cf 7f 2a 81 ff ff
RSP: 0018:ffffc900086a7300 EFLAGS: 00000246
RAX: 0000000000000004 RBX: dffffc0000000000 RCX: ffffffff99ac1303
RDX: 0000000000000003 RSI: ffffffff8dba8f4b RDI: 0000000000000001
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff822e691a
R10: dffffc0000000000 R11: fffff940008b7b41 R12: dffffc0000000000
R13: 0000000000000008 R14: 0000000000000001 R15: ffff88805fffa840
 pfn_valid+0x3bc/0x490
 page_table_check_clear+0x21/0x700
 unmap_page_range+0x3445/0x4370
 unmap_vmas+0x399/0x580
 exit_mmap+0x248/0xb50
 __mmput+0x118/0x420
 exit_mm+0x1da/0x2c0
 do_exit+0x648/0x2300
 do_group_exit+0x21c/0x2d0
 get_signal+0x1286/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 exit_to_user_mode_loop+0x75/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7febd758eba9
Code: Unable to access opcode bytes at 0x7febd758eb7f.
RSP: 002b:00007febd8495038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: 00000000000000b0 RBX: 00007febd77d5fa0 RCX: 00007febd758eba9
RDX: 0000000000000000 RSI: 00002000000007c0 RDI: 0000000000000008
RBP: 00007febd7611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007febd77d6038 R14: 00007febd77d5fa0 R15: 00007ffffa131738
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12869 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=5106
rcu: rcu_preempt kthread starved for 10502 jiffies! g12869 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27160 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_timeout+0x12b/0x270
 rcu_gp_fqs_loop+0x301/0x1540
 rcu_gp_kthread+0x99/0x390
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30
 </TASK>
