rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10506 jiffies, g=8785, q=524 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10506 (4294955366-4294944860), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread timer wakeup didn't happen for 10505 jiffies! g8785 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x200
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=4110
rcu: rcu_preempt kthread starved for 10506 jiffies! g8785 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x200 ->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 stack:26792 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+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6279 Comm: syz.1.89 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_acquire+0x13d/0x360
Code: 00 6a 00 55 ff 74 24 30 e8 e0 02 00 00 48 83 c4 28 48 c7 c7 91 99 ba 8d e8 20 12 dd 09 b8 ff ff ff ff 65 0f c1 05 c3 9f 03 11 <83> f8 01 0f 85 c9 00 00 00 48 c7 44 24 30 00 00 00 00 9c 8f 44 24
RSP: 0018:ffffc900000077e0 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 10f41531f5da4200
RDX: 0000000000000000 RSI: ffffffff8dba9991 RDI: ffffffff8be33e00
RBP: ffffffff81ada78b R08: 0000000000000000 R09: ffffffff81ada78b
R10: dffffc0000000000 R11: ffffed1009604f51 R12: 0000000000000000
R13: ffff88804b027a98 R14: 0000000000000001 R15: 0000000000000046
FS:  00007f87650ce6c0(0000) GS:ffff8880b8613000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000002dc000 CR3: 0000000125eec000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 _raw_spin_lock_irqsave+0xa7/0xf0
 hrtimer_try_to_cancel+0x22b/0x420
 hrtimer_cancel+0x3b/0x50
 cpu_clock_event_stop+0xd9/0x130
 __perf_event_overflow+0x580/0xe40
 perf_swevent_hrtimer+0x3c5/0x550
 __hrtimer_run_queues+0x4e0/0xc60
 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:alloc_super+0x6e1/0x970
Code: c1 e8 03 42 80 3c 38 00 74 08 4c 89 ef e8 47 80 ee ff 49 8b 55 00 bf 0c 00 00 00 48 c7 c6 60 3b 99 8b e8 12 64 cb ff 49 89 c4 <4c> 8d ab 70 07 00 00 4c 89 ed 48 c1 ed 03 42 80 7c 3d 00 00 4c 8b
RSP: 0018:ffffc90004557730 EFLAGS: 00000282
RAX: ffff888020984d00 RBX: ffff888031a16000 RCX: 1ffff920008aaeb0
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffc900045575e0
RBP: 0000000000000004 R08: ffffc900045575e7 R09: 1ffff920008aaebc
R10: dffffc0000000000 R11: fffff520008aaebd R12: ffff888020984d00
R13: ffffffff8e8003a0 R14: 7fffffffffffffff R15: dffffc0000000000
 sget_fc+0x329/0xa40
 get_tree_nodev+0x2a/0x150
 vfs_get_tree+0x92/0x2b0
 fc_mount_longterm+0x1c/0x100
 mq_init_ns+0x3a1/0x510
 copy_ipcs+0x2f6/0x4f0
 create_new_namespaces+0x218/0x720
 copy_namespaces+0x438/0x4b0
 copy_process+0x1733/0x3c00
 kernel_clone+0x21e/0x840
 __x64_sys_clone+0x18b/0x1e0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f876418eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f87650cdfe8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f87643d5fa0 RCX: 00007f876418eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000008000000
RBP: 00007f8764211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f87643d6038 R14: 00007f87643d5fa0 R15: 00007fffd68d2e68
 </TASK>
