rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=409c/1/0x4000000000000000 softirq=19521/19521 fqs=15
rcu: 	(detected by 1, t=10506 jiffies, g=12745, q=288 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6691 Comm: syz.0.233 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:validate_chain+0x1e1/0x2140
Code: cc 48 ff cb f7 c1 00 60 00 00 74 c8 e9 8d 00 00 00 48 c7 c7 90 b1 00 8e 4c 89 fe e8 19 83 62 03 48 8b 14 24 eb c9 48 8b 48 18 <4c> 39 f9 0f 84 b2 00 00 00 48 8b 40 08 48 85 c0 0f 84 c2 fe ff ff
RSP: 0018:ffffc90000007638 EFLAGS: 00000046
RAX: ffffffff93ae7e10 RBX: 000000000002c50a RCX: 473ffccf9dd79c24
RDX: 0000000000000000 RSI: ffff888107efe158 RDI: ffff888107efd640
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff81ada78b
R10: dffffc0000000000 R11: ffffed1009604f51 R12: 0000000000000001
R13: ffff888107efe130 R14: ffff888107efe158 R15: d6bf87c490213bdc
FS:  00007f802a4c26c0(0000) GS:ffff8880b8612000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0b8395dd58 CR3: 0000000028836000 CR4: 00000000000006f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 _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:lock_acquire+0x175/0x360
Code: 00 00 00 00 9c 8f 44 24 30 f7 44 24 30 00 02 00 00 0f 85 cd 00 00 00 f7 44 24 08 00 02 00 00 74 01 fb 65 48 8b 05 7b 6f 03 11 <48> 3b 44 24 58 0f 85 f2 00 00 00 48 83 c4 60 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc9000664fc50 EFLAGS: 00000206
RAX: f142cfa63215f700 RBX: 0000000000000000 RCX: f142cfa63215f700
RDX: 0000000000000000 RSI: ffffffff8dbaa0c3 RDI: ffffffff8be34280
RBP: ffffffff81f0579c R08: 0000000000000000 R09: ffffffff81f0579c
R10: dffffc0000000000 R11: ffffed1004226999 R12: 0000000000000002
R13: ffffffff99b156b0 R14: 0000000000000001 R15: 0000000000000246
 class_srcu_constructor+0x4b/0x60
 __se_sys_perf_event_open+0x493/0x1d70
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f802958ec29
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:00007f802a4c2038 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007f80297d6090 RCX: 00007f802958ec29
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000180
RBP: 00007f8029611e41 R08: 000000000000000a R09: 0000000000000000
R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007f80297d6128 R14: 00007f80297d6090 R15: 00007ffd7c1fa298
 </TASK>
rcu: rcu_preempt kthread starved for 10430 jiffies! g12745 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: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+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 1272 Comm: kworker/1:2 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
Workqueue: events fqdir_free_fn
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x70
Code: 8b 3d 94 73 fe 0b 48 89 de 5b e9 13 21 59 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0c 25 08 e0 a0 92 65 8b 15 b8 1e e1 10 81 e2 00 01 ff 00
RSP: 0018:ffffc900078378b8 EFLAGS: 00000202
RAX: ffffffff81b44b4f RBX: ffffc90007837908 RCX: ffff888108b75640
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900078379b8 R08: ffffc90007837767 R09: 1ffff92000f06eec
R10: dffffc0000000000 R11: fffff52000f06eed R12: 1ffff92000f06f21
R13: dffffc0000000000 R14: 1ffff92000f06f1c R15: 1ffff92000f06f1c
FS:  0000000000000000(0000) GS:ffff8881a3c12000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0b8395cfc8 CR3: 0000000025836000 CR4: 00000000000006f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 smp_call_function_single+0x3bf/0x590
 rcu_barrier+0x360/0x570
 fqdir_free_fn+0x33/0x140
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
