rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10498 ticks this GP) idle=646/1/0x4000000000000000 softirq=63869/63869 fqs=13 
	(t=10501 jiffies g=84497 q=427)
rcu: rcu_preempt kthread starved for 10476 jiffies! g84497 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:
rcu_preempt     R  running task    29664    10      2 0x00004000
Call Trace:
 context_switch kernel/sched/core.c:3458 [inline]
 __schedule+0x91f/0x2250 kernel/sched/core.c:4215
 schedule+0xd0/0x2a0 kernel/sched/core.c:4290
 schedule_timeout+0x148/0x250 kernel/time/timer.c:1908
 rcu_gp_fqs_loop kernel/rcu/tree.c:1874 [inline]
 rcu_gp_kthread+0xae5/0x1b50 kernel/rcu/tree.c:2044
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
NMI backtrace for cpu 0
CPU: 0 PID: 12990 Comm: syz-executor633 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x194/0x1cf kernel/rcu/tree_stall.h:320
 print_cpu_stall kernel/rcu/tree_stall.h:553 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:627 [inline]
 rcu_pending kernel/rcu/tree.c:3489 [inline]
 rcu_sched_clock_irq.cold+0x5b3/0xccc kernel/rcu/tree.c:2504
 update_process_times+0x25/0x60 kernel/time/timer.c:1737
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x108/0x290 kernel/time/tick-sched.c:1320
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x1d5/0xfc0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646
 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:711
 </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+0xe0/0x120 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
RIP: 0010:iov_iter_copy_from_user_atomic+0x4fa/0xbe0 lib/iov_iter.c:1000
Code: 89 44 24 40 0f 84 ca 01 00 00 49 be 00 00 00 00 00 fc ff df 48 c1 e8 03 4c 01 f0 48 89 44 24 28 e8 fb d3 dd fd 48 8b 44 24 28 <80> 38 00 0f 85 e5 05 00 00 48 8b 04 24 44 89 eb 4c 8b 60 18 48 89
RSP: 0018:ffffc9000accf6f0 EFLAGS: 00000293
RAX: fffff52001599f90 RBX: 0000000000000016 RCX: ffffffff8395ea3c
RDX: ffff8880a7aaa040 RSI: ffffffff8395e895 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff88808488ab3f
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a01bb800
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
 generic_perform_write+0x277/0x4f0 mm/filemap.c:3326
 ext4_buffered_write_iter+0x235/0x4a0 fs/ext4/file.c:270
 ext4_file_write_iter+0x1f3/0x13d0 fs/ext4/file.c:655
 call_write_iter include/linux/fs.h:1908 [inline]
 do_iter_readv_writev+0x567/0x780 fs/read_write.c:713
 do_iter_write+0x188/0x5f0 fs/read_write.c:1018
 vfs_iter_write+0x70/0xa0 fs/read_write.c:1059
 iter_file_splice_write+0x721/0xbe0 fs/splice.c:750
 do_splice_from fs/splice.c:846 [inline]
 do_splice+0xbcd/0x1820 fs/splice.c:1144
 __do_sys_splice fs/splice.c:1419 [inline]
 __se_sys_splice fs/splice.c:1401 [inline]
 __x64_sys_splice+0x198/0x250 fs/splice.c:1401
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x447409
Code: Bad RIP value.
RSP: 002b:00007f5b2200cda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000006dcc48 RCX: 0000000000447409
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006dcc40 R08: 0000000000010005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc4c
R13: 00007ffd96eff08f R14: 00007f5b2200d9c0 R15: 0000000000000000
NMI backtrace for cpu 0
CPU: 0 PID: 12990 Comm: syz-executor633 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:check_kcov_mode kernel/kcov.c:163 [inline]
RIP: 0010:write_comp_data+0x13/0x80 kernel/kcov.c:218
Code: 48 8b 80 f8 13 00 00 c3 0f 1f 44 00 00 66 2e 0f 1f 84 00 00 00 00 00 49 89 f2 65 8b 05 e6 46 8e 7e 65 48 8b 34 25 00 ff 01 00 <a9> 00 01 ff 00 74 0f f6 c4 01 74 59 8b 86 04 14 00 00 85 c0 74 4f
RSP: 0018:ffffc9000accf6e8 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff8395e9cb
RDX: 0000000000000000 RSI: ffff8880a7aaa040 RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff88808488ab3f
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a01bb800