rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (10499 ticks this GP) idle=137/1 softirq=26971/26971 fqs=5211 
	(t=10500 jiffies g=42845 q=508)
NMI backtrace for cpu 1
CPU: 1 PID: 13900 Comm: syz-executor.2 Not tainted 5.7.0-rc7-next-20200529-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+0x1e6/0x221 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:165 [inline]
 rcu_dump_cpu_stacks+0x19b/0x1e5 kernel/rcu/tree_stall.h:318
 print_cpu_stall kernel/rcu/tree_stall.h:551 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:625 [inline]
 rcu_pending kernel/rcu/tree.c:3421 [inline]
 rcu_sched_clock_irq.cold+0x55a/0xd33 kernel/rcu/tree.c:2436
 update_process_times+0x25/0x60 kernel/time/timer.c:1726
 tick_sched_handle.isra.0+0x91/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x50/0x140 kernel/time/tick-sched.c:1328
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x5ca/0xea0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x312/0x770 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:719
 </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+0x207/0x260 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:576
RIP: 0010:__sanitizer_cov_trace_cmp4+0x0/0x20 kernel/kcov.c:258
Code: 66 2e 0f 1f 84 00 00 00 00 00 48 8b 0c 24 0f b7 d6 0f b7 f7 bf 02 00 00 00 e9 4c ff ff ff 66 90 66 2e 0f 1f 84 00 00 00 00 00 <48> 8b 0c 24 89 f2 89 fe bf 04 00 00 00 e9 2e ff ff ff 0f 1f 40 00
RSP: 0018:ffffc900061bf720 EFLAGS: 00000246
RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc9000d884000
RDX: 0000000000040000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88805720a0c0 R09: ffffed1010d71910
R10: ffff888086b8c87f R11: ffffed1010d7190f R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
 bvec_iter_advance include/linux/bvec.h:101 [inline]
 iov_iter_copy_from_user_atomic+0x969/0xc00 lib/iov_iter.c:1000
 generic_perform_write+0x277/0x4e0 mm/filemap.c:3345
 ext4_buffered_write_iter+0x1f7/0x450 fs/ext4/file.c:270
 ext4_file_write_iter+0x1ec/0x13f0 fs/ext4/file.c:649
 call_write_iter include/linux/fs.h:1926 [inline]
 do_iter_readv_writev+0x51e/0x790 fs/read_write.c:694
 do_iter_write fs/read_write.c:999 [inline]
 do_iter_write+0x18b/0x600 fs/read_write.c:980
 vfs_iter_write+0x70/0xa0 fs/read_write.c:1040
 iter_file_splice_write+0x695/0xb10 fs/splice.c:750
 do_splice_from+0x86/0x110 fs/splice.c:846
 do_splice+0xa96/0x14b0 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:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ca69
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f83f81ccc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00000000005084c0 RCX: 000000000045ca69
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 000000000004ffe0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000bcb R14: 00000000004cec98 R15: 00007f83f81cd6d4