INFO: rcu_sched self-detected stall on CPU
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-....: (125000 ticks this GP) idle=3fe/1/4611686018427387906 softirq=23451/23451 fqs=31223 
	(detected by 1, t=125002 jiffies, g=12201, c=12200, q=865)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8045 Comm: syz-executor7 Not tainted 4.14.0-rc5-mm1+ #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b7a440 task.stack: ffff8801c1560000
RIP: 0010:outb arch/x86/include/asm/io.h:308 [inline]
RIP: 0010:io_serial_out+0x73/0x90 drivers/tty/serial/8250/8250_port.c:444
RSP: 0018:ffff8801db207040 EFLAGS: 00000002
RAX: 0000000000000035 RBX: 00000000000003f8 RCX: 0000000000000000
RDX: 00000000000003f8 RSI: 0000000000000000 RDI: ffffffff8788b458
RBP: ffff8801db207058 R08: ffffffff82875f96 R09: 000000000000000c
R10: ffff8801db206f78 R11: 0000000000000040 R12: ffffffff8788b420
R13: 0000000000000035 R14: dffffc0000000000 R15: 0000000000000035
FS:  00007f8f440b8700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001fe8 CR3: 00000001b3f65000 CR4: 00000000001426f0
DR0: 0000000020001000 DR1: 0000000020001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 serial_port_out include/linux/serial_core.h:265 [inline]
 serial8250_console_putchar+0x45/0x60 drivers/tty/serial/8250/8250_port.c:3175
 uart_console_write+0xac/0xe0 drivers/tty/serial/serial_core.c:1872
 serial8250_console_write+0x647/0xa20 drivers/tty/serial/8250/8250_port.c:3240
 univ8250_console_write+0x64/0x80 drivers/tty/serial/8250/8250_core.c:596
 call_console_drivers kernel/printk/printk.c:1693 [inline]
 console_unlock+0x788/0xd70 kernel/printk/printk.c:2351
 vprintk_emit+0x4ad/0x590 kernel/printk/printk.c:1876
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1915
 vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
 printk+0xaa/0xca kernel/printk/printk.c:1948
 print_cpu_stall_info_begin kernel/rcu/tree_plugin.h:1656 [inline]
 print_cpu_stall kernel/rcu/tree.c:1512 [inline]
 check_cpu_stall.isra.65+0x845/0x15b0 kernel/rcu/tree.c:1594
 __rcu_pending kernel/rcu/tree.c:3358 [inline]
 rcu_pending kernel/rcu/tree.c:3420 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2760
 update_process_times+0x30/0x60 kernel/time/timer.c:1590
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1192
 __run_hrtimer kernel/time/hrtimer.c:1213 [inline]
 __hrtimer_run_queues+0x349/0xe10 kernel/time/hrtimer.c:1277
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1311
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:770
 </IRQ>
RIP: 0010:loop_set_fd drivers/block/loop.c:882 [inline]
RIP: 0010:lo_ioctl+0x5af/0x1b70 drivers/block/loop.c:1358
RSP: 0018:ffff8801c1567aa0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffffff8365cedc
RDX: 1ffff1003a2c18dc RSI: ffffc90002e5b000 RDI: ffff8801d160c6e0
RBP: ffff8801c1567b18 R08: 0000000000000001 R09: 1ffff100382acf05
R10: ffff8801c15677f0 R11: 0000000000000001 R12: ffff8801d160c358
R13: ffff8801d62836c0 R14: ffff8801d161e180 R15: ffff8801d6283810
 __blkdev_driver_ioctl block/ioctl.c:297 [inline]
 blkdev_ioctl+0xc07/0x1de0 block/ioctl.c:594
 block_ioctl+0xde/0x120 fs/block_dev.c:1860
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x452869
RSP: 002b:00007f8f440b7be8 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452869
RDX: 0000000000000015 RSI: 0000000000004c00 RDI: 0000000000000014
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ee928
R13: 00000000ffffffff R14: 00007f8f440b86d4 R15: 0000000000000000
Code: 00 00 49 8d 7c 24 38 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 d3 e3 80 3c 02 00 75 19 41 03 5c 24 38 44 89 e8 89 da ee <5b> 41 5c 41 5d 5d c3 e8 d1 ad 1d ff eb c0 e8 2a ae 1d ff eb e0 
	0-....: (125000 ticks this GP) idle=3fe/1/4611686018427387906 softirq=23451/23451 fqs=31383 
	 (t=125651 jiffies g=12201 c=12200 q=865)
NMI backtrace for cpu 0
CPU: 0 PID: 8045 Comm: syz-executor7 Not tainted 4.14.0-rc5-mm1+ #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 nmi_cpu_backtrace+0x20e/0x240 lib/nmi_backtrace.c:102
 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:61
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 trigger_single_cpu_backtrace include/linux/nmi.h:155 [inline]
 rcu_dump_cpu_stacks+0x186/0x1da kernel/rcu/tree.c:1377
 print_cpu_stall kernel/rcu/tree.c:1526 [inline]
 check_cpu_stall.isra.65+0xbb8/0x15b0 kernel/rcu/tree.c:1594
 __rcu_pending kernel/rcu/tree.c:3358 [inline]
 rcu_pending kernel/rcu/tree.c:3420 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2760
 update_process_times+0x30/0x60 kernel/time/timer.c:1590
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1192
 __run_hrtimer kernel/time/hrtimer.c:1213 [inline]
 __hrtimer_run_queues+0x349/0xe10 kernel/time/hrtimer.c:1277
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1311
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:770
 </IRQ>
RIP: 0010:loop_set_fd drivers/block/loop.c:882 [inline]
RIP: 0010:lo_ioctl+0x5af/0x1b70 drivers/block/loop.c:1358
RSP: 0018:ffff8801c1567aa0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffffff8365cedc
RDX: 1ffff1003a2c18dc RSI: ffffc90002e5b000 RDI: ffff8801d160c6e0
RBP: ffff8801c1567b18 R08: 0000000000000001 R09: 1ffff100382acf05
R10: ffff8801c15677f0 R11: 0000000000000001 R12: ffff8801d160c358
R13: ffff8801d62836c0 R14: ffff8801d161e180 R15: ffff8801d6283810
 __blkdev_driver_ioctl block/ioctl.c:297 [inline]
 blkdev_ioctl+0xc07/0x1de0 block/ioctl.c:594
 block_ioctl+0xde/0x120 fs/block_dev.c:1860
 vfs_ioctl fs/ioctl.c:45 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
 SYSC_ioctl fs/ioctl.c:700 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x452869
RSP: 002b:00007f8f440b7be8 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452869
RDX: 0000000000000015 RSI: 0000000000004c00 RDI: 0000000000000014
RBP: 0000000000000082 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ee928
R13: 00000000ffffffff R14: 00007f8f440b86d4 R15: 0000000000000000