INFO: rcu_sched self-detected stall on CPU
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-....: (125000 ticks this GP) idle=912/140000000000001/0 softirq=59040/59041 fqs=31247 
	(detected by 1, t=125002 jiffies, g=32654, c=32653, q=217)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 23559 Comm: syz-executor2 Not tainted 4.15.0-rc7+ #163
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:inb arch/x86/include/asm/io.h:348 [inline]
RIP: 0010:io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:434
RSP: 0018:ffff8801db206ff8 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000005 RDI: ffffffff8885ef58
RBP: ffff8801db207008 R08: 1ffff1003b640d57 R09: 000000000000000c
R10: ffff8801db206f78 R11: 0000000000000040 R12: ffffffff8885ef20
R13: 0000000000000020 R14: fffffbfff110be29 R15: fffffbfff110bded
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:00000000f7746b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007f5b4df8f000 CR3: 00000001a6e87001 CR4: 00000000001626f0
Call Trace:
 <IRQ>
 serial_in drivers/tty/serial/8250/8250.h:111 [inline]
 wait_for_xmitr+0x93/0x1e0 drivers/tty/serial/8250/8250_port.c:2033
 serial8250_console_putchar+0x1f/0x60 drivers/tty/serial/8250/8250_port.c:3170
 uart_console_write+0xac/0xe0 drivers/tty/serial/serial_core.c:1858
 serial8250_console_write+0x64f/0xa40 drivers/tty/serial/8250/8250_port.c:3236
 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590
 call_console_drivers kernel/printk/printk.c:1574 [inline]
 console_unlock+0x788/0xd80 kernel/printk/printk.c:2233
 vprintk_emit+0x4ad/0x590 kernel/printk/printk.c:1757
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1796
 vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
 printk+0xaa/0xca kernel/printk/printk.c:1829
 print_cpu_stall_info_begin kernel/rcu/tree_plugin.h:1657 [inline]
 print_cpu_stall kernel/rcu/tree.c:1594 [inline]
 check_cpu_stall.isra.61+0x845/0x15b0 kernel/rcu/tree.c:1676
 __rcu_pending kernel/rcu/tree.c:3440 [inline]
 rcu_pending kernel/rcu/tree.c:3502 [inline]
 rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
 update_process_times+0x30/0x60 kernel/time/timer.c:1628
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
 __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
 __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309
 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+0xa9/0xb0 arch/x86/entry/entry_64.S:920
 </IRQ>
RIP: 0010:loop_set_fd drivers/block/loop.c:885 [inline]
RIP: 0010:lo_ioctl+0x5de/0x1b70 drivers/block/loop.c:1358
RSP: 0018:ffff8801d4b87bd8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffffff839457db
RDX: 1ffff1003ae52afc RSI: ffffc90004de3000 RDI: ffff8801d72957e0
RBP: ffff8801d4b87c50 R08: 0000000000000000 R09: 1ffff1003a970f2c
R10: ffff8801d4b87928 R11: 0000000000000001 R12: ffff8801d7295700
R13: ffff8801d5859240 R14: ffff8801cee5a1c0 R15: ffff8801d5859390
 lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1556
 compat_blkdev_ioctl+0x3ae/0x1840 block/compat_ioctl.c:406
 C_SYSC_ioctl fs/compat_ioctl.c:1473 [inline]
 compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1419
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f4ac79
RSP: 002b:00000000f774608c EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000015 RCX: 0000000000004c00
RDX: 0000000000000013 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Code: 24 d1 00 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 17 41 03 5c 24 38 89 da ec <5b> 0f b6 c0 41 5c 5d c3 e8 08 6c 10 ff eb c2 e8 61 6c 10 ff eb 
	0-....: (125000 ticks this GP) idle=912/140000000000001/0 softirq=59040/59041 fqs=31411 
	 (t=125659 jiffies g=32654 c=32653 q=217)
NMI backtrace for cpu 0
CPU: 0 PID: 23559 Comm: syz-executor2 Not tainted 4.15.0-rc7+ #163
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
 rcu_dump_cpu_stacks+0x186/0x1d9 kernel/rcu/tree.c:1459
 print_cpu_stall kernel/rcu/tree.c:1608 [inline]
 check_cpu_stall.isra.61+0xbb8/0x15b0 kernel/rcu/tree.c:1676
 __rcu_pending kernel/rcu/tree.c:3440 [inline]
 rcu_pending kernel/rcu/tree.c:3502 [inline]
 rcu_check_callbacks+0x256/0xd00 kernel/rcu/tree.c:2842
 update_process_times+0x30/0x60 kernel/time/timer.c:1628
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
 __run_hrtimer kernel/time/hrtimer.c:1211 [inline]
 __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309
 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+0xa9/0xb0 arch/x86/entry/entry_64.S:920
 </IRQ>
RIP: 0010:loop_set_fd drivers/block/loop.c:885 [inline]
RIP: 0010:lo_ioctl+0x5de/0x1b70 drivers/block/loop.c:1358
RSP: 0018:ffff8801d4b87bd8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: 0000000000010000 RBX: dffffc0000000000 RCX: ffffffff839457db
RDX: 1ffff1003ae52afc RSI: ffffc90004de3000 RDI: ffff8801d72957e0
RBP: ffff8801d4b87c50 R08: 0000000000000000 R09: 1ffff1003a970f2c
R10: ffff8801d4b87928 R11: 0000000000000001 R12: ffff8801d7295700
R13: ffff8801d5859240 R14: ffff8801cee5a1c0 R15: ffff8801d5859390
 lo_compat_ioctl+0xab/0x140 drivers/block/loop.c:1556
 compat_blkdev_ioctl+0x3ae/0x1840 block/compat_ioctl.c:406
 C_SYSC_ioctl fs/compat_ioctl.c:1473 [inline]
 compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1419
 do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
 do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
 entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f4ac79
RSP: 002b:00000000f774608c EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000015 RCX: 0000000000004c00
RDX: 0000000000000013 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000