INFO: task syz-executor.0:2105 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #17
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D ffff8801c28275d8 24960  2105      1 0x20020004
 ffff8801c28275d8 ffff8800b248c740 783b3fd1c76750e6 ffff8800b248c740
 0000000000000001 ffff8800b248d000 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8801d3e8c740 ffff8800b248c740 ffffed0038504001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff81d3d70d>] lo_open+0x1d/0xb0 drivers/block/loop.c:1633
 [<ffffffff8154f171>] __blkdev_get+0x8b1/0xdf0 fs/block_dev.c:1278
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
2 locks held by syz-executor.0/2105:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff8154e9cc>] __blkdev_get+0x10c/0xdf0 fs/block_dev.c:1199
 #1:  (loop_index_mutex){+.+.+.}, at: [<ffffffff81d3d70d>] lo_open+0x1d/0xb0 drivers/block/loop.c:1633
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #17
task: ffff8801da6c4740 task.stack: ffff8801d9ef0000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8801d9ef7c88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8801d9ef7cb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001571000 CR3: 00000000b9073000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8801d9ef7cd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8801d9ef7d30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1 
NMI backtrace for cpu 1
CPU: 1 PID: 1923 Comm: rsyslogd Not tainted 4.4.174+ #17
task: ffff8800b8cd0000 task.stack: ffff8801d6478000
RIP: 0010:[<ffffffff811ffc14>]  [<ffffffff811ffc14>] __lock_acquire+0x664/0x4f50 kernel/locking/lockdep.c:3119
RSP: 0018:ffff8801d647f8c0  EFLAGS: 00000002
RAX: 0000000000000000 RBX: ffffffff83ad05d0 RCX: 1ffffffff05d4290
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: ffffffff82ea1480
RBP: ffff8801d647fa38 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff82836880 R11: ffffffff831a5078 R12: ffff8800b8cd0000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007feddabee700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffeb7cf5000 CR3: 00000000b90a9000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b8cd0910 ffff880100000001 ffff880100000000 ffffffff83a7f5d0
 ffff8800b8cd08c8 1ffff1003ac8ff20 ffff880100000001 ffff8800b8cd08b8
 0000000041b58ab3 ffffffff82c4d560 ffffffff811ff5b0 0000000000000001
Call Trace:
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82717e50>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
 [<ffffffff82717e50>] _raw_spin_lock_irqsave+0x50/0x70 kernel/locking/spinlock.c:159
 [<ffffffff811ea2e8>] prepare_to_wait_event+0x108/0x660 kernel/sched/wait.c:209
 [<ffffffff8121ef7b>] do_syslog kernel/printk/printk.c:1332 [inline]
 [<ffffffff8121ef7b>] do_syslog+0x55b/0xaf0 kernel/printk/printk.c:1306
 [<ffffffff81608274>] kmsg_read+0x74/0xa0 fs/proc/kmsg.c:39
 [<ffffffff815e03bd>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
 [<ffffffff81496556>] __vfs_read+0x116/0x3c0 fs/read_write.c:434
 [<ffffffff81498264>] vfs_read+0x134/0x360 fs/read_write.c:456
 [<ffffffff8149aa8c>] SYSC_read fs/read_write.c:571 [inline]
 [<ffffffff8149aa8c>] SyS_read+0xdc/0x1c0 fs/read_write.c:564
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 48 c1 e9 03 80 3c 11 00 0f 85 6f 33 00 00 48 8b 9c 24 88 00 00 00 48 8b 5c c3 08 48 85 db 0f 84 40 1f 00 00 f0 ff 83 98 01 00 00 <49> 8d 84 24 c0 08 00 00 48 89 c2 48 89 44 24 48 48 b8 00 00 00