loop5: p1 p2 p3 p4
 loop5: p1 p2 p3 p4
INFO: task syz-executor.5:18109 blocked for more than 140 seconds.
      Not tainted 4.9.170+ #45
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D25768 18109  18108 0x00000000
 ffff8801a077df00 ffff8801d137dd80 ffff8801db621000 ffff8801a1745f00
 ffff8801db621018 ffff880186aaf988 ffffffff8280185e 0000000000000000
 ffffffff830c1d40 00ff880186aaf9b0 ffff8801db6218f0 1ffff10030d55f20
Call Trace:
 [<00000000cac09831>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<000000008d5bd64c>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<000000007e5b08f3>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<000000007e5b08f3>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<0000000021614eea>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
 [<000000004dade6e8>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:638
 [<0000000042cc50ed>] loop_clr_fd+0x7dd/0xa60 drivers/block/loop.c:1082
 [<0000000047a46d49>] lo_ioctl+0x7b6/0x1a10 drivers/block/loop.c:1415
 [<000000001f6aac9a>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<000000001f6aac9a>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590
 [<00000000d87c4936>] block_ioctl+0xde/0x120 fs/block_dev.c:1696
 [<000000007627ffcd>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<000000007627ffcd>] file_ioctl fs/ioctl.c:493 [inline]
 [<000000007627ffcd>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677
 [<000000005e12b743>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<000000005e12b743>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<000000000c11bd92>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<00000000428d55b4>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<0000000075ece0ae>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<0000000075ece0ae>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<000000009d5aa3d5>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
2 locks held by getty/2020:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000e3be0b4e>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<000000002c827031>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.5/18109:
 #0:  (loop_ctl_mutex/1){+.+.+.}, at: [<000000004c047520>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000021614eea>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
1 lock held by syz-executor.0/31607:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000cabf3a17>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629
2 locks held by syz-executor.0/5225:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000023d6106f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a8b44c42>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
3 locks held by syz-executor.4/5252:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000001daa175f>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000fd6f8dd9>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<0000000044f233e2>] __lo_release drivers/block/loop.c:1642 [inline]
 #2:  (loop_ctl_mutex#2){+.+.+.}, at: [<0000000044f233e2>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665
2 locks held by blkid/5268:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000023d6106f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a8b44c42>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #45
 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000001 0000000000000000
 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b5adbc 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<000000002a0d71b8>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000002a0d71b8>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<000000007255d57c>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<000000001d71585a>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<0000000009fb3409>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<0000000090aa0b19>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<0000000090aa0b19>] check_hung_task kernel/hung_task.c:126 [inline]
 [<0000000090aa0b19>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<0000000090aa0b19>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<000000006306541b>] kthread+0x278/0x310 kernel/kthread.c:211
 [<0000000088403b33>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff828108d2