INFO: task syz-executor5:9163 blocked for more than 120 seconds. Not tainted 4.9.80-g550c01d #29 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor5 D29936 9163 3913 0x00000004 ffff8801b4821800 ffff8801b52d1500 ffff8801b63e4540 ffff8801b4823000 ffff8801db221b98 ffff8801d7fd7ba8 ffffffff838a23db 0000000000000001 0000000000000007 00ff8801b4821800 ffff8801db222468 ffff8801db222490 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3550 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3583 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x312/0x870 kernel/locking/mutex.c:621 [] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1913 [] vfs_ioctl fs/ioctl.c:43 [inline] [] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679 [] SYSC_ioctl fs/ioctl.c:694 [inline] [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [] entry_SYSCALL_64_fastpath+0x29/0xe8 Showing all locks held in the system: 2 locks held by khungtaskd/515: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x125/0xa70 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336 2 locks held by getty/3786: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133 2 locks held by syz-executor5/9163: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899 #1: (&lo->lo_ctl_mutex#2){+.+...}, at: [] loop_control_ioctl+0x176/0x300 drivers/block/loop.c:1913 1 lock held by syz-executor5/9176: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899 1 lock held by syz-executor5/9188: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899 1 lock held by syz-executor5/9201: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1899 2 locks held by syz-executor0/9156: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 #1: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189 1 lock held by syz-executor0/9178: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268 1 lock held by syz-executor0/9184: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 1 lock held by syz-executor0/9190: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 2 locks held by blkid/9167: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268 #1: (loop_index_mutex){+.+.+.}, at: [] lo_open+0x1b/0xa0 drivers/block/loop.c:1548 1 lock held by syz-executor7/9205: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268 1 lock held by syz-executor7/9213: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd50 fs/block_dev.c:1268 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 515 Comm: khungtaskd Not tainted 4.9.80-g550c01d #29 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d86c7d00 ffffffff81d94b69 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ffffffff810bac60 ffff8801d86c7d38 ffffffff81d9fc8d 0000000000000000 0000000000000000 ffff8801b688e418 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6f0/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:477 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff838b20c6