INFO: task syz-executor6:28919 blocked for more than 120 seconds. Not tainted 4.9.98-g9731a2d #19 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D26728 28919 20765 0x00000004 ffff8801d3288000 ffff8801aed10000 ffff88019b1a0540 ffff8801a4f2e000 ffff8801db321b98 ffff8801ab07fb48 ffffffff839e377d ffffffff849814c8 0000000000000246 ffffffff85b2d700 00fffc0000000000 ffff8801db322468 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3557 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621 [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906 [] vfs_ioctl fs/ioctl.c:43 [inline] [] file_ioctl fs/ioctl.c:493 [inline] [] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677 [] SYSC_ioctl fs/ioctl.c:694 [inline] [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/519: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11c/0xa20 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336 2 locks held by getty/3772: #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+0x202/0x16e0 drivers/tty/n_tty.c:2133 1 lock held by syz-executor6/28919: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906 1 lock held by syz-executor6/28945: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906 2 locks held by syz-executor1/28924: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344 #1: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189 2 locks held by syz-executor0/28922: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344 #1: (&bdev->bd_mutex){+.+.+.}, at: [] blkdev_reread_part+0x1e/0x40 block/ioctl.c:189 2 locks held by syz-executor2/28929: #0: (loop_index_mutex){+.+.+.}, at: [] loop_control_ioctl+0x7a/0x300 drivers/block/loop.c:1906 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [] loop_control_ioctl+0x186/0x300 drivers/block/loop.c:1920 2 locks held by blkid/28936: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268 #1: (loop_index_mutex){+.+.+.}, at: [] lo_open+0x1b/0xa0 drivers/block/loop.c:1555 2 locks held by blkid/28937: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xd60 fs/block_dev.c:1268 #1: (loop_index_mutex){+.+.+.}, at: [] lo_open+0x1b/0xa0 drivers/block/loop.c:1555 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.98-g9731a2d #19 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d9057d08 ffffffff81eb0ee9 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ffffffff810b7da0 ffff8801d9057d40 ffffffff81ebc1e7 0000000000000000 0000000000000000 0000000000000003 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x12a/0x14f 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+0x6b4/0xa20 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff839f3286