INFO: task syz-executor6:10459 blocked for more than 120 seconds. Not tainted 4.16.0-rc7+ #5 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D23824 10459 6232 0x00000004 Call Trace: context_switch kernel/sched/core.c:2862 [inline] __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440 schedule+0xf5/0x430 kernel/sched/core.c:3499 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3557 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 loop_control_ioctl+0x1a7/0x490 drivers/block/loop.c:1952 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4548b9 RSP: 002b:00007fd567f30c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fd567f316d4 RCX: 00000000004548b9 RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000013 RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000027f R14: 00000000006f5c88 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/868: #0: (rcu_read_lock){....}, at: [<0000000007452a32>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<0000000007452a32>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000fc922a89>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4396: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4397: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4398: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4399: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4400: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4401: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4402: #0: (&tty->ldisc_sem){++++}, at: [<000000003d8ad9e0>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ef1144cd>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by syz-executor6/10459: #0: (loop_index_mutex){+.+.}, at: [<000000009a81f16a>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 #1: (&lo->lo_ctl_mutex#2){+.+.}, at: [<000000000975d163>] loop_control_ioctl+0x1a7/0x490 drivers/block/loop.c:1952 1 lock held by syz-executor6/10463: #0: (loop_index_mutex){+.+.}, at: [<000000009a81f16a>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 2 locks held by syz-executor0/10462: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000a9abe45f>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 #1: (&bdev->bd_mutex){+.+.}, at: [<0000000078f42d1e>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 2 locks held by syz-executor5/10470: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000df693f02>] __blkdev_get+0x176/0x13b0 fs/block_dev.c:1458 #1: (loop_index_mutex){+.+.}, at: [<00000000593149c9>] lo_open+0x1b/0xa0 drivers/block/loop.c:1571 1 lock held by blkid/10468: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000df693f02>] __blkdev_get+0x176/0x13b0 fs/block_dev.c:1458 1 lock held by syz-executor3/10476: #0: (loop_index_mutex){+.+.}, at: [<000000009a81f16a>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 1 lock held by syz-executor3/10483: #0: (loop_index_mutex){+.+.}, at: [<000000009a81f16a>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 1 lock held by syz-executor3/10485: #0: (loop_index_mutex){+.+.}, at: [<000000009a81f16a>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1938 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 868 Comm: khungtaskd Not tainted 4.16.0-rc7+ #5 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x123/0x180 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54