INFO: task syz-executor0:4504 blocked for more than 120 seconds. Not tainted 4.16.0-rc7+ #374 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D21904 4504 4494 0x00000000 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 lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601 block_ioctl+0xde/0x120 fs/block_dev.c:1875 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: 0033:0x4550d7 RSP: 002b:0000000000a3eab8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000000002c9 RCX: 00000000004550d7 RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000013 RBP: 0000000000000013 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000013 R13: 0000000000000000 R14: 00000000006fd700 R15: 0000000000001380 Showing all locks held in the system: 2 locks held by khungtaskd/876: #0: (rcu_read_lock){....}, at: [<00000000448bb299>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000448bb299>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000009d7d8e99>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4334: #0: (&f->f_pos_lock){+.+.}, at: [<000000001e53fa89>] __fdget_pos+0x12b/0x190 fs/file.c:765 2 locks held by getty/4425: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4426: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4427: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4428: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4429: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4430: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4431: #0: (&tty->ldisc_sem){++++}, at: [<00000000681da3f5>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000006518022f>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/4504: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e6eeb6a9>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor1/31885: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e6eeb6a9>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor1/31902: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e6eeb6a9>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor1/31903: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e6eeb6a9>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor1/31905: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e6eeb6a9>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 876 Comm: khungtaskd Not tainted 4.16.0-rc7+ #374 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