INFO: task syz-executor2:12182 blocked for more than 120 seconds. Not tainted 4.15.0-rc9+ #278 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor2 D24744 12182 3715 0x00000004 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 blk_mq_freeze_queue_wait+0x1bb/0x400 block/blk-mq.c:137 blk_freeze_queue+0x4a/0x80 block/blk-mq.c:166 blk_mq_freeze_queue+0x15/0x20 block/blk-mq.c:175 loop_change_fd drivers/block/loop.c:667 [inline] lo_ioctl+0x10ce/0x1b70 drivers/block/loop.c:1361 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601 block_ioctl+0xde/0x120 fs/block_dev.c:1860 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 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x452f19 RSP: 002b:00007f58253b2c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19 RDX: 0000000000000013 RSI: 0000000000004c06 RDI: 0000000000000013 RBP: 00000000000005c3 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7ae8 R13: 00000000ffffffff R14: 00007f58253b36d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/747: #0: (rcu_read_lock){....}, at: [<0000000065fd0e63>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<0000000065fd0e63>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000059db7090>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 2 locks held by getty/3632: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3633: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3634: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3635: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3636: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3637: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor2/12182: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bd7c0dff>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor2/12205: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bd7c0dff>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor3/12192: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bd7c0dff>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 2 locks held by getty/12222: #0: (&tty->ldisc_sem){++++}, at: [<00000000dd1908e7>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000fe293cef>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 747 Comm: khungtaskd Not tainted 4.15.0-rc9+ #278 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+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 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:541 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54