INFO: task syz-executor6:11436 blocked for more than 120 seconds. Not tainted 4.15.0+ #286 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D25520 11436 4253 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:136 blk_freeze_queue+0x4a/0x80 block/blk-mq.c:165 blk_mq_freeze_queue+0x15/0x20 block/blk-mq.c:174 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: 0033:0x453299 RSP: 002b:00007f76ce6f2c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299 RDX: 0000000000000013 RSI: 0000000000004c06 RDI: 0000000000000013 RBP: 000000000000061d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f8358 R13: 00000000ffffffff R14: 00007f76ce6f36d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/759: #0: (rcu_read_lock){....}, at: [<0000000059b8cc01>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<0000000059b8cc01>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000006add4a31>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4465 1 lock held by rsyslogd/4048: #0: (&f->f_pos_lock){+.+.}, at: [<00000000e09fdd05>] __fdget_pos+0x12b/0x190 fs/file.c:770 2 locks held by getty/4172: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4173: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4174: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4175: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4176: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4177: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/32675: #0: (&tty->ldisc_sem){++++}, at: [<000000002f77f454>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000089febd25>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor6/11436: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000004c4a3539>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor6/11449: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000004c4a3539>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by blkid/11478: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000004c4a3539>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 759 Comm: khungtaskd Not tainted 4.15.0+ #286 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:542 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