INFO: task syz-executor0:24039 blocked for more than 120 seconds. Not tainted 4.9.107-gdb2c520 #49 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D29512 24039 3735 0x00000004 ffff88019bc4b000 0000000000000000 ffff8801cd3fe4c0 ffff88019bc49800 ffff8801db321c18 ffff8801d4a9f9f0 ffffffff839e8c1d 0000000000000002 0000000041b58ab3 ffffffff843b9ea3 00ffffff81221500 ffff8801db3224e8 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3557 [] blk_mq_freeze_queue_wait+0x114/0x230 block/blk-mq.c:75 [] blk_freeze_queue block/blk-mq.c:92 [inline] [] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:101 [] loop_switch drivers/block/loop.c:599 [inline] [] loop_change_fd drivers/block/loop.c:685 [inline] [] lo_ioctl+0x722/0x1aa0 drivers/block/loop.c:1350 [] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590 [] block_ioctl+0xde/0x120 fs/block_dev.c:1688 [] 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 1 lock held by rsyslogd/3568: #0: (&f->f_pos_lock){+.+.+.}, at: [] __fdget_pos+0xac/0xd0 fs/file.c:781 2 locks held by getty/3664: #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-executor0/24039: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344 1 lock held by blkid/24138: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.107-gdb2c520 #49 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d85f7d08 ffffffff81eb3da9 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810b96a0 ffff8801d85f7d40 ffffffff81ebf0a7 0000000000000001 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 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff839f8726