INFO: task syz-executor7:11858 blocked for more than 120 seconds. Not tainted 4.9.77-ge12a9c4 #18 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor7 D28064 11858 5006 0x00000104 ffff8801ce7a9800 ffff8801d9529f80 ffff8801d5be5f80 ffff8801cec70000 ffff8801db221b98 ffff8801ce777670 ffffffff838a1b9b 0000000041b58ab3 ffffffff84193178 00ffffff8123bda0 ffff8801db222468 ffff8801db222490 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3550 [] schedule_timeout+0x56c/0x10b0 kernel/time/timer.c:1768 [] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5172 [] do_wait_for_common kernel/sched/completion.c:75 [inline] [] __wait_for_common kernel/sched/completion.c:93 [inline] [] wait_for_common_io kernel/sched/completion.c:107 [inline] [] wait_for_completion_io+0x20e/0x2e0 kernel/sched/completion.c:155 [] submit_bio_wait+0x11b/0x180 block/bio.c:885 [] blkdev_issue_flush+0x157/0x220 block/blk-flush.c:518 [] blkdev_fsync+0x85/0xb0 fs/block_dev.c:378 [] vfs_fsync_range+0x10a/0x250 fs/sync.c:195 [] vfs_fsync+0x29/0x30 fs/sync.c:209 [] __loop_update_dio+0x453/0x5d0 drivers/block/loop.c:207 [] loop_set_dio drivers/block/loop.c:1323 [inline] [] lo_ioctl+0x13a2/0x1990 drivers/block/loop.c:1377 [] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [] blkdev_ioctl+0x4aa/0x1a60 block/ioctl.c:590 [] block_ioctl+0xde/0x120 fs/block_dev.c:1688 [] vfs_ioctl fs/ioctl.c:43 [inline] [] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679 [] SYSC_ioctl fs/ioctl.c:694 [inline] [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [] do_syscall_64+0x197/0x490 arch/x86/entry/common.c:280 [] entry_SYSCALL64_slow_path+0x25/0x25 Showing all locks held in the system: 2 locks held by khungtaskd/514: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x125/0xa70 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336 2 locks held by getty/3311: #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+0x1f4/0x16c0 drivers/tty/n_tty.c:2133 1 lock held by syz-executor7/11858: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 1 lock held by syz-executor7/11873: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.77-ge12a9c4 #18 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d89bfd00 ffffffff81d941c9 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810babe0 ffff8801d89bfd38 ffffffff81d9f2ed 0000000000000001 0000000000000000 ffff8801ce6a4c18 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x117/0x190 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+0x6f0/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x59/0x70 arch/x86/entry/entry_64.S:466 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838b1886