INFO: task syz-executor2:7731 blocked for more than 120 seconds. Not tainted 4.14.0-rc4+ #124 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor2 D20272 7731 3037 0x00000004 Call Trace: context_switch kernel/sched/core.c:2790 [inline] __schedule+0x8eb/0x2080 kernel/sched/core.c:3366 schedule+0xf5/0x430 kernel/sched/core.c:3425 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3483 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xadb/0x19d0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1601 blkdev_open+0x1e4/0x270 fs/block_dev.c:1759 do_dentry_open+0x67f/0xd70 fs/open.c:752 vfs_open+0x107/0x230 fs/open.c:866 do_last fs/namei.c:3387 [inline] path_openat+0x1157/0x3520 fs/namei.c:3527 do_filp_open+0x25b/0x3b0 fs/namei.c:3562 do_sys_open+0x502/0x6d0 fs/open.c:1059 SYSC_open fs/open.c:1077 [inline] SyS_open+0x2d/0x40 fs/open.c:1072 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x40c461 RSP: 002b:00007fc86e7a8750 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: cccccccccccccccd RCX: 000000000040c461 RDX: 0000000000000000 RSI: 0000000000000006 RDI: 00007fc86e7a8800 RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000 R10: 000000000000000c R11: 0000000000000293 R12: 0000000000000017 R13: 0000000020aad000 R14: 0000000000000006 R15: 0000000000000016 Showing all locks held in the system: 2 locks held by khungtaskd/643: #0: (rcu_read_lock){....}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4552 2 locks held by getty/2955: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 2 locks held by getty/2956: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 2 locks held by getty/2957: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 2 locks held by getty/2958: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 2 locks held by getty/2959: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 2 locks held by getty/2960: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 3 locks held by kworker/u4:4/3237: #0: ("writeback"){+.+.}, at: [] __write_once_size include/linux/compiler.h:305 [inline] #0: ("writeback"){+.+.}, at: [] atomic64_set arch/x86/include/asm/atomic64_64.h:33 [inline] #0: ("writeback"){+.+.}, at: [] atomic_long_set include/asm-generic/atomic-long.h:56 [inline] #0: ("writeback"){+.+.}, at: [] set_work_data kernel/workqueue.c:617 [inline] #0: ("writeback"){+.+.}, at: [] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ("writeback"){+.+.}, at: [] process_one_work+0xad4/0x1bd0 kernel/workqueue.c:2090 #1: ((&(&wb->dwork)->work)){+.+.}, at: [] process_one_work+0xb2c/0x1bd0 kernel/workqueue.c:2094 #2: (&type->s_umount_key#30){++++}, at: [] trylock_super+0x20/0x100 fs/super.c:391 1 lock held by syz-executor0/7749: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_put+0xa7/0x7c0 fs/block_dev.c:1767 1 lock held by syz-executor2/7731: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 1 lock held by syz-executor2/7734: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 1 lock held by syz-executor7/7750: #0: (&bdev->bd_mutex){+.+.}, at: [] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2155 1 lock held by blkid/7761: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 1 lock held by syz-executor3/7777: #0: (&bdev->bd_mutex){+.+.}, at: [] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2155 1 lock held by syz-executor3/7785: #0: (&bdev->bd_mutex){+.+.}, at: [] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2155 2 locks held by getty/7811: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2133 1 lock held by syz-executor0/7831: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 1 lock held by syz-executor0/7833: #0: (&bdev->bd_mutex){+.+.}, at: [] __blkdev_get+0x158/0xf90 fs/block_dev.c:1449 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 643 Comm: khungtaskd Not tainted 4.14.0-rc4+ #124 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 nmi_cpu_backtrace+0x20e/0x240 lib/nmi_backtrace.c:102 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:61 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 trigger_all_cpu_backtrace include/linux/nmi.h:137 [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+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff84d412c6