INFO: task syz-executor1:26825 blocked for more than 120 seconds. Not tainted 4.15.0-rc3-next-20171214+ #67 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D 0 26825 3396 0x00000004 Call Trace: context_switch kernel/sched/core.c:2800 [inline] __schedule+0x30b/0xaf0 kernel/sched/core.c:3376 schedule+0x2e/0x90 kernel/sched/core.c:3435 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3493 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x466/0xa00 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x1b/0x60 drivers/block/loop.c:1571 __blkdev_get+0x4cf/0x660 fs/block_dev.c:1516 blkdev_get+0x196/0x450 fs/block_dev.c:1591 blkdev_open+0xc0/0xf0 fs/block_dev.c:1749 do_dentry_open+0x282/0x410 fs/open.c:752 vfs_open+0x5d/0xb0 fs/open.c:866 do_last fs/namei.c:3397 [inline] path_openat+0x24c/0x1050 fs/namei.c:3537 do_filp_open+0xaa/0x120 fs/namei.c:3572 do_sys_open+0x280/0x340 fs/open.c:1059 SYSC_open fs/open.c:1077 [inline] SyS_open+0x2d/0x40 fs/open.c:1072 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x40cd71 RSP: 002b:00007f20b88e9780 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 000000000040cd71 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f20b88e9830 RBP: 0000000000000249 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000207d3000 R11: 0000000000000293 R12: 00000000006f1778 R13: 00000000ffffffff R14: 00007f20b88ea6d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/674: #0: (rcu_read_lock){....}, at: [<00000000701aa11a>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000701aa11a>] watchdog+0xbf/0x750 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000048d3cb51>] debug_show_all_locks+0x3d/0x1a0 kernel/locking/lockdep.c:4464 1 lock held by rsyslogd/3006: #0: (&f->f_pos_lock){+.+.}, at: [<00000000dbf4b770>] __fdget_pos+0x5b/0x70 fs/file.c:765 2 locks held by getty/3129: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by getty/3130: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by getty/3131: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by getty/3132: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by getty/3133: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by getty/3134: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 2 locks held by syz-executor1/26825: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000b651e965>] __blkdev_get+0x80/0x660 fs/block_dev.c:1439 #1: (loop_index_mutex){+.+.}, at: [<00000000dc9a11e4>] lo_open+0x1b/0x60 drivers/block/loop.c:1571 2 locks held by syz-executor6/26830: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 #1: (&lo->lo_ctl_mutex#2){+.+.}, at: [<0000000017c55903>] loop_control_ioctl+0xe4/0x1a0 drivers/block/loop.c:1946 1 lock held by syz-executor6/26836: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 1 lock held by syz-executor6/26861: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 1 lock held by syz-executor6/26866: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 2 locks held by syz-executor4/26838: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<0000000058c9fe8c>] lo_ioctl+0x44/0xa40 drivers/block/loop.c:1355 #1: (&bdev->bd_mutex){+.+.}, at: [<00000000a14ac85a>] blkdev_reread_part+0x1e/0x40 block/ioctl.c:192 1 lock held by syz-executor4/26853: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000b651e965>] __blkdev_get+0x80/0x660 fs/block_dev.c:1439 1 lock held by syz-executor4/26858: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<0000000058c9fe8c>] lo_ioctl+0x44/0xa40 drivers/block/loop.c:1355 1 lock held by syz-executor4/26863: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<0000000058c9fe8c>] lo_ioctl+0x44/0xa40 drivers/block/loop.c:1355 1 lock held by syz-executor3/26839: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 1 lock held by syz-executor3/26849: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 1 lock held by syz-executor3/26860: #0: (loop_index_mutex){+.+.}, at: [<00000000cf288d76>] loop_control_ioctl+0x25/0x1a0 drivers/block/loop.c:1932 2 locks held by getty/26882: #0: (&tty->ldisc_sem){++++}, at: [<0000000008b98074>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000009833cefb>] n_tty_read+0xce/0xa40 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 674 Comm: khungtaskd Not tainted 4.15.0-rc3-next-20171214+ #67 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+0xe9/0x14b lib/dump_stack.c:53 nmi_cpu_backtrace+0x149/0x150 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x101/0x150 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+0x562/0x750 kernel/hung_task.c:249 kthread+0x149/0x170 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54