------------[ cut here ]------------ kobject: 'loop4' (00000000c90d1462): kobject_uevent_env kobject: 'loop4' (00000000c90d1462): fill_kobj_path: path = '/devices/virtual/block/loop4' ODEBUG: free active (active state 1) object type: rcu_head hint: (null) WARNING: CPU: 0 PID: 21 at lib/debugobjects.c:329 debug_print_object+0x16a/0x210 lib/debugobjects.c:326 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 21 Comm: kworker/u4:1 Not tainted 4.19.0-rc7-next-20181015+ #94 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 panic+0x2ad/0x55c kernel/panic.c:188 __warn.cold.8+0x20/0x45 kernel/panic.c:540 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 RIP: 0010:debug_print_object+0x16a/0x210 lib/debugobjects.c:326 Code: 41 88 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 92 00 00 00 48 8b 14 dd 80 08 41 88 4c 89 fe 48 c7 c7 20 fe 40 88 e8 36 c3 b3 fd <0f> 0b 83 05 b9 ff 5e 06 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f RSP: 0018:ffff8801d942eb10 EFLAGS: 00010086 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff81647515 RDI: 0000000000000005 RBP: ffff8801d942eb50 R08: ffff8801d941e580 R09: ffffed003b5c3eda R10: ffffed003b5c3eda R11: ffff8801dae1f6d7 R12: 0000000000000001 R13: ffffffff8939a4e0 R14: 0000000000000000 R15: ffffffff884102c0 __debug_check_no_obj_freed lib/debugobjects.c:786 [inline] debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:818 kmem_cache_free+0x202/0x290 mm/slab.c:3759 free_task_struct kernel/fork.c:163 [inline] free_task+0x16e/0x1f0 kernel/fork.c:457 __put_task_struct+0x2e6/0x620 kernel/fork.c:730 put_task_struct include/linux/sched/task.h:96 [inline] finish_task_switch+0x66b/0x920 kernel/sched/core.c:2715 context_switch kernel/sched/core.c:2834 [inline] __schedule+0x8d7/0x21d0 kernel/sched/core.c:3480 kobject: 'loop5' (00000000ed73ec7b): kobject_uevent_env preempt_schedule_common+0x1f/0xe0 kernel/sched/core.c:3604 kobject: 'loop5' (00000000ed73ec7b): fill_kobj_path: path = '/devices/virtual/block/loop5' preempt_schedule+0x4d/0x60 kernel/sched/core.c:3630 ___preempt_schedule+0x16/0x18 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xbb/0xd0 kernel/locking/spinlock.c:184 spin_unlock_irqrestore include/linux/spinlock.h:384 [inline] pty_write+0x170/0x1f0 drivers/tty/pty.c:126 tty_put_char+0x137/0x160 drivers/tty/tty_io.c:3013 kobject: 'loop0' (000000002d2279cb): kobject_uevent_env __process_echoes+0x462/0x9b0 drivers/tty/n_tty.c:727 kobject: 'loop0' (000000002d2279cb): fill_kobj_path: path = '/devices/virtual/block/loop0' flush_echoes drivers/tty/n_tty.c:827 [inline] __receive_buf drivers/tty/n_tty.c:1646 [inline] n_tty_receive_buf_common+0x11bf/0x2cb0 drivers/tty/n_tty.c:1740 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1775 tty_ldisc_receive_buf+0xb0/0x190 drivers/tty/tty_buffer.c:461 tty_port_default_receive_buf+0x115/0x180 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:481 [inline] flush_to_ldisc+0x3cf/0x5a0 drivers/tty/tty_buffer.c:533 process_one_work+0xc8b/0x1c40 kernel/workqueue.c:2153 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 ====================================================== WARNING: possible circular locking dependency detected 4.19.0-rc7-next-20181015+ #94 Not tainted ------------------------------------------------------ kworker/u4:1/21 is trying to acquire lock: 000000007befcad7 ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 but task is already holding lock: 0000000028068945 (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:777 [inline] 0000000028068945 (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:818 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&obj_hash[i].lock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 __debug_object_init+0x127/0x1290 lib/debugobjects.c:384 debug_object_init+0x16/0x20 lib/debugobjects.c:432 debug_hrtimer_init kernel/time/hrtimer.c:410 [inline] debug_init kernel/time/hrtimer.c:458 [inline] hrtimer_init+0x97/0x490 kernel/time/hrtimer.c:1308 init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057 __sched_fork+0x2ae/0x590 kernel/sched/core.c:2166 init_idle+0x75/0x740 kernel/sched/core.c:5382 sched_init+0xb33/0xc02 kernel/sched/core.c:6065 start_kernel+0x4be/0xa2b init/main.c:608 x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472 x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #2 (&rq->lock){-.-.}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144 rq_lock kernel/sched/sched.h:1127 [inline] task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9768 sched_fork+0x443/0xba0 kernel/sched/core.c:2359 copy_process+0x2585/0x8770 kernel/fork.c:1887 _do_fork+0x1cb/0x11c0 kernel/fork.c:2216 kernel_thread+0x34/0x40 kernel/fork.c:2275 rest_init+0x28/0x372 init/main.c:409 arch_call_rest_init+0xe/0x1b start_kernel+0x9f0/0xa2b init/main.c:745 x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472 x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #1 (&p->pi_lock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 try_to_wake_up+0xd2/0x12e0 kernel/sched/core.c:1965 wake_up_process+0x10/0x20 kernel/sched/core.c:2129 __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262 up+0x13c/0x1c0 kernel/locking/semaphore.c:187 __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236 console_unlock+0x80c/0x1190 kernel/printk/printk.c:2432 vprintk_emit+0x391/0x990 kernel/printk/printk.c:1922 vprintk_default+0x28/0x30 kernel/printk/printk.c:1964 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1997 kobject_uevent_env+0x96/0x101e lib/kobject_uevent.c:467 call_crda net/wireless/reg.c:556 [inline] reg_query_database+0x283/0x400 net/wireless/reg.c:1104 reg_process_hint_core net/wireless/reg.c:2339 [inline] reg_process_hint+0x189/0xec0 net/wireless/reg.c:2677 reg_process_pending_hints net/wireless/reg.c:2767 [inline] reg_todo+0x49a/0xc20 net/wireless/reg.c:2844 process_one_work+0xc8b/0x1c40 kernel/workqueue.c:2153 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 -> #0 ((console_sem).lock){-.-.}: lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3845 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219 console_trylock+0x15/0xa0 kernel/printk/printk.c:2247 console_trylock_spinning kernel/printk/printk.c:1653 [inline] vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921 vprintk_default+0x28/0x30 kernel/printk/printk.c:1964 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1997 __warn_printk+0x8c/0xe0 kernel/panic.c:594 debug_print_object+0x16a/0x210 lib/debugobjects.c:326 __debug_check_no_obj_freed lib/debugobjects.c:786 [inline] debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:818 kmem_cache_free+0x202/0x290 mm/slab.c:3759 free_task_struct kernel/fork.c:163 [inline] free_task+0x16e/0x1f0 kernel/fork.c:457 __put_task_struct+0x2e6/0x620 kernel/fork.c:730 put_task_struct include/linux/sched/task.h:96 [inline] finish_task_switch+0x66b/0x920 kernel/sched/core.c:2715 context_switch kernel/sched/core.c:2834 [inline] __schedule+0x8d7/0x21d0 kernel/sched/core.c:3480 preempt_schedule_common+0x1f/0xe0 kernel/sched/core.c:3604 preempt_schedule+0x4d/0x60 kernel/sched/core.c:3630 ___preempt_schedule+0x16/0x18 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xbb/0xd0 kernel/locking/spinlock.c:184 spin_unlock_irqrestore include/linux/spinlock.h:384 [inline] pty_write+0x170/0x1f0 drivers/tty/pty.c:126 tty_put_char+0x137/0x160 drivers/tty/tty_io.c:3013 __process_echoes+0x462/0x9b0 drivers/tty/n_tty.c:727 flush_echoes drivers/tty/n_tty.c:827 [inline] __receive_buf drivers/tty/n_tty.c:1646 [inline] n_tty_receive_buf_common+0x11bf/0x2cb0 drivers/tty/n_tty.c:1740 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1775 tty_ldisc_receive_buf+0xb0/0x190 drivers/tty/tty_buffer.c:461 tty_port_default_receive_buf+0x115/0x180 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:481 [inline] flush_to_ldisc+0x3cf/0x5a0 drivers/tty/tty_buffer.c:533 process_one_work+0xc8b/0x1c40 kernel/workqueue.c:2153 worker_thread+0x17f/0x1390 kernel/workqueue.c:2296 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 other info that might help us debug this: Chain exists of: (console_sem).lock --> &rq->lock --> &obj_hash[i].lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&obj_hash[i].lock); lock(&rq->lock); lock(&obj_hash[i].lock); lock((console_sem).lock); *** DEADLOCK *** 7 locks held by kworker/u4:1/21: #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: __write_once_size include/linux/compiler.h:206 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:59 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 0000000067c39a5f ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0xb43/0x1c40 kernel/workqueue.c:2124 #1: 00000000604eff48 ((work_completion)(&buf->work)){+.+.}, at: process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128 #2: 00000000401672e5 (&port->buf.lock/1){+.+.}, at: flush_to_ldisc+0xbf/0x5a0 drivers/tty/tty_buffer.c:505 #3: 00000000fdb63fbf (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x22/0x90 drivers/tty/tty_ldisc.c:284 #4: 00000000a9d165c0 (&o_tty->termios_rwsem/1){++++}, at: n_tty_receive_buf_common+0xeb/0x2cb0 drivers/tty/n_tty.c:1703 #5: 00000000c18e16e5 (&ldata->output_lock){+.+.}, at: flush_echoes drivers/tty/n_tty.c:825 [inline] #5: 00000000c18e16e5 (&ldata->output_lock){+.+.}, at: __receive_buf drivers/tty/n_tty.c:1646 [inline] #5: 00000000c18e16e5 (&ldata->output_lock){+.+.}, at: n_tty_receive_buf_common+0x1187/0x2cb0 drivers/tty/n_tty.c:1740 #6: 0000000028068945 (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:777 [inline] #6: 0000000028068945 (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:818 stack backtrace: CPU: 0 PID: 21 Comm: kworker/u4:1 Not tainted 4.19.0-rc7-next-20181015+ #94 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 print_circular_bug.isra.35.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1222 check_prev_add kernel/locking/lockdep.c:1864 [inline] check_prevs_add kernel/locking/lockdep.c:1977 [inline] validate_chain kernel/locking/lockdep.c:2348 [inline] __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3342 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3845 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219 console_trylock+0x15/0xa0 kernel/printk/printk.c:2247 console_trylock_spinning kernel/printk/printk.c:1653 [inline] vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921 vprintk_default+0x28/0x30 kernel/printk/printk.c:1964 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1997 __warn_printk+0x8c/0xe0 kernel/panic.c:594 debug_print_object+0x16a/0x210 lib/debugobjects.c:326 __debug_check_no_obj_freed lib/debugobjects.c:786 [inline] debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:818 kmem_cache_free+0x202/0x290 mm/slab.c:3759 free_task_struct kernel/fork.c:163 [inline] free_task+0x16e/0x1f0 kernel/fork.c:457 __put_task_struct+0x2e6/0x620 kernel/fork.c:730 put_task_struct include/linux/sched/task.h:96 [inline] finish_task_switch+0x66b/0x920 kernel/sched/core.c:2715 context_switch kernel/sched/core.c:2834 [inline] __schedule+0x8d7/0x21d0 kernel/sched/core.c:3480 preempt_schedule_common+0x1f/0xe0 kernel/sched/core.c:3604 preempt_schedule+0x4d/0x60 kernel/sched/core.c:3630 ___preempt_schedule+0x16/0x18 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xbb/0xd0 kernel/locking/spinlock.c:184 spin_unlock_irqrestore include/linux/spinlock.h:384 [inline] pty_write+0x170/0x1f0 drivers/tty/pty.c:126 tty_put_char+0x137/0x160 drivers/tty/tty_io.c:3013 __process_echoes+0x462/0x9b0 drivers/tty/n_tty.c:727 flush_echoes drivers/tty/n_tty.c:827 [inline] __receive_buf drivers/tty/n_tty.c:1646 [inline] n_tty_receive_buf_common+0x11bf/0x2cb0 drivers/tty/n_tty.c:1740 ? lock_is_held_type+0x Lost 50 message(s)! Kernel Offset: disabled Rebooting in 86400 seconds..