BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 144s!
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=16/256
    in-flight: 7910:rtc_timer_do_work
    pending: cache_reap, defense_work_handler, defense_work_handler, defense_work_handler, defense_work_handler, rht_deferred_worker, destroy_super_work, nfc_urelease_event_work, kernfs_notify_workfn, nfc_urelease_event_work, nfc_urelease_event_work, nfc_urelease_event_work, destroy_super_work, xfrm_state_gc_task, nfc_urelease_event_work

======================================================
WARNING: possible circular locking dependency detected
4.19.36 #4 Not tainted
------------------------------------------------------
swapper/0/0 is trying to acquire lock:
0000000087c7c7d5 (console_owner){-.-.}, at: log_next kernel/printk/printk.c:497 [inline]
0000000087c7c7d5 (console_owner){-.-.}, at: console_unlock+0x41f/0x10c0 kernel/printk/printk.c:2397

but task is already holding lock:
000000008356a144 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold+0x879/0x11dc kernel/workqueue.c:4557

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&(&pool->lock)->rlock){-.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
       spin_lock include/linux/spinlock.h:329 [inline]
       __queue_work+0x23d/0x10e0 kernel/workqueue.c:1417
       queue_work_on+0x192/0x200 kernel/workqueue.c:1486
       queue_work include/linux/workqueue.h:512 [inline]
       schedule_work include/linux/workqueue.h:570 [inline]
       put_pwq kernel/workqueue.c:1090 [inline]
       put_pwq+0x178/0x1d0 kernel/workqueue.c:1075
       put_pwq_unlocked.part.0+0x34/0x70 kernel/workqueue.c:1107
       put_pwq_unlocked kernel/workqueue.c:1101 [inline]
       destroy_workqueue+0x617/0x6f0 kernel/workqueue.c:4217
       do_floppy_init drivers/block/floppy.c:4704 [inline]
       floppy_async_init+0x202c/0x216b drivers/block/floppy.c:4721
       async_run_entry_fn+0x126/0x570 kernel/async.c:127
       process_one_work+0x98e/0x1760 kernel/workqueue.c:2153
       worker_thread+0x98/0xe40 kernel/workqueue.c:2296
       kthread+0x357/0x430 kernel/kthread.c:246
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413

-> #3 (&pool->lock/1){..-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
       spin_lock include/linux/spinlock.h:329 [inline]
       __queue_work+0x23d/0x10e0 kernel/workqueue.c:1417
       queue_work_on+0x192/0x200 kernel/workqueue.c:1486
       queue_work include/linux/workqueue.h:512 [inline]
       tty_schedule_flip drivers/tty/tty_buffer.c:408 [inline]
       tty_flip_buffer_push+0xc5/0x100 drivers/tty/tty_buffer.c:551
       pty_write+0x1a6/0x200 drivers/tty/pty.c:124
       n_tty_write+0xb06/0x1100 drivers/tty/n_tty.c:2354
       do_tty_write drivers/tty/tty_io.c:960 [inline]
       tty_write+0x45b/0x7a0 drivers/tty/tty_io.c:1044
       __vfs_write+0x116/0x820 fs/read_write.c:485
       vfs_write+0x20c/0x560 fs/read_write.c:549
       ksys_write+0xea/0x1f0 fs/read_write.c:598
       __do_sys_write fs/read_write.c:610 [inline]
       __se_sys_write fs/read_write.c:607 [inline]
       __x64_sys_write+0x73/0xb0 fs/read_write.c:607
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&(&port->lock)->rlock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
       tty_port_tty_get+0x22/0x80 drivers/tty/tty_port.c:288
       tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47
       tty_port_tty_wakeup+0x5d/0x70 drivers/tty/tty_port.c:390
       uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:103
       serial8250_tx_chars+0x4a4/0xb20 drivers/tty/serial/8250/8250_port.c:1806
       serial8250_handle_irq.part.0+0x1e2/0x270 drivers/tty/serial/8250/8250_port.c:1879
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1865 [inline]
       serial8250_default_handle_irq+0xc5/0x150 drivers/tty/serial/8250/8250_port.c:1895
       serial8250_interrupt+0x102/0x1e0 drivers/tty/serial/8250/8250_core.c:125
       __handle_irq_event_percpu+0x146/0x900 kernel/irq/handle.c:149
       handle_irq_event_percpu+0x74/0x160 kernel/irq/handle.c:189
       handle_irq_event+0xa7/0x134 kernel/irq/handle.c:206
       handle_edge_irq+0x264/0x8e0 kernel/irq/chip.c:791
       generic_handle_irq_desc include/linux/irqdesc.h:155 [inline]
       handle_irq+0x252/0x3d8 arch/x86/kernel/irq_64.c:78
       do_IRQ+0x99/0x1d0 arch/x86/kernel/irq.c:246
       ret_from_intr+0x0/0x1e
       arch_local_irq_restore arch/x86/include/asm/paravirt.h:788 [inline]
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
       _raw_spin_unlock_irqrestore+0x95/0xe0 kernel/locking/spinlock.c:184
       spin_unlock_irqrestore include/linux/spinlock.h:384 [inline]
       uart_write+0x3a9/0x6f0 drivers/tty/serial/serial_core.c:615
       process_output_block drivers/tty/n_tty.c:593 [inline]
       n_tty_write+0x3ff/0x1100 drivers/tty/n_tty.c:2331
       do_tty_write drivers/tty/tty_io.c:960 [inline]
       tty_write+0x45b/0x7a0 drivers/tty/tty_io.c:1044
       redirected_tty_write+0xb2/0xc0 drivers/tty/tty_io.c:1065
       __vfs_write+0x116/0x820 fs/read_write.c:485
       vfs_write+0x20c/0x560 fs/read_write.c:549
       ksys_write+0xea/0x1f0 fs/read_write.c:598
       __do_sys_write fs/read_write.c:610 [inline]
       __se_sys_write fs/read_write.c:607 [inline]
       __x64_sys_write+0x73/0xb0 fs/read_write.c:607
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&port_lock_key){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
       serial8250_console_write+0x7ed/0xa10 drivers/tty/serial/8250/8250_port.c:3247
       univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:590
       call_console_drivers kernel/printk/printk.c:1729 [inline]
       console_unlock+0xbe4/0x10c0 kernel/printk/printk.c:2410
       vprintk_emit+0x238/0x690 kernel/printk/printk.c:1927
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1968
       vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
       printk+0xba/0xed kernel/printk/printk.c:2001
       register_console+0x787/0xb90 kernel/printk/printk.c:2725
       univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:685
       console_init+0x4f7/0x761 kernel/printk/printk.c:2811
       start_kernel+0x59f/0x8c8 init/main.c:661
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #0 (console_owner){-.-.}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
       console_lock_spinning_enable kernel/printk/printk.c:1592 [inline]
       console_unlock+0x489/0x10c0 kernel/printk/printk.c:2407
       vprintk_emit+0x238/0x690 kernel/printk/printk.c:1927
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1968
       vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
       printk+0xba/0xed kernel/printk/printk.c:2001
       show_pwq kernel/workqueue.c:4464 [inline]
       show_workqueue_state.cold+0x9e4/0x11dc kernel/workqueue.c:4559
       wq_watchdog_timer_fn+0x516/0x5a0 kernel/workqueue.c:5571
       call_timer_fn+0x190/0x720 kernel/time/timer.c:1326
       expire_timers kernel/time/timer.c:1363 [inline]
       __run_timers kernel/time/timer.c:1682 [inline]
       __run_timers kernel/time/timer.c:1650 [inline]
       run_timer_softirq+0xd03/0x1700 kernel/time/timer.c:1697
       __do_softirq+0x266/0x92f kernel/softirq.c:292
       invoke_softirq kernel/softirq.c:372 [inline]
       irq_exit+0x180/0x1d0 kernel/softirq.c:412
       exiting_irq arch/x86/include/asm/apic.h:536 [inline]
       smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1056
       apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
       native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:57
       arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:552
       default_idle_call+0x36/0x90 kernel/sched/idle.c:93
       cpuidle_idle_call kernel/sched/idle.c:153 [inline]
       do_idle+0x377/0x560 kernel/sched/idle.c:262
       cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:368
       rest_init+0xf1/0xf6 init/main.c:442
       start_kernel+0x88f/0x8c8 init/main.c:738
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

other info that might help us debug this:

Chain exists of:
  console_owner --> &pool->lock/1 --> &(&pool->lock)->rlock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&(&pool->lock)->rlock);
                               lock(&pool->lock/1);
                               lock(&(&pool->lock)->rlock);
  lock(console_owner);

 *** DEADLOCK ***

4 locks held by swapper/0/0:
 #0: 00000000a03b3148 ((&wq_watchdog_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline]
 #0: 00000000a03b3148 ((&wq_watchdog_timer)){+.-.}, at: call_timer_fn+0xda/0x720 kernel/time/timer.c:1316
 #1: 0000000082662955 (rcu_read_lock_sched){....}, at: show_workqueue_state+0x0/0x120 kernel/workqueue.c:4429
 #2: 000000008356a144 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold+0x879/0x11dc kernel/workqueue.c:4557
 #3: 00000000bec2410a (console_lock){+.+.}, at: console_trylock_spinning kernel/printk/printk.c:1654 [inline]
 #3: 00000000bec2410a (console_lock){+.+.}, at: vprintk_emit+0x21d/0x690 kernel/printk/printk.c:1926

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.36 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1861 [inline]
 check_prevs_add kernel/locking/lockdep.c:1974 [inline]
 validate_chain kernel/locking/lockdep.c:2415 [inline]
 __lock_acquire+0x2e6d/0x48f0 kernel/locking/lockdep.c:3411
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
 console_lock_spinning_enable kernel/printk/printk.c:1592 [inline]
 console_unlock+0x489/0x10c0 kernel/printk/printk.c:2407
 vprintk_emit+0x238/0x690 kernel/printk/printk.c:1927
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1968
 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
 printk+0xba/0xed kernel/printk/printk.c:2001
 show_pwq kernel/workqueue.c:4464 [inline]
 show_workqueue_state.cold+0x9e4/0x11dc kernel/workqueue.c:4559
 wq_watchdog_timer_fn+0x516/0x5a0 kernel/workqueue.c:5571
 call_timer_fn+0x190/0x720 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers kernel/time/timer.c:1682 [inline]
 __run_timers kernel/time/timer.c:1650 [inline]
 run_timer_softirq+0xd03/0x1700 kernel/time/timer.c:1697
 __do_softirq+0x266/0x92f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:372 [inline]
 irq_exit+0x180/0x1d0 kernel/softirq.c:412
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1056
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
 </IRQ>
RIP: 0010:native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:58
Code: ff ff ff 48 89 c7 48 89 45 d8 e8 89 f3 b2 fa 48 8b 45 d8 e9 ce fe ff ff 48 89 df e8 78 f3 b2 fa eb 82 90 90 90 90 90 90 fb f4 <c3> 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 90 90 90 90 90 90
RSP: 0018:ffffffff88607ca8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff10e4664 RBX: ffffffff88679e80 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffffffff8867a6fc
RBP: ffffffff88607cd8 R08: ffffffff88679e80 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff88723310 R14: 0000000000000000 R15: 0000000000000000
 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:552
 default_idle_call+0x36/0x90 kernel/sched/idle.c:93
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x377/0x560 kernel/sched/idle.c:262
 cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:368
 rest_init+0xf1/0xf6 init/main.c:442
 start_kernel+0x88f/0x8c8 init/main.c:738
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
workqueue events_long: flags=0x0
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
    pending: br_fdb_cleanup, br_fdb_cleanup
workqueue events_unbound: flags=0x2
  pwq 4: cpus=0-1 flags=0x4 nice=0 active=4/512
    in-flight: 12012:fsnotify_mark_destroy_workfn fsnotify_mark_destroy_workfn, 2752:fsnotify_connector_destroy_workfn fsnotify_connector_destroy_workfn
workqueue events_power_efficient: flags=0x80
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
    pending: check_lifetime, do_cache_clean
workqueue rcu_gp: flags=0x8
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=3/256
    pending: srcu_invoke_callbacks, process_srcu, wait_rcu_exp_gp
workqueue mm_percpu_wq: flags=0x8
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
    pending: vmstat_update
workqueue ipv6_addrconf: flags=0x40008
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1
    pending: addrconf_verify_work
workqueue krxrpcd: flags=0x0
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/1
    pending: rxrpc_peer_keepalive_worker
    delayed: rxrpc_peer_keepalive_worker, rxrpc_peer_keepalive_worker
workqueue bat_events: flags=0xe000a
  pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/1
    pending: batadv_dat_purge
    delayed: batadv_bla_periodic_work, batadv_purge_orig, batadv_purge_orig, batadv_nc_worker, batadv_nc_worker, batadv_nc_worker, batadv_nc_worker, batadv_nc_worker
pool 2: cpus=1 node=0 flags=0x0 nice=0 hung=145s workers=5 idle: 9823 19 25349 10456
pool 4: cpus=0-1 flags=0x4 nice=0 hung=1s workers=9 idle: 26 6988 9545 2299 18941 8052 6991