BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 271s!
BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=-20 stuck for 261s!
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=10/256
    in-flight: 19:iterate_cleanup_work
    pending: iterate_cleanup_work, defense_work_handler, defense_work_handler, defense_work_handler, defense_work_handler, defense_work_handler, cache_reap, kernfs_notify_workfn, vmpressure_work_fn

======================================================
WARNING: possible circular locking dependency detected
4.19.86-syzkaller #0 Not tainted
------------------------------------------------------
swapper/0/0 is trying to acquire lock:
00000000013d67db (console_owner){-.-.}, at: log_next kernel/printk/printk.c:499 [inline]
00000000013d67db (console_owner){-.-.}, at: console_unlock+0x432/0x10d0 kernel/printk/printk.c:2412

but task is already holding lock:
00000000aa4ee8f8 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold+0x879/0x11dc kernel/workqueue.c:4560

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/0x10a0 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+0x171/0x1c0 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+0x5c8/0x6b0 kernel/workqueue.c:4220
       do_floppy_init drivers/block/floppy.c:4734 [inline]
       floppy_async_init+0x2026/0x2165 drivers/block/floppy.c:4751
       async_run_entry_fn+0x124/0x570 kernel/async.c:127
       process_one_work+0x989/0x1750 kernel/workqueue.c:2153
       worker_thread+0x98/0xe40 kernel/workqueue.c:2296
       kthread+0x354/0x420 kernel/kthread.c:246
       ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

-> #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/0x10a0 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+0xafa/0x10f0 drivers/tty/n_tty.c:2354
       do_tty_write drivers/tty/tty_io.c:960 [inline]
       tty_write+0x458/0x7a0 drivers/tty/tty_io.c:1044
       __vfs_write+0x114/0x810 fs/read_write.c:485
       vfs_write+0x20c/0x560 fs/read_write.c:549
       ksys_write+0x14f/0x2d0 fs/read_write.c:599
       __do_sys_write fs/read_write.c:611 [inline]
       __se_sys_write fs/read_write.c:608 [inline]
       __x64_sys_write+0x73/0xb0 fs/read_write.c:608
       do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
       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+0x57/0x70 drivers/tty/tty_port.c:390
       uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:103
       serial8250_tx_chars+0x495/0xaf0 drivers/tty/serial/8250/8250_port.c:1806
       serial8250_handle_irq.part.0+0x261/0x2b0 drivers/tty/serial/8250/8250_port.c:1879
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1865 [inline]
       serial8250_default_handle_irq+0xc0/0x150 drivers/tty/serial/8250/8250_port.c:1895
       serial8250_interrupt+0xfc/0x1e0 drivers/tty/serial/8250/8250_core.c:125
       __handle_irq_event_percpu+0x144/0x8f0 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+0x25e/0x8d0 kernel/irq/chip.c:797
       generic_handle_irq_desc include/linux/irqdesc.h:155 [inline]
       handle_irq+0x39/0x50 arch/x86/kernel/irq_64.c:87
       do_IRQ+0x99/0x1d0 arch/x86/kernel/irq.c:246
       ret_from_intr+0x0/0x1e
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:556
       default_idle_call+0x36/0x90 kernel/sched/idle.c:93
       cpuidle_idle_call kernel/sched/idle.c:153 [inline]
       do_idle+0x30c/0x4d0 kernel/sched/idle.c:263
       cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:369
       rest_init+0x219/0x222 init/main.c:442
       start_kernel+0x88c/0x8c5 init/main.c:738
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
       x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #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+0x7ca/0x9f0 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:1736 [inline]
       console_unlock+0xbdf/0x10d0 kernel/printk/printk.c:2425
       vprintk_emit+0x238/0x690 kernel/printk/printk.c:1934
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1975
       vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
       printk+0xba/0xed kernel/printk/printk.c:2008
       register_console+0x77f/0xb90 kernel/printk/printk.c:2741
       univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:685
       console_init+0x4f7/0x761 kernel/printk/printk.c:2827
       start_kernel+0x59c/0x8c5 init/main.c:661
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
       x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
       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:1599 [inline]
       console_unlock+0x49c/0x10d0 kernel/printk/printk.c:2422
       vprintk_emit+0x238/0x690 kernel/printk/printk.c:1934
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1975
       vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
       printk+0xba/0xed kernel/printk/printk.c:2008
       show_pwq kernel/workqueue.c:4467 [inline]
       show_workqueue_state.cold+0x9e4/0x11dc kernel/workqueue.c:4562
       wq_watchdog_timer_fn+0x516/0x5a0 kernel/workqueue.c:5574
       call_timer_fn+0x18d/0x720 kernel/time/timer.c:1326
       expire_timers kernel/time/timer.c:1363 [inline]
       __run_timers kernel/time/timer.c:1684 [inline]
       __run_timers kernel/time/timer.c:1652 [inline]
       run_timer_softirq+0xd00/0x16a0 kernel/time/timer.c:1699
       __do_softirq+0x25c/0x921 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+0x13b/0x550 arch/x86/kernel/apic/apic.c:1094
       apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:556
       default_idle_call+0x36/0x90 kernel/sched/idle.c:93
       cpuidle_idle_call kernel/sched/idle.c:153 [inline]
       do_idle+0x30c/0x4d0 kernel/sched/idle.c:263
       cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:369
       rest_init+0x219/0x222 init/main.c:442
       start_kernel+0x88c/0x8c5 init/main.c:738
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
       x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
       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: 00000000b613e180 ((&wq_watchdog_timer)){+.-.}, at: lockdep_copy_map include/linux/lockdep.h:168 [inline]
 #0: 00000000b613e180 ((&wq_watchdog_timer)){+.-.}, at: call_timer_fn+0xda/0x720 kernel/time/timer.c:1316
 #1: 000000008e2ff851 (rcu_read_lock_sched){....}, at: show_workqueue_state+0x0/0x120 kernel/workqueue.c:4432
 #2: 00000000aa4ee8f8 (&(&pool->lock)->rlock){-.-.}, at: show_workqueue_state.cold+0x879/0x11dc kernel/workqueue.c:4560
 #3: 00000000ea44fd73 (console_lock){+.+.}, at: console_trylock_spinning kernel/printk/printk.c:1661 [inline]
 #3: 00000000ea44fd73 (console_lock){+.+.}, at: vprintk_emit+0x21d/0x690 kernel/printk/printk.c:1933

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.86-syzkaller #0
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+0x197/0x210 lib/dump_stack.c:118
 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+0x2e19/0x49c0 kernel/locking/lockdep.c:3411
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3903
 console_lock_spinning_enable kernel/printk/printk.c:1599 [inline]
 console_unlock+0x49c/0x10d0 kernel/printk/printk.c:2422
 vprintk_emit+0x238/0x690 kernel/printk/printk.c:1934
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1975
 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
 printk+0xba/0xed kernel/printk/printk.c:2008
 show_pwq kernel/workqueue.c:4467 [inline]
 show_workqueue_state.cold+0x9e4/0x11dc kernel/workqueue.c:4562
 wq_watchdog_timer_fn+0x516/0x5a0 kernel/workqueue.c:5574
 call_timer_fn+0x18d/0x720 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers kernel/time/timer.c:1684 [inline]
 __run_timers kernel/time/timer.c:1652 [inline]
 run_timer_softirq+0xd00/0x16a0 kernel/time/timer.c:1699
 __do_softirq+0x25c/0x921 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+0x13b/0x550 arch/x86/kernel/apic/apic.c:1094
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
 </IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: ff ff 48 89 df e8 22 4d af fa eb 82 e9 07 00 00 00 0f 00 2d 54 7d 55 00 f4 c3 66 90 e9 07 00 00 00 0f 00 2d 44 7d 55 00 fb f4 <c3> 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 e8 9e 28 67 fa e8 c9
RSP: 0018:ffffffff88607cb0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff10e4b74 RBX: ffffffff88679ec0 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffffffff8867a73c
RBP: ffffffff88607ce0 R08: ffffffff88679ec0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff88725b90 R14: 0000000000000000 R15: ffffffff88679ec0
 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:556
 default_idle_call+0x36/0x90 kernel/sched/idle.c:93
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x30c/0x4d0 kernel/sched/idle.c:263
 cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:369
 rest_init+0x219/0x222 init/main.c:442
 start_kernel+0x88c/0x8c5 init/main.c:738
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
  pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=3/256
    in-flight: 14:linkwatch_event, 7534:switchdev_deferred_process_work switchdev_deferred_process_work
workqueue events_highpri: flags=0x10
  pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256
    pending: flush_backlog BAR(13737)
workqueue events_power_efficient: flags=0x80
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=4/256
    pending: gc_worker, device_uncache_fw_images_work, do_cache_clean, neigh_periodic_work
workqueue mm_percpu_wq: flags=0x8
  pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
    pending: vmstat_update, lru_add_drain_per_cpu BAR(13825)
workqueue kblockd: flags=0x18
  pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256
    pending: blk_mq_timeout_work
workqueue bat_events: flags=0xe000a
  pwq 4: cpus=0-1 flags=0x4 nice=0 active=1/1
    pending: batadv_nc_worker
    delayed: batadv_nc_worker
pool 0: cpus=0 node=0 flags=0x0 nice=0 hung=1s workers=4 idle: 2729 7537
pool 2: cpus=1 node=0 flags=0x0 nice=0 hung=272s workers=5 idle: 3209 7535 7528 24