Message-ID: <20220304104942.lypg3wvlgk2ywi2t@houat>
Date:   Fri, 4 Mar 2022 11:49:42 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Deadlock at reboot?

Hi,

I'm not entirely sure who I'm supposed to send this to, so apologies if
I forgot somebody.

I've had an issue when rebooting on and off for a couple of monthes, but
I got a stacktrace from lockdep today:

[71721.872904] reboot: Restarting system
[71721.876743] ------------[ cut here ]------------
[71721.877081]
[71721.877084] ======================================================
[71721.877086] WARNING: possible circular locking dependency detected
[71721.877088] 5.17.0-rc6-next-20220303-v8+ #10 Not tainted
[71721.877092] ------------------------------------------------------
[71721.877094] swapper/1/0 is trying to acquire lock:
[71721.877097] ffffffc009610900 (console_owner){-.-.}-{0:0}, at: console_unlock+0x194/0x4e0
[71721.877117]
[71721.877117] but task is already holding lock:
[71721.877118] ffffff80fb7974d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x30/0x50
[71721.877131]
[71721.877131] which lock already depends on the new lock.
[71721.877131]
[71721.877132]
[71721.877132] the existing dependency chain (in reverse order) is:
[71721.877133]
[71721.877133] -> #4 (&rq->__lock){-.-.}-{2:2}:
[71721.877139]        __lock_acquire+0x458/0xab0
[71721.877146]        lock_acquire.part.0+0x9c/0x1e0
[71721.877152]        lock_acquire+0x68/0x84
[71721.877157]        _raw_spin_lock_nested+0x6c/0x84
[71721.877164]        raw_spin_rq_lock_nested+0x30/0x50
[71721.877169]        task_fork_fair+0x48/0x164
[71721.877175]        sched_cgroup_fork+0xd4/0x130
[71721.877181]        copy_process+0xd88/0x1380
[71721.877188]        kernel_clone+0x98/0x364
[71721.877193]        kernel_thread+0x78/0xb0
[71721.877198]        rest_init+0x38/0x2c0
[71721.877202]        arch_call_rest_init+0x1c/0x28
[71721.877207]        start_kernel+0x644/0x684
[71721.877211]        __primary_switched+0xa4/0xac
[71721.877214]
[71721.877214] -> #3 (&p->pi_lock){-.-.}-{2:2}:
[71721.877220]        __lock_acquire+0x458/0xab0
[71721.877225]        lock_acquire.part.0+0x9c/0x1e0
[71721.877230]        lock_acquire+0x68/0x84
[71721.877234]        _raw_spin_lock_irqsave+0x90/0xd0
[71721.877241]        try_to_wake_up+0x60/0x460
[71721.877247]        default_wake_function+0x28/0x50
[71721.877253]        woken_wake_function+0x2c/0x40
[71721.877257]        __wake_up_common+0xa0/0x180
[71721.877261]        __wake_up_common_lock+0x80/0xd0
[71721.877265]        __wake_up+0x24/0x30
[71721.877268]        tty_wakeup+0x40/0x80
[71721.877274]        tty_port_default_wakeup+0x2c/0x4c
[71721.877278]        tty_port_tty_wakeup+0x24/0x30
[71721.877282]        uart_write_wakeup+0x24/0x34
[71721.877288]        serial8250_tx_chars+0x110/0x250
[71721.877293]        serial8250_handle_irq.part.0+0x11c/0x170
[71721.877297]        serial8250_default_handle_irq+0x58/0x9c
[71721.877301]        serial8250_interrupt+0x5c/0xc0
[71721.877305]        __handle_irq_event_percpu+0x9c/0x1b4
[71721.877310]        handle_irq_event+0x58/0x130
[71721.877314]        handle_fasteoi_irq+0xb0/0x1f0
[71721.877321]        generic_handle_domain_irq+0x48/0x6c
[71721.877325]        gic_handle_irq+0x88/0xc0
[71721.877329]        call_on_irq_stack+0x2c/0x58
[71721.877334]        do_interrupt_handler+0x88/0xa0
[71721.877339]        el1_interrupt+0x34/0x50
[71721.877342]        el1h_64_irq_handler+0x18/0x24
[71721.877346]        el1h_64_irq+0x64/0x68
[71721.877349]        arch_cpu_idle+0x18/0x2c
[71721.877353]        default_idle_call+0x6c/0x104
[71721.877358]        cpuidle_idle_call+0x158/0x190
[71721.877362]        do_idle+0xdc/0x114
[71721.877365]        cpu_startup_entry+0x34/0xa0
[71721.877369]        rest_init+0x1bc/0x2c0
[71721.877373]        arch_call_rest_init+0x1c/0x28
[71721.877376]        start_kernel+0x644/0x684
[71721.877379]        __primary_switched+0xa4/0xac
[71721.877383]
[71721.877383] -> #2 (&tty->write_wait){-.-.}-{2:2}:
[71721.877389]        __lock_acquire+0x458/0xab0
[71721.877393]        lock_acquire.part.0+0x9c/0x1e0
[71721.877398]        lock_acquire+0x68/0x84
[71721.877403]        _raw_spin_lock_irqsave+0x90/0xd0
[71721.877408]        __wake_up_common_lock+0x60/0xd0
[71721.877412]        __wake_up+0x24/0x30
[71721.877416]        tty_wakeup+0x40/0x80
[71721.877421]        tty_port_default_wakeup+0x2c/0x4c
[71721.877425]        tty_port_tty_wakeup+0x24/0x30
[71721.877428]        uart_write_wakeup+0x24/0x34
[71721.877433]        serial8250_tx_chars+0x110/0x250
[71721.877438]        serial8250_handle_irq.part.0+0x11c/0x170
[71721.877442]        serial8250_default_handle_irq+0x58/0x9c
[71721.877446]        serial8250_interrupt+0x5c/0xc0
[71721.877450]        __handle_irq_event_percpu+0x9c/0x1b4
[71721.877454]        handle_irq_event+0x58/0x130
[71721.877459]        handle_fasteoi_irq+0xb0/0x1f0
[71721.877464]        generic_handle_domain_irq+0x48/0x6c
[71721.877468]        gic_handle_irq+0x88/0xc0
[71721.877472]        call_on_irq_stack+0x2c/0x58
[71721.877476]        do_interrupt_handler+0x88/0xa0
[71721.877481]        el1_interrupt+0x34/0x50
[71721.877484]        el1h_64_irq_handler+0x18/0x24
[71721.877487]        el1h_64_irq+0x64/0x68
[71721.877491]        arch_cpu_idle+0x18/0x2c
[71721.877494]        default_idle_call+0x6c/0x104
[71721.877499]        cpuidle_idle_call+0x158/0x190
[71721.877503]        do_idle+0xdc/0x114
[71721.877507]        cpu_startup_entry+0x34/0xa0
[71721.877510]        rest_init+0x1bc/0x2c0
[71721.877514]        arch_call_rest_init+0x1c/0x28
[71721.877518]        start_kernel+0x644/0x684
[71721.877521]        __primary_switched+0xa4/0xac
[71721.877524]
[71721.877524] -> #1 (&port_lock_key){-.-.}-{2:2}:
[71721.877529]        __lock_acquire+0x458/0xab0
[71721.877534]        lock_acquire.part.0+0x9c/0x1e0
[71721.877539]        lock_acquire+0x68/0x84
[71721.877543]        _raw_spin_lock_irqsave+0x90/0xd0
[71721.877549]        serial8250_console_write+0x1b4/0x3a0
[71721.877554]        univ8250_console_write+0x30/0x40
[71721.877557]        call_console_drivers.constprop.0+0x100/0x1fc
[71721.877561]        console_unlock+0x1ec/0x4e0
[71721.877564]        register_console+0x13c/0x2b0
[71721.877567]        uart_add_one_port+0x33c/0x370
[71721.877573]        serial8250_register_8250_port+0x328/0x420
[71721.877576]        bcm2835aux_serial_probe+0x1c0/0x290
[71721.877585]        platform_probe+0x74/0xf0
[71721.877591]        really_probe.part.0+0xa4/0x300
[71721.877596]        __driver_probe_device+0xa0/0x150
[71721.877600]        driver_probe_device+0xb4/0x150
[71721.877604]        __driver_attach+0x110/0x1b0
[71721.877608]        bus_for_each_dev+0x7c/0xe0
[71721.877612]        driver_attach+0x30/0x3c
[71721.877616]        bus_add_driver+0x15c/0x200
[71721.877620]        driver_register+0x84/0x140
[71721.877624]        __platform_driver_register+0x34/0x40
[71721.877630]        bcm2835aux_serial_driver_init+0x28/0x34
[71721.877634]        do_one_initcall+0x54/0x1a0
[71721.877638]        kernel_init_freeable+0x1dc/0x25c
[71721.877642]        kernel_init+0x30/0x140
[71721.877645]        ret_from_fork+0x10/0x20
[71721.877649]
[71721.877649] -> #0 (console_owner){-.-.}-{0:0}:
[71721.877654]        check_prev_add+0xac/0xbcc
[71721.877659]        validate_chain+0x420/0x5d0
[71721.877664]        __lock_acquire+0x458/0xab0
[71721.877668]        lock_acquire.part.0+0x9c/0x1e0
[71721.877673]        lock_acquire+0x68/0x84
[71721.877678]        console_unlock+0x1dc/0x4e0
[71721.877681]        vprintk_emit+0x1c8/0x1ec
[71721.877684]        vprintk_default+0x44/0x50
[71721.877688]        vprintk+0xc4/0x110
[71721.877691]        _printk+0x68/0x90
[71721.877697]        report_bug+0x104/0x130
[71721.877704]        bug_handler+0x2c/0x80
[71721.877707]        call_break_hook+0x70/0x84
[71721.877711]        brk_handler+0x28/0x70
[71721.877714]        do_debug_exception+0xa4/0x130
[71721.877721]        el1_dbg+0x70/0x8c
[71721.877724]        el1h_64_sync_handler+0x94/0xd0
[71721.877728]        el1h_64_sync+0x64/0x68
[71721.877731]        set_task_cpu+0x1b4/0x1f0
[71721.877736]        detach_tasks+0x148/0x380
[71721.877741]        load_balance+0x240/0x750
[71721.877746]        rebalance_domains+0x3c0/0x4d0
[71721.877751]        _nohz_idle_balance.constprop.0.isra.0+0x1ec/0x380
[71721.877757]        run_rebalance_domains+0x70/0x80
[71721.877762]        __do_softirq+0x1a0/0x37c
[71721.877765]        __irq_exit_rcu+0x120/0x160
[71721.877770]        irq_exit_rcu+0x1c/0x44
[71721.877774]        el1_interrupt+0x38/0x50
[71721.877777]        el1h_64_irq_handler+0x18/0x24
[71721.877780]        el1h_64_irq+0x64/0x68
[71721.877783]        arch_cpu_idle+0x18/0x2c
[71721.877787]        default_idle_call+0x6c/0x104
[71721.877792]        cpuidle_idle_call+0x158/0x190
[71721.877796]        do_idle+0xdc/0x114
[71721.877799]        cpu_startup_entry+0x30/0xa0
[71721.877803]        secondary_start_kernel+0xdc/0x100
[71721.877809]        __secondary_switched+0xa0/0xa4
[71721.877814]
[71721.877814] other info that might help us debug this:
[71721.877814]
[71721.877815] Chain exists of:
[71721.877815]   console_owner --> &p->pi_lock --> &rq->__lock
[71721.877815]
[71721.877821]  Possible unsafe locking scenario:
[71721.877821]
[71721.877823]        CPU0                    CPU1
[71721.877824]        ----                    ----
[71721.877825]   lock(&rq->__lock);
[71721.877827]                                lock(&p->pi_lock);
[71721.877830]                                lock(&rq->__lock);
[71721.877832]   lock(console_owner);
[71721.877835]
[71721.877835]  *** DEADLOCK ***
[71721.877835]
[71721.877836] 3 locks held by swapper/1/0:
[71721.877839]  #0: ffffffc009681fe8 (rcu_read_lock){....}-{1:2}, at: rebalance_domains+0x8c/0x4d0
[71721.877850]  #1: ffffff80fb7974d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x30/0x50
[71721.877861]  #2: ffffffc009610790 (console_lock){+.+.}-{0:0}, at: console_trylock_spinning+0x20/0x1a4
[71721.877870]
[71721.877870] stack backtrace:
[71721.877872] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-next-20220303-v8+ #10
[71721.877877] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[71721.877880] Call trace:
[71721.877881]  dump_backtrace.part.0+0xd4/0xe0
[71721.877884]  show_stack+0x24/0x80
[71721.877888]  dump_stack_lvl+0x8c/0xb8
[71721.877893]  dump_stack+0x18/0x34
[71721.877896]  print_circular_bug+0x1f8/0x200
[71721.877901]  check_noncircular+0x130/0x144
[71721.877906]  check_prev_add+0xac/0xbcc
[71721.877910]  validate_chain+0x420/0x5d0
[71721.877915]  __lock_acquire+0x458/0xab0
[71721.877920]  lock_acquire.part.0+0x9c/0x1e0
[71721.877924]  lock_acquire+0x68/0x84
[71721.877929]  console_unlock+0x1dc/0x4e0
[71721.877932]  vprintk_emit+0x1c8/0x1ec
[71721.877936]  vprintk_default+0x44/0x50
[71721.877939]  vprintk+0xc4/0x110
[71721.877943]  _printk+0x68/0x90
[71721.877948]  report_bug+0x104/0x130
[71721.877953]  bug_handler+0x2c/0x80
[71721.877956]  call_break_hook+0x70/0x84
[71721.877960]  brk_handler+0x28/0x70
[71721.877964]  do_debug_exception+0xa4/0x130
[71721.877970]  el1_dbg+0x70/0x8c
[71721.877973]  el1h_64_sync_handler+0x94/0xd0
[71721.877976]  el1h_64_sync+0x64/0x68
[71721.877980]  set_task_cpu+0x1b4/0x1f0
[71721.877985]  detach_tasks+0x148/0x380
[71721.877990]  load_balance+0x240/0x750
[71721.877995]  rebalance_domains+0x3c0/0x4d0
[71721.878000]  _nohz_idle_balance.constprop.0.isra.0+0x1ec/0x380
[71721.878006]  run_rebalance_domains+0x70/0x80
[71721.878011]  __do_softirq+0x1a0/0x37c
[71721.878014]  __irq_exit_rcu+0x120/0x160
[71721.878018]  irq_exit_rcu+0x1c/0x44
[71721.878022]  el1_interrupt+0x38/0x50
[71721.878026]  el1h_64_irq_handler+0x18/0x24
[71721.878029]  el1h_64_irq+0x64/0x68
[71721.878032]  arch_cpu_idle+0x18/0x2c
[71721.878035]  default_idle_call+0x6c/0x104
[71721.878041]  cpuidle_idle_call+0x158/0x190
[71721.878045]  do_idle+0xdc/0x114
[71721.878048]  cpu_startup_entry+0x30/0xa0
[71721.878052]  secondary_start_kernel+0xdc/0x100
[71721.878057]  __secondary_switched+0xa0/0xa4
[71722.926930] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:3052 set_task_cpu+0x1b4/0x1f0
[71722.935049] Modules linked in:
[71722.938139] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-next-20220303-v8+ #10
[71722.946164] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[71722.950095] SMP: failed to stop secondary CPUs 0-1

The board would then require a power cycle to boot again (the changes
were some registers changes in KMS, nothing that would affect this part
of the code)

I'm not entirely sure how to fix it. Some versions seems to be more
affected than others. next-20220303 seems to trigger it 100% of the
time, some older versions would reboot fine. Like I said, it's been on
and off, so I think the source has been there for some time, whether it
works or not depends probably on subtle timings or something like that.

Maxime

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