linux-kernel - Re: [PATCH printk v5 1/1] printk: extend console

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Date:   Fri, 6 May 2022 15:04:02 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     John Ogness <john.ogness@...utronix.de>,
        Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH printk v5 1/1] printk: extend console_lock for
 per-console locking

Hi John,

On 06.05.2022 14:41, John Ogness wrote:
> On 2022-05-06, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
>> The Amlogic Meson related issue has been investigated and fixed:
>>
>> https://lore.kernel.org/all/b7c81f02-039e-e877-d7c3-6834728d2117@samsung.com/
>>
>> but I just found that there is one more issue.
>>
>> It appears on QCom-based DragonBoard 410c SBC
>> (arch/arm64/boot/dts/qcom/apq8016-sbc.dts). To see it on today's linux
>> next-20220506, one has to revert
>> 42cd402b8fd4672b692400fe5f9eecd55d2794ac, otherwise lockdep triggers
>> other warning and it is turned off too early:
>>
>> ================================
>> WARNING: inconsistent lock state
>> 5.18.0-rc5-next-20220506+ #11869 Not tainted
>> --------------------------------
>> inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
>> swapper/0/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
>> ffff80000aaa8478 (&port_lock_key){?.+.}-{2:2}, at: msm_uart_irq+0x38/0x750
>> {HARDIRQ-ON-W} state was registered at:
>>     lock_acquire.part.0+0xe0/0x230
>>     lock_acquire+0x68/0x84
>>     _raw_spin_lock+0x5c/0x80
>>     __msm_console_write+0x1ac/0x220
>>     msm_console_write+0x48/0x60
>>     __console_emit_next_record+0x188/0x420
>>     printk_kthread_func+0x3a0/0x3bc
>>     kthread+0x118/0x11c
>>     ret_from_fork+0x10/0x20
>> irq event stamp: 12182
>> hardirqs last  enabled at (12181): [<ffff800008e3d2a8>]
>> cpuidle_enter_state+0xc4/0x30c
>>
>> stack backtrace:
>> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.18.0-rc5-next-20220506+ #11869
>> Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
>> Call trace:
>>    dump_backtrace.part.0+0xd0/0xe0
>>    show_stack+0x18/0x6c
>>    dump_stack_lvl+0x8c/0xb8
>>    dump_stack+0x18/0x34
>>    print_usage_bug.part.0+0x208/0x22c
>>    mark_lock+0x710/0x954
>>    __lock_acquire+0x9fc/0x20cc
>>    lock_acquire.part.0+0xe0/0x230
>>    lock_acquire+0x68/0x84
>>    _raw_spin_lock_irqsave+0x80/0xcc
>>    msm_uart_irq+0x38/0x750
>>    __handle_irq_event_percpu+0xac/0x3d0
>>    handle_irq_event+0x4c/0x120
>>    handle_fasteoi_irq+0xa4/0x1a0
>>    generic_handle_domain_irq+0x3c/0x60
>>    gic_handle_irq+0x44/0xc4
>>    call_on_irq_stack+0x2c/0x54
>>    do_interrupt_handler+0x80/0x84
>>    el1_interrupt+0x34/0x64
>>    el1h_64_irq_handler+0x18/0x24
>>    el1h_64_irq+0x64/0x68
>>    cpuidle_enter_state+0xcc/0x30c
>>    cpuidle_enter+0x38/0x50
>>    do_idle+0x22c/0x2bc
>>    cpu_startup_entry+0x28/0x30
>>    rest_init+0x110/0x190
>>    arch_post_acpi_subsys_init+0x0/0x18
>>    start_kernel+0x6c4/0x704
>>    __primary_switched+0xc0/0xc8
>>    INIT: version 2.88 booting
>> [info] Using makefile-style concurrent boot in runlevel S.
> The console write() callback for the msm driver (__msm_console_write)
> assumes interrupts are off and is doing a spin_lock(&port->lock) rather
> than spin_lock_irqsave(&port->lock, flags).
>
> The following change should address the issue:

Right, this help. spin_trylock() should be also converted imho, see below.

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

> John
>
> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
> index 23c94b927776..ab3f360bd354 100644
> --- a/drivers/tty/serial/msm_serial.c
> +++ b/drivers/tty/serial/msm_serial.c
> @@ -1599,6 +1599,7 @@ static inline struct uart_port *msm_get_port_from_line(unsigned int line)
>   static void __msm_console_write(struct uart_port *port, const char *s,
>   				unsigned int count, bool is_uartdm)
>   {
> +	unsigned long flags;
>   	int i;
>   	int num_newlines = 0;
>   	bool replaced = false;
> @@ -1621,7 +1622,7 @@ static void __msm_console_write(struct uart_port *port, const char *s,
>   	else if (oops_in_progress)
>   		locked = spin_trylock(&port->lock);

locked = spin_trylock_irqsave(&port->lock, flags);

>   	else
> -		spin_lock(&port->lock);
> +		spin_lock_irqsave(&port->lock, flags);
>   
>   	if (is_uartdm)
>   		msm_reset_dm_count(port, count);
> @@ -1660,7 +1661,7 @@ static void __msm_console_write(struct uart_port *port, const char *s,
>   	}
>   
>   	if (locked)
> -		spin_unlock(&port->lock);
> +		spin_unlock_irqrestore(&port->lock, flags);
>   }
>   
>   static void msm_console_write(struct console *co, const char *s,

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland