Re: [PATCH v3 1/1] tty: serial: samsung: add spin_lock for interrupt and console_write

From: Jiri Slaby <jirislaby@kernel.org>
To: Jaewon Kim <jaewon02.kim@samsung.com>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alim Akhtar <alim.akhtar@samsung.com>,
	linux-samsung-soc@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org,
	linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
	Chanho Park <chanho61.park@samsung.com>
Subject: Re: [PATCH v3 1/1] tty: serial: samsung: add spin_lock for interrupt and console_write
Date: Thu, 7 Apr 2022 09:46:46 +0200	[thread overview]
Message-ID: <b53be23f-7935-dae3-9dc8-f850493a5fa9@kernel.org> (raw)
In-Reply-To: <20220407071619.102249-2-jaewon02.kim@samsung.com>

On 07. 04. 22, 9:16, Jaewon Kim wrote:
> The console_write and IRQ handler can run concurrently.
> Problems may occurs console_write is continuously executed while
> the IRQ handler is running.

 From the patch POV:

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>

But given this is a v3 with no version changelog below "---", you've 
just kicked the Greg's bot to wake up :P.

> Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
> ---
>   drivers/tty/serial/samsung_tty.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index e1585fbae909..8af5aceb9f4e 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -2480,12 +2480,24 @@ s3c24xx_serial_console_write(struct console *co, const char *s,
>   			     unsigned int count)
>   {
>   	unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
> +	unsigned long flags;
> +	bool locked = true;
>   
>   	/* not possible to xmit on unconfigured port */
>   	if (!s3c24xx_port_configured(ucon))
>   		return;
>   
> +	if (cons_uart->sysrq)
> +		locked = false;
> +	else if (oops_in_progress)
> +		locked = spin_trylock_irqsave(&cons_uart->lock, flags);
> +	else
> +		spin_lock_irqsave(&cons_uart->lock, flags);
> +
>   	uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
> +
> +	if (locked)
> +		spin_unlock_irqrestore(&cons_uart->lock, flags);
>   }
>   
>   /* Shouldn't be __init, as it can be instantiated from other module */

-- 
js
suse labs