linux-kernel - Re: [Patch v8 4/6] leds: ledtrig-tty: replace mutex with completion

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Message-ID: <2023112310-salaried-shower-bc76@gregkh>
Date:   Thu, 23 Nov 2023 14:10:44 +0000
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Florian Eckert <fe@....tdt.de>
Cc:     Eckert.Florian@...glemail.com, jirislaby@...nel.org, pavel@....cz,
        lee@...nel.org, kabel@...nel.org, u.kleine-koenig@...gutronix.de,
        m.brock@...mierlo.com, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [Patch v8 4/6] leds: ledtrig-tty: replace mutex with completion

On Thu, Nov 09, 2023 at 09:50:36AM +0100, Florian Eckert wrote:
> With this commit, the mutex handling is replaced by the completion
> handling. When handling mutex, it must always be ensured that the held
> mutex is also released again. This is more error-prone should the number
> of code paths increase.
> 
> This is a preparatory commit to make the trigger more configurable via
> additional sysfs parameters. With this change, the worker always runs and
> is no longer stopped if no ttyname is set.
> 
> Signed-off-by: Florian Eckert <fe@....tdt.de>
> ---
>  drivers/leds/trigger/ledtrig-tty.c | 60 +++++++++++++++---------------
>  1 file changed, 31 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
> index 86595add72cd..3badf74fa420 100644
> --- a/drivers/leds/trigger/ledtrig-tty.c
> +++ b/drivers/leds/trigger/ledtrig-tty.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  
> +#include <linux/completion.h>
>  #include <linux/delay.h>
>  #include <linux/leds.h>
>  #include <linux/module.h>
> @@ -12,15 +13,24 @@
>  struct ledtrig_tty_data {
>  	struct led_classdev *led_cdev;
>  	struct delayed_work dwork;
> -	struct mutex mutex;
> +	struct completion sysfs;
>  	const char *ttyname;
>  	struct tty_struct *tty;
>  	int rx, tx;
>  };
>  
> -static void ledtrig_tty_restart(struct ledtrig_tty_data *trigger_data)
> +static int ledtrig_tty_waitforcompletion(struct device *dev)

Nit, you might want to add a few more '_' characters, right:
	ledtrig_tty_wait_for_completion()
to match up with the call to wait_for_completion_timeout() it makes.

>  {
> -	schedule_delayed_work(&trigger_data->dwork, 0);
> +	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
> +	int ret;
> +
> +	ret = wait_for_completion_timeout(&trigger_data->sysfs,
> +					  msecs_to_jiffies(LEDTRIG_TTY_INTERVAL * 20));
> +

Nit, no blank line needed here, if you happen to redo this patch.

thanks,

greg "naming is hard" k-h