linux-kernel - Re: [PATCH] Input: pxrc - simplify mutex handling with guard macro

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Message-ID: <ZWnfsjIukIbAvQ-l@hovoldconsulting.com>
Date:   Fri, 1 Dec 2023 14:29:22 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: pxrc - simplify mutex handling with guard macro

On Fri, Dec 01, 2023 at 01:08:45PM +0100, Marcus Folkesson wrote:
> Use the guard(mutex) macro for handle mutex lock/unlocks.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>

A couple of drive-by comments below.

> ---
>  drivers/input/joystick/pxrc.c | 27 +++++++++++----------------
>  1 file changed, 11 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
> index ea2bf5951d67..3c3bf7179b46 100644
> --- a/drivers/input/joystick/pxrc.c
> +++ b/drivers/input/joystick/pxrc.c
> @@ -5,15 +5,17 @@
>   * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@...il.com>
>   */
>  
> -#include <linux/kernel.h>
> +#include <linux/cleanup.h>
>  #include <linux/errno.h>
> -#include <linux/slab.h>
> +#include <linux/input.h>
> +#include <linux/kernel.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
>  #include <linux/uaccess.h>
> +
>  #include <linux/usb.h>
>  #include <linux/usb/input.h>
> -#include <linux/mutex.h>
> -#include <linux/input.h>

Looks like an unrelated change.
  
>  #define PXRC_VENDOR_ID		0x1781
>  #define PXRC_PRODUCT_ID		0x0898
> @@ -89,25 +91,20 @@ static int pxrc_open(struct input_dev *input)
>  		dev_err(&pxrc->intf->dev,
>  			"%s - usb_submit_urb failed, error: %d\n",
>  			__func__, retval);
> -		retval = -EIO;
> -		goto out;
> +		return -EIO;
>  	}
>  
>  	pxrc->is_open = true;
> -
> -out:
> -	mutex_unlock(&pxrc->pm_mutex);
> -	return retval;
> +	return 0;
>  }

Eh, this looks obviously broken. Did you not test this before
submitting? I assume lockdep would complain loudly too.

You're apparently the author of this driver and can test it, but I fear
the coming onslaught of untested guard conversions from the "cleanup"
crew. Not sure I find the result generally more readable either.

Johan