Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe

From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Takashi Iwai <tiwai@suse.de>
Cc: Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Oliver Neukum <oneukum@suse.com>,
	Vasily Khoruzhick <anarsoul@gmail.com>,
	alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] sound: line6: Fix race condition in line6_probe
Date: Mon, 17 May 2021 23:48:11 +0900	[thread overview]
Message-ID: <20210517144811.GA54892@hyeyoo> (raw)
In-Reply-To: <s5hk0nxo4qr.wl-tiwai@suse.de>

On Mon, May 17, 2021 at 03:43:24PM +0200, Takashi Iwai wrote:
> The actually needed initialization is
> line6_init_mid() call, and this can be fixed by moving to the
> appropriate place instead of inside each private_init callback.

Oh, I missed it! there was another caller of line6_init_midi.
your fix seems promising to me. it's putting line6_init_midi
to the right place.

by the way looking at code, I think this driver needs some
refactoring... it doesn't handle exceptions well.

Thanks,

Hyeonggon
> ---
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index a030dd65eb28..9602929b7de9 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -699,6 +699,10 @@ static int line6_init_cap_control(struct usb_line6 *line6)
>  		line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
>  		if (!line6->buffer_message)
>  			return -ENOMEM;
> +
> +		ret = line6_init_midi(line6);
> +		if (ret < 0)
> +			return ret;
>  	} else {
>  		ret = line6_hwdep_init(line6);
>  		if (ret < 0)
> diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
> index cd44cb5f1310..16e644330c4d 100644
> --- a/sound/usb/line6/pod.c
> +++ b/sound/usb/line6/pod.c
> @@ -376,11 +376,6 @@ static int pod_init(struct usb_line6 *line6,
>  	if (err < 0)
>  		return err;
>  
> -	/* initialize MIDI subsystem: */
> -	err = line6_init_midi(line6);
> -	if (err < 0)
> -		return err;
> -
>  	/* initialize PCM subsystem: */
>  	err = line6_init_pcm(line6, &pod_pcm_properties);
>  	if (err < 0)
> diff --git a/sound/usb/line6/variax.c b/sound/usb/line6/variax.c
> index ed158f04de80..1376fc405c7f 100644
> --- a/sound/usb/line6/variax.c
> +++ b/sound/usb/line6/variax.c
> @@ -172,11 +172,6 @@ static int variax_init(struct usb_line6 *line6,
>  	if (variax->buffer_activate == NULL)
>  		return -ENOMEM;
>  
> -	/* initialize MIDI subsystem: */
> -	err = line6_init_midi(&variax->line6);
> -	if (err < 0)
> -		return err;
> -
>  	/* initiate startup procedure: */
>  	schedule_delayed_work(&line6->startup_work,
>  			      msecs_to_jiffies(VARIAX_STARTUP_DELAY1));