[alsa-devel] [PATCH] ASoC: dapm: fix module unload/reload failed issue by reset kcontrol's widget list

[Takashi Iwai]

On Tue, 28 Jul 2015 11:03:39 +0200,
Jie Yang wrote:
> 
> We need reset the related kcontrol's widget list during the
> freeing of a widget, otherwise, the widget list may be outdated
> and reference to it may introduce errors(they usually occurs
> during driver modules unloading/reloading).
> 
> Here adding a func dapm_update_kcontrols_of_freeing_widget and
> call it at dapm_update_kcontrols_of_freeing_widget, to fix those
> issues.
> 
> Signed-off-by: Jie Yang <yang.jie at intel.com>
> ---
>  sound/soc/soc-dapm.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index aa327c9..1ad8144 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -2305,6 +2305,35 @@ static void dapm_free_path(struct snd_soc_dapm_path *path)
>  	kfree(path);
>  }
>  
> +/* update all dapm kcontrols that related to a widget which being freed*/
> +static void dapm_update_kcontrols_of_freeing_widget(struct snd_soc_dapm_widget * w)
> +{
> +	struct dapm_kcontrol_data *data = NULL;
> +	int i, j, n;
> +
> +	if (w && w->kcontrols) {
> +		for (i = 0; i < w->num_kcontrols; i++) {
> +			if (w->kcontrols[i] == NULL)
> +				continue;
> +			data = snd_kcontrol_chip(w->kcontrols[i]);
> +			if (data == NULL)
> +				continue;
> +			for (j = 0, n = 0; j < data->wlist->num_widgets; j++) {
> +				if (data->wlist->widgets[j] == w) {
> +					data->wlist->widgets[j] = NULL;
> +					n++;
> +				}
> +			}
> +
> +			if (n) {
> +				data->wlist->num_widgets -= n;

This looks buggy.  You didn't rearrange widgets[] but just put a hole,
yet decreasing the number.

BTW, how does the reference occur while unloading?  Or better to say:
isn't it the module refcount adjusted while accessing the resources?


thanks,

Takashi