[alsa-devel] [PATCH] ASoC: soc-core: fixup dead-lock at snd_soc_unregister_component()

[Kuninori Morimoto]

From: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>

snd_soc_unregister_component() is calling snd_soc_lookup_component()
under mutex_lock(). But, snd_soc_lookup_component() itself is using
mutex_lock(), thus it will be dead-lock.
This patch adds _nolocked version of it, and avoid dead-lock issue.

Fixes: ac6a4dd3e9f0("ASoC: soc-core: use snd_soc_lookup_component() at snd_soc_unregister_component()")
Reported-by: "kernelci.org bot" <bot at kernelci.org>"
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>
---
> Please double check/test it.

 sound/soc/soc-core.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index cc59687..94f1078 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -356,14 +356,13 @@ struct snd_soc_component *snd_soc_rtdcom_lookup(struct snd_soc_pcm_runtime *rtd,
 }
 EXPORT_SYMBOL_GPL(snd_soc_rtdcom_lookup);
 
-struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
-						   const char *driver_name)
+static struct snd_soc_component
+*snd_soc_lookup_component_nolocked(struct device *dev, const char *driver_name)
 {
 	struct snd_soc_component *component;
 	struct snd_soc_component *found_component;
 
 	found_component = NULL;
-	mutex_lock(&client_mutex);
 	for_each_component(component) {
 		if ((dev == component->dev) &&
 		    (!driver_name ||
@@ -373,10 +372,21 @@ struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
 			break;
 		}
 	}
-	mutex_unlock(&client_mutex);
 
 	return found_component;
 }
+
+struct snd_soc_component *snd_soc_lookup_component(struct device *dev,
+						   const char *driver_name)
+{
+	struct snd_soc_component *component;
+
+	mutex_lock(&client_mutex);
+	component = snd_soc_lookup_component_nolocked(dev, driver_name);
+	mutex_unlock(&client_mutex);
+
+	return component;
+}
 EXPORT_SYMBOL_GPL(snd_soc_lookup_component);
 
 struct snd_pcm_substream *snd_soc_get_dai_substream(struct snd_soc_card *card,
@@ -2853,7 +2863,7 @@ void snd_soc_unregister_component(struct device *dev)
 
 	mutex_lock(&client_mutex);
 	while (1) {
-		component = snd_soc_lookup_component(dev, NULL);
+		component = snd_soc_lookup_component_nolocked(dev, NULL);
 		if (!component)
 			break;
 
-- 
2.7.4