[PATCH] ASoC: soc-compress: lock pcm_mutex to resolve lockdep error

["Gyeongtaek Lee" <gt82.lee@xxxxxxxxxxx>]

If panic_on_warn=1 is added in bootargs and compress offload playback with
DPCM is started, kernel panic would be occurred because rtd->card->pcm_mutex
isn't held in soc_compr_open_fe() and soc_compr_free_fe() and it generates
lockdep warning in the following code.

void snd_soc_runtime_action(struct snd_soc_pcm_runtime *rtd,
			    int stream, int action)
{
	struct snd_soc_dai *dai;
	int i;

	lockdep_assert_held(&rtd->card->pcm_mutex);

To prevent lockdep warning but minimize side effect by adding mutex,
pcm_mutex is held just before snd_soc_runtime_activate() and
snd_soc_runtime_deactivate() and is released right after them.

Signed-off-by: Gyeongtaek Lee <gt82.lee@xxxxxxxxxxx>
---
 sound/soc/soc-compress.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
index 246a5e32e22a..b4810266f5e5 100644
--- a/sound/soc/soc-compress.c
+++ b/sound/soc/soc-compress.c
@@ -153,7 +153,9 @@ static int soc_compr_open_fe(struct snd_compr_stream *cstream)
 	fe->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
 	fe->dpcm[stream].runtime_update = SND_SOC_DPCM_UPDATE_NO;
 
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
 	snd_soc_runtime_activate(fe, stream);
+	mutex_unlock(&fe->card->pcm_mutex);
 
 	mutex_unlock(&fe->card->mutex);
 
@@ -181,7 +183,9 @@ static int soc_compr_free_fe(struct snd_compr_stream *cstream)
 
 	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
 
+	mutex_lock_nested(&fe->card->pcm_mutex, fe->card->pcm_subclass);
 	snd_soc_runtime_deactivate(fe, stream);
+	mutex_unlock(&fe->card->pcm_mutex);
 
 	fe->dpcm[stream].runtime_update = SND_SOC_DPCM_UPDATE_FE;
 

base-commit: e49d033bddf5b565044e2abe4241353959bc9120
-- 
2.21.0