[RFC PATCH v2 1/5] ASoC: soc-pcm: remove snd_soc_dpcm_fe_can_update()

[RFC PATCH v2 1/5] ASoC: soc-pcm: remove snd_soc_dpcm_fe_can_update()

[Pierre-Louis Bossart]

This function is not used anywhere, including soc-pcm.c

Remove dead code.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 include/sound/soc-dpcm.h | 3 ---
 sound/soc/soc-pcm.c      | 9 ---------
 2 files changed, 12 deletions(-)

diff --git a/include/sound/soc-dpcm.h b/include/sound/soc-dpcm.h
index bc7af90099a8..72d45ad47ee3 100644
--- a/include/sound/soc-dpcm.h
+++ b/include/sound/soc-dpcm.h
@@ -121,9 +121,6 @@ int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
 int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream);
 
-/* is the current PCM operation for this FE ? */
-int snd_soc_dpcm_fe_can_update(struct snd_soc_pcm_runtime *fe, int stream);
-
 /* is the current PCM operation for this BE ? */
 int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream);
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index fc1854e3e43f..17476e3219ea 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -2805,15 +2805,6 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
 	return ret;
 }
 
-/* is the current PCM operation for this FE ? */
-int snd_soc_dpcm_fe_can_update(struct snd_soc_pcm_runtime *fe, int stream)
-{
-	if (fe->dpcm[stream].runtime_update == SND_SOC_DPCM_UPDATE_FE)
-		return 1;
-	return 0;
-}
-EXPORT_SYMBOL_GPL(snd_soc_dpcm_fe_can_update);
-
 /* is the current PCM operation for this BE ? */
 int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
-- 
2.25.1

[RFC PATCH v2 2/5] ASoC: soc-pcm: don't export local functions, use static

[Pierre-Louis Bossart]

No one uses the following functions outside of soc-pcm.c

snd_soc_dpcm_can_be_free_stop()
snd_soc_dpcm_can_be_params()
snd_soc_dpcm_be_can_update()

In preparation for locking changes, move them to static functions and
remove the EXPORT_SYMBOL_GPL()

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 include/sound/soc-dpcm.h | 12 ------------
 sound/soc/soc-pcm.c      | 21 +++++++++++++++------
 2 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/include/sound/soc-dpcm.h b/include/sound/soc-dpcm.h
index 72d45ad47ee3..9c00118603e7 100644
--- a/include/sound/soc-dpcm.h
+++ b/include/sound/soc-dpcm.h
@@ -113,18 +113,6 @@ struct snd_soc_dpcm_runtime {
 #define for_each_dpcm_be_rollback(fe, stream, _dpcm)			\
 	list_for_each_entry_continue_reverse(_dpcm, &(fe)->dpcm[stream].be_clients, list_be)
 
-/* can this BE stop and free */
-int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
-		struct snd_soc_pcm_runtime *be, int stream);
-
-/* can this BE perform a hw_params() */
-int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
-		struct snd_soc_pcm_runtime *be, int stream);
-
-/* is the current PCM operation for this BE ? */
-int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
-		struct snd_soc_pcm_runtime *be, int stream);
-
 /* get the substream for this BE */
 struct snd_pcm_substream *
 	snd_soc_dpcm_get_substream(struct snd_soc_pcm_runtime *be, int stream);
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 17476e3219ea..360811f8a18c 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -29,6 +29,18 @@
 
 #define DPCM_MAX_BE_USERS	8
 
+/* can this BE stop and free */
+static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
+					 struct snd_soc_pcm_runtime *be, int stream);
+
+/* can this BE perform a hw_params() */
+static int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
+				      struct snd_soc_pcm_runtime *be, int stream);
+
+/* is the current PCM operation for this BE ? */
+static int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
+				      struct snd_soc_pcm_runtime *be, int stream);
+
 static inline const char *soc_cpu_dai_name(struct snd_soc_pcm_runtime *rtd)
 {
 	return (rtd)->num_cpus == 1 ? asoc_rtd_to_cpu(rtd, 0)->name : "multicpu";
@@ -2806,7 +2818,7 @@ int soc_new_pcm(struct snd_soc_pcm_runtime *rtd, int num)
 }
 
 /* is the current PCM operation for this BE ? */
-int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
+static int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
 	if ((fe->dpcm[stream].runtime_update == SND_SOC_DPCM_UPDATE_FE) ||
@@ -2815,7 +2827,6 @@ int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
 		return 1;
 	return 0;
 }
-EXPORT_SYMBOL_GPL(snd_soc_dpcm_be_can_update);
 
 /* get the substream for this BE */
 struct snd_pcm_substream *
@@ -2861,7 +2872,7 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
  * We can only hw_free, stop, pause or suspend a BE DAI if any of it's FE
  * are not running, paused or suspended for the specified stream direction.
  */
-int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
+static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
 	const enum snd_soc_dpcm_state state[] = {
@@ -2872,13 +2883,12 @@ int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
 
 	return snd_soc_dpcm_check_state(fe, be, stream, state, ARRAY_SIZE(state));
 }
-EXPORT_SYMBOL_GPL(snd_soc_dpcm_can_be_free_stop);
 
 /*
  * We can only change hw params a BE DAI if any of it's FE are not prepared,
  * running, paused or suspended for the specified stream direction.
  */
-int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
+static int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
 	const enum snd_soc_dpcm_state state[] = {
@@ -2890,4 +2900,3 @@ int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
 
 	return snd_soc_dpcm_check_state(fe, be, stream, state, ARRAY_SIZE(state));
 }
-EXPORT_SYMBOL_GPL(snd_soc_dpcm_can_be_params);
-- 
2.25.1

[RFC PATCH v2 3/5] ASoC: soc-pcm: replace dpcm_lock with dpcm_mutex

[Pierre-Louis Bossart]

It's not clear why a spinlock was used, and even less why the
'dpcm_lock' is used with the irqsave/irqrestore: DPCM functions are
typically not used in interrupt context.

Move to a mutex which will allow us to sleep for longer periods of
time and handle non-atomic triggers.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 include/sound/soc.h  |  2 +-
 sound/soc/soc-core.c |  2 +-
 sound/soc/soc-pcm.c  | 30 ++++++++++++------------------
 3 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 8e6dd8a257c5..c13d8ec72d62 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -893,7 +893,7 @@ struct snd_soc_card {
 	struct mutex pcm_mutex;
 	enum snd_soc_pcm_subclass pcm_subclass;
 
-	spinlock_t dpcm_lock;
+	struct mutex dpcm_mutex; /* protect all dpcm states and updates */
 
 	int (*probe)(struct snd_soc_card *card);
 	int (*late_probe)(struct snd_soc_card *card);
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index c830e96afba2..e94d43c392e0 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2339,7 +2339,7 @@ int snd_soc_register_card(struct snd_soc_card *card)
 	mutex_init(&card->mutex);
 	mutex_init(&card->dapm_mutex);
 	mutex_init(&card->pcm_mutex);
-	spin_lock_init(&card->dpcm_lock);
+	mutex_init(&card->dpcm_mutex);
 
 	return snd_soc_bind_card(card);
 }
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 360811f8a18c..af12593b033a 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -85,7 +85,6 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe,
 	struct snd_pcm_hw_params *params = &fe->dpcm[stream].hw_params;
 	struct snd_soc_dpcm *dpcm;
 	ssize_t offset = 0;
-	unsigned long flags;
 
 	/* FE state */
 	offset += scnprintf(buf + offset, size - offset,
@@ -113,7 +112,7 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe,
 		goto out;
 	}
 
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		params = &dpcm->hw_params;
@@ -134,7 +133,7 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe,
 					   params_channels(params),
 					   params_rate(params));
 	}
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+	mutex_unlock(&fe->card->dpcm_mutex);
 out:
 	return offset;
 }
@@ -1141,7 +1140,6 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
 	struct snd_soc_dpcm *dpcm;
-	unsigned long flags;
 
 	/* only add new dpcms */
 	for_each_dpcm_be(fe, stream, dpcm) {
@@ -1157,10 +1155,10 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 	dpcm->fe = fe;
 	be->dpcm[stream].runtime = fe->dpcm[stream].runtime;
 	dpcm->state = SND_SOC_DPCM_LINK_STATE_NEW;
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+	mutex_lock(&fe->card->dpcm_mutex);
 	list_add(&dpcm->list_be, &fe->dpcm[stream].be_clients);
 	list_add(&dpcm->list_fe, &be->dpcm[stream].fe_clients);
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	dev_dbg(fe->dev, "connected new DPCM %s path %s %s %s\n",
 			stream ? "capture" : "playback",  fe->dai_link->name,
@@ -1203,7 +1201,6 @@ static void dpcm_be_reparent(struct snd_soc_pcm_runtime *fe,
 void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
 {
 	struct snd_soc_dpcm *dpcm, *d;
-	unsigned long flags;
 
 	for_each_dpcm_be_safe(fe, stream, dpcm, d) {
 		dev_dbg(fe->dev, "ASoC: BE %s disconnect check for %s\n",
@@ -1222,10 +1219,10 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
 
 		dpcm_remove_debugfs_state(dpcm);
 
-		spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+		mutex_lock(&fe->card->dpcm_mutex);
 		list_del(&dpcm->list_be);
 		list_del(&dpcm->list_fe);
-		spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+		mutex_unlock(&fe->card->dpcm_mutex);
 		kfree(dpcm);
 	}
 }
@@ -1441,12 +1438,11 @@ int dpcm_process_paths(struct snd_soc_pcm_runtime *fe,
 void dpcm_clear_pending_state(struct snd_soc_pcm_runtime *fe, int stream)
 {
 	struct snd_soc_dpcm *dpcm;
-	unsigned long flags;
 
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm)
 		dpcm_set_be_update_state(dpcm->be, stream, SND_SOC_DPCM_UPDATE_NO);
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
@@ -2364,7 +2360,6 @@ static int dpcm_run_update_startup(struct snd_soc_pcm_runtime *fe, int stream)
 	struct snd_soc_dpcm *dpcm;
 	enum snd_soc_dpcm_trigger trigger = fe->dai_link->trigger[stream];
 	int ret = 0;
-	unsigned long flags;
 
 	dev_dbg(fe->dev, "ASoC: runtime %s open on FE %s\n",
 			stream ? "capture" : "playback", fe->dai_link->name);
@@ -2433,7 +2428,7 @@ static int dpcm_run_update_startup(struct snd_soc_pcm_runtime *fe, int stream)
 	dpcm_be_dai_shutdown(fe, stream);
 disconnect:
 	/* disconnect any pending BEs */
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 
@@ -2445,7 +2440,7 @@ static int dpcm_run_update_startup(struct snd_soc_pcm_runtime *fe, int stream)
 			be->dpcm[stream].state == SND_SOC_DPCM_STATE_NEW)
 				dpcm->state = SND_SOC_DPCM_LINK_STATE_FREE;
 	}
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
@@ -2845,10 +2840,9 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 	struct snd_soc_dpcm *dpcm;
 	int state;
 	int ret = 1;
-	unsigned long flags;
 	int i;
 
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_fe(be, stream, dpcm) {
 
 		if (dpcm->fe == fe)
@@ -2862,7 +2856,7 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 			}
 		}
 	}
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	/* it's safe to do this BE DAI */
 	return ret;
-- 
2.25.1

[RFC PATCH v2 4/5] ASoC: soc-pcm: protect for_each_dpcm_be() loops with dpcm_mutex

[Pierre-Louis Bossart]

When more than one FE is connected to a BE, e.g. in a mixing use case,
the BE can be triggered multiple times when the FE are opened/started
concurrently. This race condition is problematic in the case of
SoundWire BE dailinks, and this is not desirable in a general
case. The code carefully checks when the BE can be stopped or
hw_free'ed, but the trigger code does not use any mutual exclusion.

This can be fixed by using the dpcm_mutex.

As discussed on the alsa-mailing list [1], there is an additional
issue that the BEs can be disconnected dynamically, leading to
potential accesses to freed memory.

This patch suggests a general protection of the for_each_dpcm_be()
loop with the dpcm_mutex, to solve both the problem of multiple
triggers and BE dynamic addition/removal.

[1] https://lore.kernel.org/alsa-devel/002f01d7b4f5$c030f4a0$4092dde0$@samsung.com/

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 sound/soc/soc-pcm.c | 48 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index af12593b033a..6089e0c1bf9f 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -320,6 +320,7 @@ int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
 {
 	struct snd_soc_dpcm *dpcm;
 
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, dir, dpcm) {
 
 		struct snd_soc_pcm_runtime *be = dpcm->be;
@@ -333,6 +334,8 @@ int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
 
 		snd_soc_dapm_stream_event(be, dir, event);
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
+
 
 	snd_soc_dapm_stream_event(fe, dir, event);
 
@@ -1142,10 +1145,14 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 	struct snd_soc_dpcm *dpcm;
 
 	/* only add new dpcms */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
-		if (dpcm->be == be && dpcm->fe == fe)
+		if (dpcm->be == be && dpcm->fe == fe) {
+			mutex_unlock(&fe->card->dpcm_mutex);
 			return 0;
+		}
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	dpcm = kzalloc(sizeof(struct snd_soc_dpcm), GFP_KERNEL);
 	if (!dpcm)
@@ -1202,6 +1209,7 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
 {
 	struct snd_soc_dpcm *dpcm, *d;
 
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be_safe(fe, stream, dpcm, d) {
 		dev_dbg(fe->dev, "ASoC: BE %s disconnect check for %s\n",
 				stream ? "capture" : "playback",
@@ -1219,12 +1227,11 @@ void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream)
 
 		dpcm_remove_debugfs_state(dpcm);
 
-		mutex_lock(&fe->card->dpcm_mutex);
 		list_del(&dpcm->list_be);
 		list_del(&dpcm->list_fe);
-		mutex_unlock(&fe->card->dpcm_mutex);
 		kfree(dpcm);
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 /* get BE for DAI widget and stream */
@@ -1351,6 +1358,7 @@ static int dpcm_prune_paths(struct snd_soc_pcm_runtime *fe, int stream,
 	int prune = 0;
 
 	/* Destroy any old FE <--> BE connections */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		if (dpcm_be_is_active(dpcm, stream, *list_))
 			continue;
@@ -1362,6 +1370,7 @@ static int dpcm_prune_paths(struct snd_soc_pcm_runtime *fe, int stream,
 		dpcm_set_be_update_state(dpcm->be, stream, SND_SOC_DPCM_UPDATE_BE);
 		prune++;
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	dev_dbg(fe->dev, "ASoC: found %d old BE paths for pruning\n", prune);
 	return prune;
@@ -1451,13 +1460,16 @@ void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
 	struct snd_soc_dpcm *dpcm;
 
 	/* disable any enabled and non active backends */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_pcm_substream *be_substream =
 			snd_soc_dpcm_get_substream(be, stream);
 
-		if (dpcm == last)
+		if (dpcm == last) {
+			mutex_unlock(&fe->card->dpcm_mutex);
 			return;
+		}
 
 		/* is this op for this BE ? */
 		if (!snd_soc_dpcm_be_can_update(fe, be, stream))
@@ -1487,6 +1499,7 @@ void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
 		be_substream->runtime = NULL;
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_CLOSE;
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
@@ -1496,6 +1509,7 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
 	int err, count = 0;
 
 	/* only startup BE DAIs that are either sinks or sources to this FE DAI */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_pcm_substream *be_substream;
 
@@ -1546,11 +1560,13 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
 		count++;
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	return count;
 
 unwind:
 	dpcm_be_dai_startup_rollback(fe, stream, dpcm);
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	dev_err(fe->dev, "ASoC: %s() failed at %s (%d)\n",
 		__func__, be->dai_link->name, err);
@@ -1605,6 +1621,7 @@ static void dpcm_runtime_setup_be_format(struct snd_pcm_substream *substream)
 	 * if FE want to use it (= dpcm_merged_format)
 	 */
 
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_soc_pcm_stream *codec_stream;
@@ -1623,6 +1640,7 @@ static void dpcm_runtime_setup_be_format(struct snd_pcm_substream *substream)
 			soc_pcm_hw_update_format(hw, codec_stream);
 		}
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
@@ -1640,7 +1658,7 @@ static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
 	 * It returns merged BE codec channel;
 	 * if FE want to use it (= dpcm_merged_chan)
 	 */
-
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_soc_pcm_stream *cpu_stream;
@@ -1671,6 +1689,7 @@ static void dpcm_runtime_setup_be_chan(struct snd_pcm_substream *substream)
 			soc_pcm_hw_update_chan(hw, codec_stream);
 		}
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
@@ -1688,7 +1707,7 @@ static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
 	 * It returns merged BE codec channel;
 	 * if FE want to use it (= dpcm_merged_chan)
 	 */
-
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_soc_pcm_stream *pcm;
@@ -1708,6 +1727,7 @@ static void dpcm_runtime_setup_be_rate(struct snd_pcm_substream *substream)
 			soc_pcm_hw_update_rate(hw, pcm);
 		}
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
@@ -1730,6 +1750,7 @@ static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
 	}
 
 	/* apply symmetry for BE */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		struct snd_pcm_substream *be_substream =
@@ -1755,6 +1776,7 @@ static int dpcm_apply_symmetry(struct snd_pcm_substream *fe_substream,
 		}
 	}
 error:
+	mutex_unlock(&fe->card->dpcm_mutex);
 	if (err < 0)
 		dev_err(fe->dev, "ASoC: %s failed (%d)\n", __func__, err);
 
@@ -1830,6 +1852,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
 
 	/* only hw_params backends that are either sinks or sources
 	 * to this frontend DAI */
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 
 		struct snd_soc_pcm_runtime *be = dpcm->be;
@@ -1842,7 +1865,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
 
 		/* only free hw when no longer used - check all FEs */
 		if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
-				continue;
+			continue;
 
 		/* do not free hw if this BE is used by other FE */
 		if (be->dpcm[stream].users > 1)
@@ -1863,6 +1886,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
 
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_FREE;
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 }
 
 static int dpcm_fe_dai_hw_free(struct snd_pcm_substream *substream)
@@ -1896,6 +1920,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
 	struct snd_soc_dpcm *dpcm;
 	int ret;
 
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		be = dpcm->be;
 		be_substream = snd_soc_dpcm_get_substream(be, stream);
@@ -1935,6 +1960,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
 
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_PARAMS;
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 	return 0;
 
 unwind:
@@ -1961,6 +1987,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
 
 		soc_pcm_hw_free(be_substream);
 	}
+	mutex_unlock(&fe->card->dpcm_mutex);
 
 	return ret;
 }
@@ -2008,6 +2035,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 	struct snd_soc_dpcm *dpcm;
 	int ret = 0;
 
+	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_pcm_substream *be_substream;
 
@@ -2097,6 +2125,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 		}
 	}
 end:
+	mutex_unlock(&fe->card->dpcm_mutex);
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s() failed at %s (%d)\n",
 			__func__, be->dai_link->name, ret);
@@ -2831,6 +2860,7 @@ struct snd_pcm_substream *
 }
 EXPORT_SYMBOL_GPL(snd_soc_dpcm_get_substream);
 
+/* This must be called with fe->card->dpcm_mutex held */
 static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 				    struct snd_soc_pcm_runtime *be,
 				    int stream,
@@ -2842,7 +2872,6 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 	int ret = 1;
 	int i;
 
-	mutex_lock(&fe->card->dpcm_mutex);
 	for_each_dpcm_fe(be, stream, dpcm) {
 
 		if (dpcm->fe == fe)
@@ -2856,7 +2885,6 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 			}
 		}
 	}
-	mutex_unlock(&fe->card->dpcm_mutex);
 
 	/* it's safe to do this BE DAI */
 	return ret;
@@ -2865,6 +2893,7 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 /*
  * We can only hw_free, stop, pause or suspend a BE DAI if any of it's FE
  * are not running, paused or suspended for the specified stream direction.
+ * This must be called with fe->card->dpcm_mutex held.
  */
 static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
@@ -2881,6 +2910,7 @@ static int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
 /*
  * We can only change hw params a BE DAI if any of it's FE are not prepared,
  * running, paused or suspended for the specified stream direction.
+ * This must be called with fe->card->dpcm_mutex held.
  */
 static int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
-- 
2.25.1

[RFC PATCH v2 5/5] ASoC: soc-pcm: test refcount before triggering

[Pierre-Louis Bossart]

On start/pause_release/resume, when more than one FE is connected to
the same BE, it's possible that the trigger is sent more than
once. This is not desirable, we only want to trigger a BE once, which
is straightforward to implement with a refcount.

For stop/pause/suspend, the problem is more complicated: the check
implemented in snd_soc_dpcm_can_be_free_stop() may fail due to a
conceptual deadlock when we trigger the BE before the FE. In this
case, the FE states have not yet changed, so there are corner cases
where the TRIGGER_STOP is never sent - the dual case of start where
multiple triggers might be sent.

This patch suggests an unconditional trigger in all cases, without
checking the FE states, using a refcount protected by a mutex.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
---
 include/sound/soc-dpcm.h |  2 ++
 sound/soc/soc-pcm.c      | 53 +++++++++++++++++++++++++++++++---------
 2 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/include/sound/soc-dpcm.h b/include/sound/soc-dpcm.h
index 9c00118603e7..6d84e2c60ca8 100644
--- a/include/sound/soc-dpcm.h
+++ b/include/sound/soc-dpcm.h
@@ -101,6 +101,8 @@ struct snd_soc_dpcm_runtime {
 	enum snd_soc_dpcm_state state;
 
 	int trigger_pending; /* trigger cmd + 1 if pending, 0 if not */
+
+	int be_start; /* refcount protected by card's dpcm_mutex */
 };
 
 #define for_each_dpcm_fe(be, stream, _dpcm)				\
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 6089e0c1bf9f..ed898d83fe17 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1556,7 +1556,7 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_CLOSE;
 			goto unwind;
 		}
-
+		be->dpcm[stream].be_start = 0;
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_OPEN;
 		count++;
 	}
@@ -2051,14 +2051,21 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 
 		switch (cmd) {
 		case SNDRV_PCM_TRIGGER_START:
-			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PREPARE) &&
+			if (!be->dpcm[stream].be_start &&
+			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PREPARE) &&
 			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP) &&
 			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
 				continue;
 
+			be->dpcm[stream].be_start++;
+			if (be->dpcm[stream].be_start != 1)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				be->dpcm[stream].be_start--;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
@@ -2066,9 +2073,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_SUSPEND))
 				continue;
 
+			be->dpcm[stream].be_start++;
+			if (be->dpcm[stream].be_start != 1)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				be->dpcm[stream].be_start--;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
@@ -2076,9 +2089,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
 				continue;
 
+			be->dpcm[stream].be_start++;
+			if (be->dpcm[stream].be_start != 1)
+				continue;
+
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				be->dpcm[stream].be_start--;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
@@ -2087,12 +2106,18 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
 				continue;
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			if (be->dpcm[stream].state == SND_SOC_DPCM_STATE_START)
+				be->dpcm[stream].be_start--;
+
+			if (be->dpcm[stream].be_start != 0)
 				continue;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				if (be->dpcm[stream].state == SND_SOC_DPCM_STATE_START)
+					be->dpcm[stream].be_start++;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_STOP;
 			break;
@@ -2100,12 +2125,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
 				continue;
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			be->dpcm[stream].be_start--;
+			if (be->dpcm[stream].be_start != 0)
 				continue;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				be->dpcm[stream].be_start++;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_SUSPEND;
 			break;
@@ -2113,12 +2141,15 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
 				continue;
 
-			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
+			be->dpcm[stream].be_start--;
+			if (be->dpcm[stream].be_start != 0)
 				continue;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
-			if (ret)
+			if (ret) {
+				be->dpcm[stream].be_start++;
 				goto end;
+			}
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_PAUSED;
 			break;
-- 
2.25.1