Re: [RFC PATCH v3 05/13] ASoC: soc-pcm: align BE 'atomicity' with that of the FE

[Takashi Iwai <tiwai@suse.de>]

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On Fri, 15 Oct 2021 13:22:50 +0200,
Pierre-Louis Bossart wrote:
> 
> >> At this point it does not cause serious problems, but with subsequent
> >> patches (especially when patch 7/13 is picked) I see failures. Please
> >> refer to patch 7/13 thread for more details.
> >>
> >>
> >> I am wondering if it is possible to only use locks internally for DPCM
> >> state management and decouple BE callbacks from this, like normal PCMs
> >> do?
> > 
> > Actually the patch looks like an overkill by adding the FE stream lock
> > at every loop, and this caused the problem, AFAIU.
> > 
> > Basically we need to protect the link addition / deletion while the
> > list traversal (there is a need for protection of BE vs BE access
> > race, but that's a different code path).  For the normal cases, it
> > seems already protected by card->pcm_mutex, but the problem is the FE
> > trigger case.  It was attempted by dpcm_lock, but that failed because
> > it couldn't be applied properly there.
> > 
> > That said, what we'd need is only:
> > - Drop dpcm_lock codes once
> 
> I am not able to follow this sentence, what did you mean here?

Just remove all dpcm_lock usages one to replace with a new one.

> > - Put FE stream lock around dpcm_be_connect() and dpcm_be_disconnect()
> > 
> > That should suffice for the race at trigger.  The FE stream lock is
> > already taken at trigger callback, and the rest list addition /
> > deletion are called from different code paths without stream locks, so
> > the explicit FE stream lock is needed there.
> 
> I am not able to follow what you meant after "the rest". This sentence
> mentions the FE stream lock in two places, but the second is not clear
> to me.

The FE stream locks are necessary only two points: at adding and
deleting the BE in the link.  We used dpcm_lock in other places, but
those are superfluous or would make problem if converted to a FE
stream lock.

> > In addition, a lock around dpcm_show_state() might be needed to be
> > replaced with card->pcm_mutex, and we may need to revisit whether all
> > other paths take card->pcm_mutex.
> 
> What happens if we show the state while a trigger happens? That's my
> main concern with using two separate locks (pcm_mutex and FE stream
> lock) to protect the same list, there are still windows of time where
> the list is not protected.

With the proper use of mutex, the list itself is protected.
If we need to protect the concurrent access to each BE in the show
method, an additional BE lock is needed in that part.  But that's a
subtle issue, as the link traversal itself is protected by the mutex.

> same with the use of for_each_dpcm_be() in soc-compress, SH and FSL
> drivers, there's no other mutex there.
> 
> My approach might have been overkill in some places, but it's comprehensive.
> 
> 
> > Also, BE-vs-BE race can be protected by taking a BE lock inside
> > dpcm_be_dai_trigger().
> 
> that's what I did, no?

Right.

So what I wrote is like the patches below.  Those three should be
applicable on top of the latest Linus tree.  It's merely a PoC, and it
doesn't take the compress-offload usage into account at all, but this
should illustrate my idea.


Takashi


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From f2c1fb7835e881650dbf24781a29844cf0c0c2b9 Mon Sep 17 00:00:00 2001
From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Date: Wed, 13 Oct 2021 09:30:42 -0500
Subject: [PATCH 1/3] ASoC: soc-pcm: align BE 'atomicity' with that of the FE

Since the flow for DPCM is based on taking a lock for the FE first, we
need to make sure during the connection between a BE and an FE that
they both use the same 'atomicity', otherwise we may sleep in atomic
context.

If the FE is nonatomic, this patch forces the BE to be nonatomic as
well. That should have no negative impact since the BE 'inherits' the
FE properties.

However, if the FE is atomic and the BE is not, then the configuration
is flagged as invalid.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
[ removed FE stream lock by tiwai ]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/soc/soc-pcm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 48f71bb81a2f..d4a711c09eb5 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1128,6 +1128,8 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
 static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 		struct snd_soc_pcm_runtime *be, int stream)
 {
+	struct snd_pcm_substream *fe_substream;
+	struct snd_pcm_substream *be_substream;
 	struct snd_soc_dpcm *dpcm;
 	unsigned long flags;
 
@@ -1137,6 +1139,20 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 			return 0;
 	}
 
+	fe_substream = snd_soc_dpcm_get_substream(fe, stream);
+	be_substream = snd_soc_dpcm_get_substream(be, stream);
+
+	if (!fe_substream->pcm->nonatomic && be_substream->pcm->nonatomic) {
+		dev_err(be->dev, "%s: FE is atomic but BE is nonatomic, invalid configuration\n",
+			__func__);
+		return -EINVAL;
+	}
+	if (fe_substream->pcm->nonatomic && !be_substream->pcm->nonatomic) {
+		dev_warn(be->dev, "%s: FE is nonatomic but BE is not, forcing BE as nonatomic\n",
+			 __func__);
+		be_substream->pcm->nonatomic = 1;
+	}
+
 	dpcm = kzalloc(sizeof(struct snd_soc_dpcm), GFP_KERNEL);
 	if (!dpcm)
 		return -ENOMEM;
-- 
2.31.1


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From 1ca313d8b98a844540d97b4605cbe05917961182 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Fri, 15 Oct 2021 17:11:10 +0200
Subject: [PATCH 2/3] ASoC: DPCM: Fix and cleanup PCM locking

Use card->pcm_mutex consistently instead of mixture of card->mutex and
card->pcm_mutex.  This is used for protecting the BE link in each FE.

Replace the half-baked dpcm_lock spinlock with the PCM stream lock of
each FE for protecting the BE link in addition to the pcm_mutex
above for avoiding the race in FE trigger.  The additional FE stream
locks are taken only at adding and deleting the BE link entries.

The pcm_mutex is applied always on either the top PCM callbacks or the
external call from DAPM, not taken in the internal functions.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/soc.h  |   2 -
 sound/soc/soc-core.c |   1 -
 sound/soc/soc-pcm.c  | 229 ++++++++++++++++++++++++++++---------------
 3 files changed, 152 insertions(+), 80 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 8e6dd8a257c5..5872a8864f3b 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -893,8 +893,6 @@ struct snd_soc_card {
 	struct mutex pcm_mutex;
 	enum snd_soc_pcm_subclass pcm_subclass;
 
-	spinlock_t dpcm_lock;
-
 	int (*probe)(struct snd_soc_card *card);
 	int (*late_probe)(struct snd_soc_card *card);
 	int (*remove)(struct snd_soc_card *card);
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index c830e96afba2..51ef9917ca98 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2339,7 +2339,6 @@ 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);
 
 	return snd_soc_bind_card(card);
 }
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index d4a711c09eb5..5bd4f953359a 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -27,6 +27,31 @@
 #include <sound/soc-link.h>
 #include <sound/initval.h>
 
+static inline void snd_soc_dpcm_mutex_lock(struct snd_soc_pcm_runtime *rtd)
+{
+	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+}
+
+static inline void snd_soc_dpcm_mutex_unlock(struct snd_soc_pcm_runtime *rtd)
+{
+	mutex_unlock(&rtd->card->pcm_mutex);
+}
+
+#define snd_soc_dpcm_mutex_assert_held(rtd) \
+	lockdep_assert_held(&(rtd)->card->pcm_mutex)
+
+static inline void snd_soc_dpcm_stream_lock_irq(struct snd_soc_pcm_runtime *rtd,
+						int stream)
+{
+	snd_pcm_stream_lock_irq(snd_soc_dpcm_get_substream(rtd, stream));
+}
+
+static inline void snd_soc_dpcm_stream_unlock_irq(struct snd_soc_pcm_runtime *rtd,
+						  int stream)
+{
+	snd_pcm_stream_unlock_irq(snd_soc_dpcm_get_substream(rtd, stream));
+}
+
 #define DPCM_MAX_BE_USERS	8
 
 static inline const char *soc_cpu_dai_name(struct snd_soc_pcm_runtime *rtd)
@@ -73,7 +98,6 @@ 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,
@@ -101,7 +125,6 @@ static ssize_t dpcm_show_state(struct snd_soc_pcm_runtime *fe,
 		goto out;
 	}
 
-	spin_lock_irqsave(&fe->card->dpcm_lock, flags);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 		params = &dpcm->hw_params;
@@ -122,7 +145,6 @@ 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);
 out:
 	return offset;
 }
@@ -145,11 +167,13 @@ static ssize_t dpcm_state_read_file(struct file *file, char __user *user_buf,
 	if (!buf)
 		return -ENOMEM;
 
+	snd_soc_dpcm_mutex_lock(fe);
 	for_each_pcm_streams(stream)
 		if (snd_soc_dai_stream_valid(asoc_rtd_to_cpu(fe, 0), stream))
 			offset += dpcm_show_state(fe, stream,
 						  buf + offset,
 						  out_count - offset);
+	snd_soc_dpcm_mutex_unlock(fe);
 
 	ret = simple_read_from_buffer(user_buf, count, ppos, buf, offset);
 
@@ -221,14 +245,14 @@ static void dpcm_set_fe_update_state(struct snd_soc_pcm_runtime *fe,
 	struct snd_pcm_substream *substream =
 		snd_soc_dpcm_get_substream(fe, stream);
 
-	snd_pcm_stream_lock_irq(substream);
+	snd_soc_dpcm_stream_lock_irq(fe, stream);
 	if (state == SND_SOC_DPCM_UPDATE_NO && fe->dpcm[stream].trigger_pending) {
 		dpcm_fe_dai_do_trigger(substream,
 				       fe->dpcm[stream].trigger_pending - 1);
 		fe->dpcm[stream].trigger_pending = 0;
 	}
 	fe->dpcm[stream].runtime_update = state;
-	snd_pcm_stream_unlock_irq(substream);
+	snd_soc_dpcm_stream_unlock_irq(fe, stream);
 }
 
 static void dpcm_set_be_update_state(struct snd_soc_pcm_runtime *be,
@@ -256,7 +280,7 @@ void snd_soc_runtime_action(struct snd_soc_pcm_runtime *rtd,
 	struct snd_soc_dai *dai;
 	int i;
 
-	lockdep_assert_held(&rtd->card->pcm_mutex);
+	snd_soc_dpcm_mutex_assert_held(rtd);
 
 	for_each_rtd_dais(rtd, i, dai)
 		snd_soc_dai_action(dai, stream, action);
@@ -309,6 +333,8 @@ int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
 {
 	struct snd_soc_dpcm *dpcm;
 
+	snd_soc_dpcm_mutex_assert_held(fe);
+
 	for_each_dpcm_be(fe, dir, dpcm) {
 
 		struct snd_soc_pcm_runtime *be = dpcm->be;
@@ -646,14 +672,14 @@ static int soc_pcm_components_close(struct snd_pcm_substream *substream,
 	return ret;
 }
 
-static int soc_pcm_clean(struct snd_pcm_substream *substream, int rollback)
+static int soc_pcm_clean(struct snd_soc_pcm_runtime *rtd,
+			 struct snd_pcm_substream *substream, int rollback)
 {
-	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_component *component;
 	struct snd_soc_dai *dai;
 	int i;
 
-	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+	snd_soc_dpcm_mutex_assert_held(rtd);
 
 	if (!rollback)
 		snd_soc_runtime_deactivate(rtd, substream->stream);
@@ -665,9 +691,6 @@ static int soc_pcm_clean(struct snd_pcm_substream *substream, int rollback)
 
 	soc_pcm_components_close(substream, rollback);
 
-
-	mutex_unlock(&rtd->card->pcm_mutex);
-
 	snd_soc_pcm_component_pm_runtime_put(rtd, substream, rollback);
 
 	for_each_rtd_components(rtd, i, component)
@@ -682,9 +705,21 @@ static int soc_pcm_clean(struct snd_pcm_substream *substream, int rollback)
  * freed here. The cpu DAI, codec DAI, machine and components are also
  * shutdown.
  */
+static int __soc_pcm_close(struct snd_soc_pcm_runtime *rtd,
+			   struct snd_pcm_substream *substream)
+{
+	return soc_pcm_clean(rtd, substream, 0);
+}
+
+/* PCM close ops for non-DPCM streams */
 static int soc_pcm_close(struct snd_pcm_substream *substream)
 {
-	return soc_pcm_clean(substream, 0);
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+
+	snd_soc_dpcm_mutex_lock(rtd);
+	soc_pcm_clean(rtd, substream, 0);
+	snd_soc_dpcm_mutex_unlock(rtd);
+	return 0;
 }
 
 static int soc_hw_sanity_check(struct snd_pcm_substream *substream)
@@ -730,21 +765,21 @@ static int soc_hw_sanity_check(struct snd_pcm_substream *substream)
  * then initialized and any private data can be allocated. This also calls
  * startup for the cpu DAI, component, machine and codec DAI.
  */
-static int soc_pcm_open(struct snd_pcm_substream *substream)
+static int __soc_pcm_open(struct snd_soc_pcm_runtime *rtd,
+			  struct snd_pcm_substream *substream)
 {
-	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_component *component;
 	struct snd_soc_dai *dai;
 	int i, ret = 0;
 
+	snd_soc_dpcm_mutex_assert_held(rtd);
+
 	for_each_rtd_components(rtd, i, component)
 		pinctrl_pm_select_default_state(component->dev);
 
 	ret = snd_soc_pcm_component_pm_runtime_get(rtd, substream);
 	if (ret < 0)
-		goto pm_err;
-
-	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+		goto err;
 
 	ret = soc_pcm_components_open(substream);
 	if (ret < 0)
@@ -791,16 +826,26 @@ static int soc_pcm_open(struct snd_pcm_substream *substream)
 	snd_soc_runtime_activate(rtd, substream->stream);
 	ret = 0;
 err:
-	mutex_unlock(&rtd->card->pcm_mutex);
-pm_err:
 	if (ret < 0) {
-		soc_pcm_clean(substream, 1);
+		soc_pcm_clean(rtd, substream, 1);
 		dev_err(rtd->dev, "%s() failed (%d)", __func__, ret);
 	}
 
 	return ret;
 }
 
+/* PCM open ops for non-DPCM streams */
+static int soc_pcm_open(struct snd_pcm_substream *substream)
+{
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	int ret;
+
+	snd_soc_dpcm_mutex_lock(rtd);
+	ret = __soc_pcm_open(rtd, substream);
+	snd_soc_dpcm_mutex_unlock(rtd);
+	return ret;
+}
+
 static void codec2codec_close_delayed_work(struct snd_soc_pcm_runtime *rtd)
 {
 	/*
@@ -816,13 +861,13 @@ static void codec2codec_close_delayed_work(struct snd_soc_pcm_runtime *rtd)
  * rate, etc.  This function is non atomic and can be called multiple times,
  * it can refer to the runtime info.
  */
-static int soc_pcm_prepare(struct snd_pcm_substream *substream)
+static int __soc_pcm_prepare(struct snd_soc_pcm_runtime *rtd,
+			     struct snd_pcm_substream *substream)
 {
-	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_dai *dai;
 	int i, ret = 0;
 
-	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+	snd_soc_dpcm_mutex_assert_held(rtd);
 
 	ret = snd_soc_link_prepare(substream);
 	if (ret < 0)
@@ -850,14 +895,24 @@ static int soc_pcm_prepare(struct snd_pcm_substream *substream)
 		snd_soc_dai_digital_mute(dai, 0, substream->stream);
 
 out:
-	mutex_unlock(&rtd->card->pcm_mutex);
-
 	if (ret < 0)
 		dev_err(rtd->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
 
 	return ret;
 }
 
+/* PCM prepare ops for non-DPCM streams */
+static int soc_pcm_prepare(struct snd_pcm_substream *substream)
+{
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	int ret;
+
+	snd_soc_dpcm_mutex_lock(rtd);
+	ret = __soc_pcm_prepare(rtd, substream);
+	snd_soc_dpcm_mutex_unlock(rtd);
+	return ret;
+}
+
 static void soc_pcm_codec_params_fixup(struct snd_pcm_hw_params *params,
 				       unsigned int mask)
 {
@@ -869,13 +924,13 @@ static void soc_pcm_codec_params_fixup(struct snd_pcm_hw_params *params,
 	interval->max = channels;
 }
 
-static int soc_pcm_hw_clean(struct snd_pcm_substream *substream, int rollback)
+static int soc_pcm_hw_clean(struct snd_soc_pcm_runtime *rtd,
+			    struct snd_pcm_substream *substream, int rollback)
 {
-	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_dai *dai;
 	int i;
 
-	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+	snd_soc_dpcm_mutex_assert_held(rtd);
 
 	/* clear the corresponding DAIs parameters when going to be inactive */
 	for_each_rtd_dais(rtd, i, dai) {
@@ -905,16 +960,28 @@ static int soc_pcm_hw_clean(struct snd_pcm_substream *substream, int rollback)
 		snd_soc_dai_hw_free(dai, substream, rollback);
 	}
 
-	mutex_unlock(&rtd->card->pcm_mutex);
 	return 0;
 }
 
 /*
  * Frees resources allocated by hw_params, can be called multiple times
  */
+static int __soc_pcm_hw_free(struct snd_soc_pcm_runtime *rtd,
+			     struct snd_pcm_substream *substream)
+{
+	return soc_pcm_hw_clean(rtd, substream, 0);
+}
+
+/* hw_free PCM ops for non-DPCM streams */
 static int soc_pcm_hw_free(struct snd_pcm_substream *substream)
 {
-	return soc_pcm_hw_clean(substream, 0);
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	int ret;
+
+	snd_soc_dpcm_mutex_lock(rtd);
+	ret = __soc_pcm_hw_free(rtd, substream);
+	snd_soc_dpcm_mutex_unlock(rtd);
+	return ret;
 }
 
 /*
@@ -922,15 +989,15 @@ static int soc_pcm_hw_free(struct snd_pcm_substream *substream)
  * function can also be called multiple times and can allocate buffers
  * (using snd_pcm_lib_* ). It's non-atomic.
  */
-static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
-				struct snd_pcm_hw_params *params)
+static int __soc_pcm_hw_params(struct snd_soc_pcm_runtime *rtd,
+			       struct snd_pcm_substream *substream,
+			       struct snd_pcm_hw_params *params)
 {
-	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
 	struct snd_soc_dai *cpu_dai;
 	struct snd_soc_dai *codec_dai;
 	int i, ret = 0;
 
-	mutex_lock_nested(&rtd->card->pcm_mutex, rtd->card->pcm_subclass);
+	snd_soc_dpcm_mutex_assert_held(rtd);
 
 	ret = soc_pcm_params_symmetry(substream, params);
 	if (ret)
@@ -1002,16 +1069,27 @@ static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
 
 	ret = snd_soc_pcm_component_hw_params(substream, params);
 out:
-	mutex_unlock(&rtd->card->pcm_mutex);
-
 	if (ret < 0) {
-		soc_pcm_hw_clean(substream, 1);
+		soc_pcm_hw_clean(rtd, substream, 1);
 		dev_err(rtd->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
 	}
 
 	return ret;
 }
 
+/* hw_params PCM ops for non-DPCM streams */
+static int soc_pcm_hw_params(struct snd_pcm_substream *substream,
+			     struct snd_pcm_hw_params *params)
+{
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	int ret;
+
+	snd_soc_dpcm_mutex_lock(rtd);
+	ret = __soc_pcm_hw_params(rtd, substream, params);
+	snd_soc_dpcm_mutex_unlock(rtd);
+	return ret;
+}
+
 static int soc_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 {
 	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
@@ -1131,7 +1209,8 @@ static int dpcm_be_connect(struct snd_soc_pcm_runtime *fe,
 	struct snd_pcm_substream *fe_substream;
 	struct snd_pcm_substream *be_substream;
 	struct snd_soc_dpcm *dpcm;
-	unsigned long flags;
+
+	snd_soc_dpcm_mutex_assert_held(fe);
 
 	/* only add new dpcms */
 	for_each_dpcm_be(fe, stream, dpcm) {
@@ -1161,10 +1240,10 @@ 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);
+	snd_soc_dpcm_stream_lock_irq(fe, stream);
 	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);
+	snd_soc_dpcm_stream_unlock_irq(fe, stream);
 
 	dev_dbg(fe->dev, "connected new DPCM %s path %s %s %s\n",
 			stream ? "capture" : "playback",  fe->dai_link->name,
@@ -1207,8 +1286,10 @@ 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;
 
+	snd_soc_dpcm_mutex_assert_held(fe);
+
+	snd_soc_dpcm_stream_lock_irq(fe, stream);
 	for_each_dpcm_be_safe(fe, stream, dpcm, d) {
 		dev_dbg(fe->dev, "ASoC: BE %s disconnect check for %s\n",
 				stream ? "capture" : "playback",
@@ -1226,12 +1307,11 @@ 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);
 		list_del(&dpcm->list_be);
 		list_del(&dpcm->list_fe);
-		spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 		kfree(dpcm);
 	}
+	snd_soc_dpcm_stream_unlock_irq(fe, stream);
 }
 
 /* get BE for DAI widget and stream */
@@ -1445,12 +1525,9 @@ 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);
 	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);
 }
 
 void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
@@ -1486,12 +1563,12 @@ void dpcm_be_dai_stop(struct snd_soc_pcm_runtime *fe, int stream,
 				continue;
 
 			if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_HW_FREE) {
-				soc_pcm_hw_free(be_substream);
+				__soc_pcm_hw_free(be, be_substream);
 				be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_FREE;
 			}
 		}
 
-		soc_pcm_close(be_substream);
+		__soc_pcm_close(be, be_substream);
 		be_substream->runtime = NULL;
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_CLOSE;
 	}
@@ -1539,7 +1616,7 @@ int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream)
 			stream ? "capture" : "playback", be->dai_link->name);
 
 		be_substream->runtime = be->dpcm[stream].runtime;
-		err = soc_pcm_open(be_substream);
+		err = __soc_pcm_open(be, be_substream);
 		if (err < 0) {
 			be->dpcm[stream].users--;
 			if (be->dpcm[stream].users < 0)
@@ -1783,7 +1860,7 @@ static int dpcm_fe_dai_startup(struct snd_pcm_substream *fe_substream)
 	dev_dbg(fe->dev, "ASoC: open FE %s\n", fe->dai_link->name);
 
 	/* start the DAI frontend */
-	ret = soc_pcm_open(fe_substream);
+	ret = __soc_pcm_open(fe, fe_substream);
 	if (ret < 0)
 		goto unwind;
 
@@ -1814,6 +1891,8 @@ static int dpcm_fe_dai_shutdown(struct snd_pcm_substream *substream)
 	struct snd_soc_pcm_runtime *fe = asoc_substream_to_rtd(substream);
 	int stream = substream->stream;
 
+	snd_soc_dpcm_mutex_assert_held(fe);
+
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_FE);
 
 	/* shutdown the BEs */
@@ -1822,7 +1901,7 @@ static int dpcm_fe_dai_shutdown(struct snd_pcm_substream *substream)
 	dev_dbg(fe->dev, "ASoC: close FE %s\n", fe->dai_link->name);
 
 	/* now shutdown the frontend */
-	soc_pcm_close(substream);
+	__soc_pcm_close(fe, substream);
 
 	/* run the stream stop event */
 	dpcm_dapm_stream_event(fe, stream, SND_SOC_DAPM_STREAM_STOP);
@@ -1867,7 +1946,7 @@ void dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream)
 		dev_dbg(be->dev, "ASoC: hw_free BE %s\n",
 			be->dai_link->name);
 
-		soc_pcm_hw_free(be_substream);
+		__soc_pcm_hw_free(be, be_substream);
 
 		be->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_FREE;
 	}
@@ -1878,13 +1957,13 @@ static int dpcm_fe_dai_hw_free(struct snd_pcm_substream *substream)
 	struct snd_soc_pcm_runtime *fe = asoc_substream_to_rtd(substream);
 	int stream = substream->stream;
 
-	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	snd_soc_dpcm_mutex_lock(fe);
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_FE);
 
 	dev_dbg(fe->dev, "ASoC: hw_free FE %s\n", fe->dai_link->name);
 
 	/* call hw_free on the frontend */
-	soc_pcm_hw_free(substream);
+	soc_pcm_hw_clean(fe, substream, 0);
 
 	/* only hw_params backends that are either sinks or sources
 	 * to this frontend DAI */
@@ -1893,7 +1972,7 @@ static int dpcm_fe_dai_hw_free(struct snd_pcm_substream *substream)
 	fe->dpcm[stream].state = SND_SOC_DPCM_STATE_HW_FREE;
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_NO);
 
-	mutex_unlock(&fe->card->mutex);
+	snd_soc_dpcm_mutex_unlock(fe);
 	return 0;
 }
 
@@ -1937,7 +2016,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
 		dev_dbg(be->dev, "ASoC: hw_params BE %s\n",
 			be->dai_link->name);
 
-		ret = soc_pcm_hw_params(be_substream, &dpcm->hw_params);
+		ret = __soc_pcm_hw_params(be, be_substream, &dpcm->hw_params);
 		if (ret < 0)
 			goto unwind;
 
@@ -1967,7 +2046,7 @@ int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int stream)
 		   (be->dpcm[stream].state != SND_SOC_DPCM_STATE_STOP))
 			continue;
 
-		soc_pcm_hw_free(be_substream);
+		__soc_pcm_hw_free(be, be_substream);
 	}
 
 	return ret;
@@ -1979,7 +2058,7 @@ static int dpcm_fe_dai_hw_params(struct snd_pcm_substream *substream,
 	struct snd_soc_pcm_runtime *fe = asoc_substream_to_rtd(substream);
 	int ret, stream = substream->stream;
 
-	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	snd_soc_dpcm_mutex_lock(fe);
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_FE);
 
 	memcpy(&fe->dpcm[stream].hw_params, params,
@@ -1993,7 +2072,7 @@ static int dpcm_fe_dai_hw_params(struct snd_pcm_substream *substream,
 			params_channels(params), params_format(params));
 
 	/* call hw_params on the frontend */
-	ret = soc_pcm_hw_params(substream, params);
+	ret = __soc_pcm_hw_params(fe, substream, params);
 	if (ret < 0)
 		dpcm_be_dai_hw_free(fe, stream);
 	else
@@ -2001,7 +2080,7 @@ static int dpcm_fe_dai_hw_params(struct snd_pcm_substream *substream,
 
 out:
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_NO);
-	mutex_unlock(&fe->card->mutex);
+	snd_soc_dpcm_mutex_unlock(fe);
 
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s failed (%d)\n", __func__, ret);
@@ -2272,7 +2351,7 @@ int dpcm_be_dai_prepare(struct snd_soc_pcm_runtime *fe, int stream)
 		dev_dbg(be->dev, "ASoC: prepare BE %s\n",
 			be->dai_link->name);
 
-		ret = soc_pcm_prepare(be_substream);
+		ret = __soc_pcm_prepare(be, be_substream);
 		if (ret < 0)
 			break;
 
@@ -2290,7 +2369,7 @@ static int dpcm_fe_dai_prepare(struct snd_pcm_substream *substream)
 	struct snd_soc_pcm_runtime *fe = asoc_substream_to_rtd(substream);
 	int stream = substream->stream, ret = 0;
 
-	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	snd_soc_dpcm_mutex_lock(fe);
 
 	dev_dbg(fe->dev, "ASoC: prepare FE %s\n", fe->dai_link->name);
 
@@ -2309,7 +2388,7 @@ static int dpcm_fe_dai_prepare(struct snd_pcm_substream *substream)
 		goto out;
 
 	/* call prepare on the frontend */
-	ret = soc_pcm_prepare(substream);
+	ret = __soc_pcm_prepare(fe, substream);
 	if (ret < 0)
 		goto out;
 
@@ -2317,7 +2396,7 @@ static int dpcm_fe_dai_prepare(struct snd_pcm_substream *substream)
 
 out:
 	dpcm_set_fe_update_state(fe, stream, SND_SOC_DPCM_UPDATE_NO);
-	mutex_unlock(&fe->card->mutex);
+	snd_soc_dpcm_mutex_unlock(fe);
 
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
@@ -2368,7 +2447,6 @@ 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);
@@ -2437,7 +2515,6 @@ 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);
 	for_each_dpcm_be(fe, stream, dpcm) {
 		struct snd_soc_pcm_runtime *be = dpcm->be;
 
@@ -2449,7 +2526,6 @@ 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);
 
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s() failed (%d)\n", __func__, ret);
@@ -2524,7 +2600,7 @@ int snd_soc_dpcm_runtime_update(struct snd_soc_card *card)
 	struct snd_soc_pcm_runtime *fe;
 	int ret = 0;
 
-	mutex_lock_nested(&card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	mutex_lock_nested(&card->pcm_mutex, card->pcm_subclass);
 	/* shutdown all old paths first */
 	for_each_card_rtds(card, fe) {
 		ret = soc_dpcm_fe_runtime_update(fe, 0);
@@ -2540,7 +2616,7 @@ int snd_soc_dpcm_runtime_update(struct snd_soc_card *card)
 	}
 
 out:
-	mutex_unlock(&card->mutex);
+	mutex_unlock(&card->pcm_mutex);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(snd_soc_dpcm_runtime_update);
@@ -2551,6 +2627,8 @@ static void dpcm_fe_dai_cleanup(struct snd_pcm_substream *fe_substream)
 	struct snd_soc_dpcm *dpcm;
 	int stream = fe_substream->stream;
 
+	snd_soc_dpcm_mutex_assert_held(fe);
+
 	/* mark FE's links ready to prune */
 	for_each_dpcm_be(fe, stream, dpcm)
 		dpcm->state = SND_SOC_DPCM_LINK_STATE_FREE;
@@ -2565,12 +2643,12 @@ static int dpcm_fe_dai_close(struct snd_pcm_substream *fe_substream)
 	struct snd_soc_pcm_runtime *fe = asoc_substream_to_rtd(fe_substream);
 	int ret;
 
-	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	snd_soc_dpcm_mutex_lock(fe);
 	ret = dpcm_fe_dai_shutdown(fe_substream);
 
 	dpcm_fe_dai_cleanup(fe_substream);
 
-	mutex_unlock(&fe->card->mutex);
+	snd_soc_dpcm_mutex_unlock(fe);
 	return ret;
 }
 
@@ -2581,7 +2659,7 @@ static int dpcm_fe_dai_open(struct snd_pcm_substream *fe_substream)
 	int ret;
 	int stream = fe_substream->stream;
 
-	mutex_lock_nested(&fe->card->mutex, SND_SOC_CARD_CLASS_RUNTIME);
+	snd_soc_dpcm_mutex_lock(fe);
 	fe->dpcm[stream].runtime = fe_substream->runtime;
 
 	ret = dpcm_path_get(fe, stream, &list);
@@ -2598,7 +2676,7 @@ static int dpcm_fe_dai_open(struct snd_pcm_substream *fe_substream)
 	dpcm_clear_pending_state(fe, stream);
 	dpcm_path_put(&list);
 open_end:
-	mutex_unlock(&fe->card->mutex);
+	snd_soc_dpcm_mutex_unlock(fe);
 	return ret;
 }
 
@@ -2859,10 +2937,8 @@ 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);
 	for_each_dpcm_fe(be, stream, dpcm) {
 
 		if (dpcm->fe == fe)
@@ -2876,7 +2952,6 @@ static int snd_soc_dpcm_check_state(struct snd_soc_pcm_runtime *fe,
 			}
 		}
 	}
-	spin_unlock_irqrestore(&fe->card->dpcm_lock, flags);
 
 	/* it's safe to do this BE DAI */
 	return ret;
-- 
2.31.1


[-- Attachment #4: 0003-ASoC-DPCM-Take-a-stream-lock-at-BE-trigger-operation.patch --]
[-- Type: application/octet-stream, Size: 4502 bytes --]

From 3c41e986a386fd157dd8270d0ce3e402df1bfd0e Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Fri, 15 Oct 2021 17:17:55 +0200
Subject: [PATCH 3/3] ASoC: DPCM: Take a stream lock at BE trigger operation

For avoiding the race among concurrent accesses to BEs.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/soc/soc-pcm.c | 46 ++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index 5bd4f953359a..edfda2e30c7f 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -46,12 +46,18 @@ static inline void snd_soc_dpcm_stream_lock_irq(struct snd_soc_pcm_runtime *rtd,
 	snd_pcm_stream_lock_irq(snd_soc_dpcm_get_substream(rtd, stream));
 }
 
+#define snd_soc_dpcm_stream_lock_irqsave(rtd, stream, flags) \
+	snd_pcm_stream_lock_irqsave(snd_soc_dpcm_get_substream(rtd, stream), flags)
+
 static inline void snd_soc_dpcm_stream_unlock_irq(struct snd_soc_pcm_runtime *rtd,
 						  int stream)
 {
 	snd_pcm_stream_unlock_irq(snd_soc_dpcm_get_substream(rtd, stream));
 }
 
+#define snd_soc_dpcm_stream_unlock_irqrestore(rtd, stream, flags) \
+	snd_pcm_stream_unlock_irqrestore(snd_soc_dpcm_get_substream(rtd, stream), flags)
+
 #define DPCM_MAX_BE_USERS	8
 
 static inline const char *soc_cpu_dai_name(struct snd_soc_pcm_runtime *rtd)
@@ -2093,6 +2099,7 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 {
 	struct snd_soc_pcm_runtime *be;
 	struct snd_soc_dpcm *dpcm;
+	unsigned long flags;
 	int ret = 0;
 
 	for_each_dpcm_be(fe, stream, dpcm) {
@@ -2101,9 +2108,11 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 		be = dpcm->be;
 		be_substream = snd_soc_dpcm_get_substream(be, stream);
 
+		snd_soc_dpcm_stream_lock_irqsave(be, stream, flags);
+
 		/* is this op for this BE ? */
 		if (!snd_soc_dpcm_be_can_update(fe, be, stream))
-			continue;
+			goto next;
 
 		dev_dbg(be->dev, "ASoC: trigger BE %s cmd %d\n",
 			be->dai_link->name, cmd);
@@ -2113,77 +2122,80 @@ int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream,
 			if ((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;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
 		case SNDRV_PCM_TRIGGER_RESUME:
 			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_SUSPEND))
-				continue;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
 		case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
-				continue;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_START;
 			break;
 		case SNDRV_PCM_TRIGGER_STOP:
 			if ((be->dpcm[stream].state != SND_SOC_DPCM_STATE_START) &&
 			    (be->dpcm[stream].state != SND_SOC_DPCM_STATE_PAUSED))
-				continue;
+				goto next;
 
 			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
-				continue;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_STOP;
 			break;
 		case SNDRV_PCM_TRIGGER_SUSPEND:
 			if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
-				continue;
+				goto next;
 
 			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
-				continue;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_SUSPEND;
 			break;
 		case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 			if (be->dpcm[stream].state != SND_SOC_DPCM_STATE_START)
-				continue;
+				goto next;
 
 			if (!snd_soc_dpcm_can_be_free_stop(fe, be, stream))
-				continue;
+				goto next;
 
 			ret = soc_pcm_trigger(be_substream, cmd);
 			if (ret)
-				goto end;
+				goto next;
 
 			be->dpcm[stream].state = SND_SOC_DPCM_STATE_PAUSED;
 			break;
 		}
+	next:
+		snd_soc_dpcm_stream_unlock_irqrestore(be, stream, flags);
+		if (ret)
+			break;
 	}
-end:
 	if (ret < 0)
 		dev_err(fe->dev, "ASoC: %s() failed at %s (%d)\n",
 			__func__, be->dai_link->name, ret);
-- 
2.31.1