[PATCH] ASoC: soc-core: add snd_soc_find_dai_with_mutex()

* [PATCH] ASoC: soc-core: add snd_soc_find_dai_with_mutex()
@ 2020-08-26 23:55 Kuninori Morimoto
  2020-08-27 13:56 ` Mark Brown
  0 siblings, 1 reply; 4+ messages in thread
From: Kuninori Morimoto @ 2020-08-26 23:55 UTC (permalink / raw)
  To: Mark Brown, Pierre-Louis Bossart; +Cc: Linux-ALSA


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

commit 25612477d20b52 ("ASoC: soc-dai: set dai_link dpcm_ flags with a helper")
added snd_soc_dai_link_set_capabilities().
But it is using snd_soc_find_dai() (A) which is required client_mutex (B).
And client_mutex is soc-core.c local.

	struct snd_soc_dai *snd_soc_find_dai(xxx)
	{
		...
(B)		lockdep_assert_held(&client_mutex);
		...
	}

	void snd_soc_dai_link_set_capabilities(xxx)
	{
		...
		for_each_pcm_streams(direction) {
			...
			for_each_link_cpus(dai_link, i, cpu) {
(A)				dai = snd_soc_find_dai(cpu);
				...
			}
			...
			for_each_link_codecs(dai_link, i, codec) {
(A)				dai = snd_soc_find_dai(codec);
				...
			}
		}
		...
	}

Because of these background, we will get WARNING if .config has CONFIG_LOCKDEP.

	WARNING: CPU: 2 PID: 53 at sound/soc/soc-core.c:814 snd_soc_find_dai+0xf8/0x100
	CPU: 2 PID: 53 Comm: kworker/2:1 Not tainted 5.7.0-rc1+ #328
	Hardware name: Renesas H3ULCB Kingfisher board based on r8a77951 (DT)
	Workqueue: events deferred_probe_work_func
	pstate: 60000005 (nZCv daif -PAN -UAO)
	pc : snd_soc_find_dai+0xf8/0x100
	lr : snd_soc_find_dai+0xf4/0x100
	...
	Call trace:
	 snd_soc_find_dai+0xf8/0x100
	 snd_soc_dai_link_set_capabilities+0xa0/0x16c
	 graph_dai_link_of_dpcm+0x390/0x3c0
	 graph_for_each_link+0x134/0x200
	 graph_probe+0x144/0x230
	 platform_drv_probe+0x5c/0xb0
	 really_probe+0xe4/0x430
	 driver_probe_device+0x60/0xf4

snd_soc_find_dai() will be used from (X) CPU/Codec/Platform driver with
mutex lock, and (Y) Card driver without mutex lock.
This snd_soc_dai_link_set_capabilities() is for Card driver,
this means called without mutex.
This patch adds snd_soc_find_dai_with_mutex() to solve it.

Fixes: 25612477d20b52 ("ASoC: soc-dai: set dai_link dpcm_ flags with a helper")
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
---

This patch was originally "ASoC: soc-core: move snd_soc_dai_link_set_capabilities() to soc-core.c".
This is for asoc/for-5.9 branch

 include/sound/soc.h  |  2 ++
 sound/soc/soc-core.c | 13 +++++++++++++
 sound/soc/soc-dai.c  |  4 ++--
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 5e3919ffb00c..4176071f61bf 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1361,6 +1361,8 @@ void snd_soc_unregister_dai(struct snd_soc_dai *dai);
 
 struct snd_soc_dai *snd_soc_find_dai(
 	const struct snd_soc_dai_link_component *dlc);
+struct snd_soc_dai *snd_soc_find_dai_with_mutex(
+	const struct snd_soc_dai_link_component *dlc);
 
 #include <sound/soc-dai.h>
 
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 2fe1b2ec7c8f..fe11856d7a63 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -834,6 +834,19 @@ struct snd_soc_dai *snd_soc_find_dai(
 }
 EXPORT_SYMBOL_GPL(snd_soc_find_dai);
 
+struct snd_soc_dai *snd_soc_find_dai_with_mutex(
+	const struct snd_soc_dai_link_component *dlc)
+{
+	struct snd_soc_dai *dai;
+
+	mutex_lock(&client_mutex);
+	dai = snd_soc_find_dai(dlc);
+	mutex_unlock(&client_mutex);
+
+	return dai;
+}
+EXPORT_SYMBOL_GPL(snd_soc_find_dai_with_mutex);
+
 static int soc_dai_link_sanity_check(struct snd_soc_card *card,
 				     struct snd_soc_dai_link *link)
 {
diff --git a/sound/soc/soc-dai.c b/sound/soc/soc-dai.c
index 91a2551e4cef..0dbd312aad08 100644
--- a/sound/soc/soc-dai.c
+++ b/sound/soc/soc-dai.c
@@ -412,14 +412,14 @@ void snd_soc_dai_link_set_capabilities(struct snd_soc_dai_link *dai_link)
 		supported_codec = false;
 
 		for_each_link_cpus(dai_link, i, cpu) {
-			dai = snd_soc_find_dai(cpu);
+			dai = snd_soc_find_dai_with_mutex(cpu);
 			if (dai && snd_soc_dai_stream_valid(dai, direction)) {
 				supported_cpu = true;
 				break;
 			}
 		}
 		for_each_link_codecs(dai_link, i, codec) {
-			dai = snd_soc_find_dai(codec);
+			dai = snd_soc_find_dai_with_mutex(codec);
 			if (dai && snd_soc_dai_stream_valid(dai, direction)) {
 				supported_codec = true;
 				break;
-- 
2.25.1


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