[PATCH v3 1/5] ALSA: hda: Serialize codec probe and remove on the same bus

[Cen Zhang]

The probe and remove of different codecs on one HD-audio bus can run at
the same time, for example when two codecs are bound and unbound through
sysfs. A codec probe on a registered card calls snd_card_register(),
which walks card->devices in snd_device_register_all(), while the remove
of another codec frees its PCMs and deletes them from the same list.
The list has no lock of its own.

Add a mutex to struct hdac_bus and hold it in hda_codec_driver_probe()
and hda_codec_driver_remove(). The ASoC ext_ops paths are unchanged.

Fixes: bcd96557bd0a ("ALSA: hda - Build PCMs and controls at codec driver probe")
Suggested-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Cen Zhang <zzzccc427@xxxxxxxxx>
---
 include/sound/hdaudio.h | 1 +
 sound/hda/common/bind.c | 7 +++++++
 sound/hda/core/bus.c    | 1 +
 3 files changed, 9 insertions(+)

diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
index 04fd4794bcee..066d2fef3986 100644
--- a/include/sound/hdaudio.h
+++ b/include/sound/hdaudio.h
@@ -367,6 +367,7 @@ struct hdac_bus {
 	spinlock_t reg_lock;
 	struct mutex cmd_mutex;
 	struct mutex lock;
+	struct mutex codec_bind_lock;	/* codec driver probe and remove */
 
 	/* DRM component interface */
 	struct drm_audio_component *audio_component;
diff --git a/sound/hda/common/bind.c b/sound/hda/common/bind.c
index 957feace0f58..abbb3b64ec09 100644
--- a/sound/hda/common/bind.c
+++ b/sound/hda/common/bind.c
@@ -104,6 +104,12 @@ static int hda_codec_driver_probe(struct device *dev)
 	if (WARN_ON(!codec->preset))
 		return -EINVAL;
 
+	/*
+	 * snd_card_register() below walks the device list of the card, which
+	 * the removal of another codec changes when it frees its PCMs.
+	 */
+	guard(mutex)(&codec->bus->core.codec_bind_lock);
+
 	err = snd_hda_codec_set_name(codec, codec->preset->name);
 	if (err < 0)
 		goto error;
@@ -171,6 +177,7 @@ static int hda_codec_driver_remove(struct device *dev)
 		return codec->bus->core.ext_ops->hdev_detach(&codec->core);
 	}
 
+	guard(mutex)(&codec->bus->core.codec_bind_lock);
 	snd_hda_codec_disconnect_pcms(codec);
 	snd_hda_jack_tbl_disconnect(codec);
 	snd_refcount_sync(&codec->pcm_ref);
diff --git a/sound/hda/core/bus.c b/sound/hda/core/bus.c
index 02462bd035e7..304110c9a6a7 100644
--- a/sound/hda/core/bus.c
+++ b/sound/hda/core/bus.c
@@ -44,6 +44,7 @@ int snd_hdac_bus_init(struct hdac_bus *bus, struct device *dev,
 	spin_lock_init(&bus->reg_lock);
 	mutex_init(&bus->cmd_mutex);
 	mutex_init(&bus->lock);
+	mutex_init(&bus->codec_bind_lock);
 	INIT_LIST_HEAD(&bus->hlink_list);
 	init_waitqueue_head(&bus->rirb_wq);
 	bus->irq = -1;
-- 
2.43.0