ALSA: pcm: Unify snd_pcm_group initialization

There are multiple open codes that initialize the same object.
Create a common helper function instead.

Also, use kzalloc() to be safer at creating a group object, and move
the initialization out of the critical section.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm.c

@@ -753,9 +753,7 @@ int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)
 			}
 		}
 		substream->group = &substream->self_group;
-		spin_lock_init(&substream->self_group.lock);
-		mutex_init(&substream->self_group.mutex);
-		INIT_LIST_HEAD(&substream->self_group.substreams);
+		snd_pcm_group_init(&substream->self_group);
 		list_add_tail(&substream->link_list, &substream->self_group.substreams);
 		atomic_set(&substream->mmap_count, 0);
 		prev = substream;

sound/core/pcm_local.h

@@ -66,5 +66,6 @@ static inline void snd_pcm_timer_done(struct snd_pcm_substream *substream) {}
 #endif
 
 void __snd_pcm_xrun(struct snd_pcm_substream *substream);
+void snd_pcm_group_init(struct snd_pcm_group *group);
 
 #endif	/* __SOUND_CORE_PCM_LOCAL_H */

sound/core/pcm_native.c

@@ -100,6 +100,13 @@ static inline void down_write_nonfifo(struct rw_semaphore *lock)
 		msleep(1);
 }
 
+void snd_pcm_group_init(struct snd_pcm_group *group)
+{
+	spin_lock_init(&group->lock);
+	mutex_init(&group->mutex);
+	INIT_LIST_HEAD(&group->substreams);
+}
+
 #define PCM_LOCK_DEFAULT	0
 #define PCM_LOCK_IRQ	1
 #define PCM_LOCK_IRQSAVE	2
@@ -1969,11 +1976,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
 	}
 	pcm_file = f.file->private_data;
 	substream1 = pcm_file->substream;
-	group = kmalloc(sizeof(*group), GFP_KERNEL);
+	group = kzalloc(sizeof(*group), GFP_KERNEL);
 	if (!group) {
 		res = -ENOMEM;
 		goto _nolock;
 	}
+	snd_pcm_group_init(group);
 	down_write_nonfifo(&snd_pcm_link_rwsem);
 	write_lock_irq(&snd_pcm_link_rwlock);
 	if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN ||
@@ -1989,9 +1997,6 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
 	if (!snd_pcm_stream_linked(substream)) {
 		substream->group = group;
 		group = NULL;
-		spin_lock_init(&substream->group->lock);
-		mutex_init(&substream->group->mutex);
-		INIT_LIST_HEAD(&substream->group->substreams);
 		list_add_tail(&substream->link_list, &substream->group->substreams);
 		substream->group->count = 1;
 	}