ALSA: pcm: Use snd_pcm_stop_xrun() for xrun injection

Basically the xrun injection routine can simply call the standard
helper snd_pcm_stop_xrun(), but with one exception: it may be called
even when the stream is closed.

Make snd_pcm_stop_xrun() more robust and check the NULL runtime state,
and simplify xrun injection code by calling it.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/pcm.c

@@ -492,13 +492,8 @@ static void snd_pcm_xrun_injection_write(struct snd_info_entry *entry,
 					 struct snd_info_buffer *buffer)
 {
 	struct snd_pcm_substream *substream = entry->private_data;
-	struct snd_pcm_runtime *runtime;
 
-	snd_pcm_stream_lock_irq(substream);
-	runtime = substream->runtime;
-	if (runtime && runtime->status->state == SNDRV_PCM_STATE_RUNNING)
-		__snd_pcm_xrun(substream);
-	snd_pcm_stream_unlock_irq(substream);
+	snd_pcm_stop_xrun(substream);
 }
 
 static void snd_pcm_xrun_debug_read(struct snd_info_entry *entry,

sound/core/pcm_native.c

@@ -1339,7 +1339,7 @@ int snd_pcm_stop_xrun(struct snd_pcm_substream *substream)
 	unsigned long flags;
 
 	snd_pcm_stream_lock_irqsave(substream, flags);
-	if (snd_pcm_running(substream))
+	if (substream->runtime && snd_pcm_running(substream))
 		__snd_pcm_xrun(substream);
 	snd_pcm_stream_unlock_irqrestore(substream, flags);
 	return 0;