[ALSA] pcsp: locking fix

pcsp: locking fix.

Signed-off-by: Stas Sergeev <stsp@aknet.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/drivers/pcsp/pcsp_lib.c b/sound/drivers/pcsp/pcsp_lib.c
index a302756..54253e9 100644
--- a/sound/drivers/pcsp/pcsp_lib.c
+++ b/sound/drivers/pcsp/pcsp_lib.c
@@ -305,7 +305,9 @@
 		return -EBUSY;
 	}
 	runtime->hw = snd_pcsp_playback;
+	spin_lock_irq(&chip->substream_lock);
 	chip->playback_substream = substream;
+	spin_unlock_irq(&chip->substream_lock);
 	return 0;
 }