TT#99503 fix possible T.38 gateway deadlock

closes #1100

Change-Id: Ifd4be1ca5d4f343a805be31d39abdb73011ec6c4
(cherry picked from commit 0c581e59a1)

daemon/t38.c

@@ -283,12 +283,17 @@ static void t38_pcm_player(struct media_player *mp) {
 
 	ilog(LOG_DEBUG, "Generated %i T.38 PCM samples", num);
 
-	// this reschedules our player as well
-	media_player_add_packet(tg->pcm_player, (char *) smp, num * 2, num * 1000000 / 8000, tg->pts);
-
+	// release gateway lock as the media player may trigger a lock on the SSRC objects
+	// and this is the wrong lock order
+	struct media_player *pcm_player = media_player_get(tg->pcm_player);
+	unsigned long long pts = tg->pts;
 	tg->pts += num;
 
 	mutex_unlock(&tg->lock);
+
+	// this reschedules our player as well
+	media_player_add_packet(pcm_player, (char *) smp, num * 2, num * 1000000 / 8000, pts);
+	media_player_put(&pcm_player);
 }
 
 

include/media_player.h

@@ -60,11 +60,20 @@ INLINE void media_player_put(struct media_player **mp) {
 	obj_put(&(*mp)->tt_obj);
 	*mp = NULL;
 }
+INLINE struct media_player *media_player_get(struct media_player *mp) {
+	if (!mp)
+		return NULL;
+	obj_hold(&mp->tt_obj);
+	return mp;
+}
 
 #else
 
 INLINE void media_player_put(struct media_player **mp) {
 }
+INLINE struct media_player *media_player_get(struct media_player *mp) {
+	return NULL;
+}
 
 #endif