Reworked deadlock avoidance in __ast_read. Restored audio to

callback agents.

(closes issue #11071, reported by callguy, patched by me, tested by callguy and Ted Brown)



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@88826 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -2181,14 +2181,20 @@ static void ast_read_generator_actions(struct ast_channel *chan, struct ast_fram
 static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
 {
 	struct ast_frame *f = NULL;	/* the return value */
-	struct ast_channel *base = NULL;
 	int blah;
 	int prestate;
+	int count = 0;
 
 	/* this function is very long so make sure there is only one return
-	 * point at the end (there is only one exception to this).
+	 * point at the end (there are only two exceptions to this).
 	 */
-	ast_channel_lock(chan);
+	while(ast_channel_trylock(chan)) {
+		if(count++ > 10) 
+			/*cannot goto done since the channel is not locked*/
+			return &ast_null_frame;
+		usleep(1);
+	}
+
 	if (chan->masq) {
 		if (ast_do_masquerade(chan))
 			ast_log(LOG_WARNING, "Failed to perform masquerade\n");
@@ -2205,23 +2211,6 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
 	}
 	prestate = chan->_state;
 
-	/* Check if there's an underlying channel */
-	if (chan->tech->get_base_channel && (base = chan->tech->get_base_channel(chan)) != chan) {
-		int count = 0;
-		while (!base || ast_mutex_trylock(&base->lock)) {
-			if (count++ > 10) {
-				f = &ast_null_frame;
-				goto done;
-			}
-			ast_mutex_unlock(&chan->lock);
-			usleep(1);
-			ast_mutex_lock(&chan->lock);
-			base = chan->tech->get_base_channel(chan);
-		}
-		ast_mutex_unlock(&chan->lock);
-		chan = base;
-	}
-
 	if (!ast_test_flag(chan, AST_FLAG_DEFER_DTMF | AST_FLAG_EMULATE_DTMF | AST_FLAG_IN_DTMF) && 
 	    !ast_strlen_zero(chan->dtmfq) && 
 		(ast_tvzero(chan->dtmf_tv) || ast_tvdiff_ms(ast_tvnow(), chan->dtmf_tv) > AST_MIN_DTMF_GAP) ) {