--- ../clean/asterisk-1.6.2.17-rc2/channels/chan_sip.c	2011-01-12 23:05:02.000000000 +0200
+++ channels/chan_sip.c	2011-02-17 14:16:09.000000000 +0200
@@ -7154,6 +7154,12 @@
 
 	sip_pvt_lock(p);
 	fr = sip_rtp_read(ast, p, &faxdetected);
+
+	if (((fr == &ast_null_frame) && p->rtp && !ast_rtp_get_bridged(p->rtp)) || (!p->rtp)) {
+		sip_pvt_unlock(p);
+		return fr;
+	}
+
 	p->lastrtprx = time(NULL);
 
 	/* If we detect a CNG tone and fax detection is enabled then send us off to the fax extension */
@@ -22686,14 +22692,10 @@
 		     (t > dialog->lastrtprx + ast_rtp_get_rtpholdtimeout(dialog->rtp)))) {
 			/* Needs a hangup */
 			if (ast_rtp_get_rtptimeout(dialog->rtp)) {
-				while (dialog->owner && ast_channel_trylock(dialog->owner)) {
-					sip_pvt_unlock(dialog);
-					usleep(1);
-					sip_pvt_lock(dialog);
-				}
-				if (!dialog->owner) {
-					return; /* channel hangup can occur during deadlock avoidance. */
-				}
+				/* Don't block the monitor thread.  This function is called often enough
+				 * that we can wait for the next time around. */
+				if ((!dialog->owner) || (dialog->owner && ast_channel_trylock(dialog->owner)))
+					return;
 				ast_log(LOG_NOTICE, "Disconnecting call '%s' for lack of RTP activity in %ld seconds\n",
 					dialog->owner->name, (long) (t - dialog->lastrtprx));
 				/* Issue a softhangup */