Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 107959)
+++ channels/chan_sip.c	(working copy)
@@ -2250,6 +2250,7 @@
 }
 
 #define sip_pvt_lock(x) ast_mutex_lock(&x->pvt_lock)
+#define sip_pvt_trylock(x) ast_mutex_trylock(&x->pvt_lock)
 #define sip_pvt_unlock(x) ast_mutex_unlock(&x->pvt_lock)
 
 /*!
@@ -18332,7 +18333,13 @@
 		   get back to this point every millisecond or less)
 		*/
 		for (dialog = dialoglist; dialog; dialog = dialog->next) {
-			sip_pvt_lock(dialog);
+			if (sip_pvt_trylock(dialog)) {
+				dialoglist_unlock();
+				usleep(1);
+				dialoglist_lock();
+				goto restartsearch;
+			}
+
 			/* Check RTP timeouts and kill calls if we have a timeout set and do not get RTP */
 			check_rtp_timeout(dialog, t);
 			/* If we have sessions that needs to be destroyed, do it now */