Index: asterisk-1.6.2.18/main/channel.c
===================================================================
--- asterisk-1.6.2.18.orig/main/channel.c	2011-06-03 14:35:25.000000000 +0100
+++ asterisk-1.6.2.18/main/channel.c	2011-06-03 15:21:42.000000000 +0100
@@ -5042,7 +5042,13 @@
 			clonechan->hangupcause,
 			ast_cause2str(clonechan->hangupcause)
 			);
+		/*
+		 * Cannot hold a channel lock already when calling ast_channel_free() as it walks the
+		 * channel list and needs the &channels lock. Unlock and re-lock to avoid deadlock
+		 */
+		ast_channel_unlock(original);
 		ast_channel_free(clonechan);
+		ast_channel_lock(original);
 	} else {
 		ast_debug(1, "Released clone lock on '%s'\n", clonechan->name);
 		ast_set_flag(clonechan, AST_FLAG_ZOMBIE);