Read lock the contexts to maintain the locking order when we are notified that the state of a device has changed.

(closes issue #13839)
Reported by: mcallist


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@169867 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/pbx.c

@@ -2027,6 +2027,7 @@ void ast_hint_state_changed(const char *device)
 {
 	struct ast_hint *hint;
 
+	ast_rdlock_contexts();
 	AST_LIST_LOCK(&hints);
 
 	AST_LIST_TRAVERSE(&hints, hint, list) {
@@ -2064,6 +2065,7 @@ void ast_hint_state_changed(const char *device)
 	}
 
 	AST_LIST_UNLOCK(&hints);
+	ast_unlock_contexts();
 }
 
 /*! \brief  ast_extension_state_add: Add watcher for extension states */