restore AST_LIST_HEAD_INIT (with no users in the tree right now)

update ast_mutex_init to allow mutexes that are all zero bytes to be initialized (in the case of a dynamically-allocated structure containing a mutex)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@29727 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/linkedlists.h

@@ -359,6 +359,19 @@ struct {								\
  */
 #define AST_LIST_TRAVERSE_SAFE_END  }
 
+/*!
+  \brief Initializes a list head structure.
+  \param head This is a pointer to the list head structure
+
+  This macro initializes a list head structure by setting the head
+  entry to \a NULL (empty list) and recreating the embedded lock.
+*/
+#define AST_LIST_HEAD_INIT(head) {					\
+	(head)->first = NULL;						\
+	(head)->last = NULL;						\
+	ast_mutex_init(&(head)->lock);					\
+}
+
 /*!
   \brief Destroys a list head structure.
   \param head This is a pointer to the list head structure

include/asterisk/lock.h

@@ -149,6 +149,13 @@ typedef struct ast_mutex_info ast_mutex_t;
 
 typedef pthread_cond_t ast_cond_t;
 
+static pthread_mutex_t empty_mutex;
+
+static void __attribute__((constructor)) init_empty_mutex(void)
+{
+	memset(&empty_mutex, 0, sizeof(empty_mutex));
+}
+
 static inline int __ast_pthread_mutex_init_attr(const char *filename, int lineno, const char *func,
 						const char *mutex_name, ast_mutex_t *t,
 						pthread_mutexattr_t *attr) 
@@ -157,14 +164,16 @@ static inline int __ast_pthread_mutex_init_attr(const char *filename, int lineno
 	int canlog = strcmp(filename, "logger.c");
 
 	if ((t->mutex) != ((pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER)) {
-		__ast_mutex_logger("%s line %d (%s): Error: mutex '%s' is already initialized.\n",
-				   filename, lineno, func, mutex_name);
-		__ast_mutex_logger("%s line %d (%s): Error: previously initialization of mutex '%s'.\n",
-				   t->file[0], t->lineno[0], t->func[0], mutex_name);
+		if ((t->mutex) != (empty_mutex)) {
+			__ast_mutex_logger("%s line %d (%s): Error: mutex '%s' is already initialized.\n",
+					   filename, lineno, func, mutex_name);
+			__ast_mutex_logger("%s line %d (%s): Error: previously initialization of mutex '%s'.\n",
+					   t->file[0], t->lineno[0], t->func[0], mutex_name);
 #ifdef THREAD_CRASH
-		DO_THREAD_CRASH;
+			DO_THREAD_CRASH;
 #endif
-		return 0;
+			return 0;
+		}
 	}
 #endif