More logging docs

src/ucore_logging.h

@@ -1,6 +1,12 @@
 #ifndef UCORE_LOGGING_H_
 #define UCORE_LOGGING_H_
 
+/** Logging functions. 
+ * All logging functions except uc_log_init are thread safe,
+ * so logging can be performed from any thread after the logging 
+ * system have been initialized.
+ */
+
 /** The log levels defined by ucore logging*/
 enum UC_LOG_LEVEL {
     UC_LL_NONE    = 0,
@@ -139,6 +145,9 @@ void uc_logf(int log_level, int module, const char *file, int line, const char *
 #endif
 
 /** Main macro that should be used for logging.
+ * 
+ *  For log messages with UC_LL_DEBUG, the UC_DEBUGF() macro can be used,
+ *  UC_DEBUGF will only be compiled in if the DEBUG macro is defined
  *
  * @lvl log level of this log message
  * @mod module id of this log messagex.