Add some comments

src/ucore_logging.c

@@ -12,10 +12,12 @@
 struct uc_log_destination {
     SLIST_ENTRY(uc_log_destination) entry;
     enum UC_LOG_DESTINATION dest_type;
+    //log level for this destination
     int log_level;
+    //Whether to log the source file name and line number 
     int log_location;
     union {
-        //for syslog
+        //for syslog openlog()
         struct {
             char *ident; 
             int facility; 
@@ -28,6 +30,7 @@ struct uc_log_destination {
     } type;
 };
 
+/* Helper struct for arguments to our main logging function */
 struct uc_log_args {
     struct uc_log_destination *dest;
     const struct uc_log_module *module;
@@ -51,6 +54,8 @@ static const struct uc_log_module unknown_module = {
 };
 
 
+//All destinations. The log_lock must be held while accessing
+//this list an anything contained within it.
 static SLIST_HEAD(, uc_log_destination) destinations;
 
 inline const char *uc_ll_2_str(enum UC_LOG_LEVEL l)
@@ -180,6 +185,7 @@ void uc_log_add_destination(struct uc_log_destination *dest)
     pthread_mutex_unlock(&log_lock);
 }
 
+//hold log_lock while calling this.
 static inline void uc_log_remove_dest_unlocked(struct uc_log_destination *dest)
 {
     struct uc_log_destination *it;
@@ -212,7 +218,7 @@ void uc_log_delete_destination(struct uc_log_destination *dest)
 
     pthread_mutex_lock(&log_lock);
 
-    //remove it
+    //remove it, it's ok if the destination is already removed
     uc_log_remove_dest_unlocked(dest);
 
     //clean up, according to the type