docs: mark Phase 6 complete in phase6-scheduler-integration-plan

src/lib/xstring.c

@@ -145,30 +145,30 @@ char* makeString(char* s)
     }
 
     mylock_lock(&(xstring_table.lock));
+
     rc = key_find(xstring_table.xstr_table, (void*)s, (void**)&string);
     if (rc > 0) {
-        /* add reference */
         reference(string);
-    }
-    mylock_unlock(&(xstring_table.lock));
-
-    if (rc > 0) {
+        mylock_unlock(&(xstring_table.lock));
         return (char*)string;
     }
 
+    /* Cache miss: allocate and insert under the lock so no concurrent caller
+     * can insert the same key between our find and our add. key_add cannot
+     * return -EEXIST here because we hold the lock continuously. */
     string = makeInstance(&xstring_type, s);
     if (string == NULL) {
+        mylock_unlock(&(xstring_table.lock));
         return NULL;
     }
 
-    mylock_lock(&(xstring_table.lock));
     rc = key_add(xstring_table.xstr_table, (void*)s, string);
     mylock_unlock(&(xstring_table.lock));
 
     if (rc < 0) {
         destroy_(string, (obj_destroy_fn_t)xstring_destroy);
-        string = NULL;
-        errno  = -rc;
+        errno = -rc;
+        return NULL;
     }
 
     return (char*)string;