Protect against creating two default COs from two threads.

mixxxdj · Aug 20, 2021 · bb389e9 · bb389e9
1 parent f231655
commit bb389e9
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/src/control/control.cpp b/src/control/control.cpp
@@ -186,8 +186,15 @@ QSharedPointer<ControlDoublePrivate> ControlDoublePrivate::getControl(
 QSharedPointer<ControlDoublePrivate> ControlDoublePrivate::getDefaultControl() {
     auto defaultCO = QSharedPointer<ControlDoublePrivate>(s_defaultCO);
     if (!defaultCO) {
-        defaultCO = QSharedPointer<ControlDoublePrivate>(new ControlDoublePrivateConst());
-        s_defaultCO = defaultCO;
+        // Try again with the mutex locked to protect against creating two
+        // ControlDoublePrivateConst objects. Access to s_defaultCO itself is
+        // thread save.
+        MMutexLocker locker(&s_qCOHashMutex);
+        defaultCO = QSharedPointer<ControlDoublePrivate>(s_defaultCO);
+        if (!defaultCO) {
+            defaultCO = QSharedPointer<ControlDoublePrivate>(new ControlDoublePrivateConst());
+            s_defaultCO = defaultCO;
+        }
     }
     return defaultCO;
 }