3 files changed, 18 insertions, 9 deletions
diff --git a/backends/mutex/mutex.h b/backends/mutex/mutex.h
index d8647bae13..ddf27d5932 100644
--- a/backends/mutex/mutex.h
+++ b/backends/mutex/mutex.h
@@ -29,6 +29,10 @@
 #include "common/system.h"
 #include "common/noncopyable.h"
 
+/**
+ * Abstract class for mutex manager. Subclasses
+ * implement the real functionality.
+ */
 class MutexManager : Common::NonCopyable {
 public:
 	virtual ~MutexManager() {}
@@ -39,5 +43,4 @@ public:
 	virtual void deleteMutex(OSystem::MutexRef mutex) = 0;
 };
 
-
 #endif
diff --git a/backends/mutex/null/null-mutex.h b/backends/mutex/null/null-mutex.h
index ddfe23bdee..54b8f5ce96 100644
--- a/backends/mutex/null/null-mutex.h
+++ b/backends/mutex/null/null-mutex.h
@@ -28,12 +28,15 @@
 
 #include "backends/mutex/mutex.h"
 
+/**
+ * Null mutex manager
+ */
 class NullMutexManager : MutexManager {
 public:
-	OSystem::MutexRef createMutex() { return OSystem::MutexRef(); }
-	void lockMutex(OSystem::MutexRef mutex) {}
-	void unlockMutex(OSystem::MutexRef mutex) {}
-	void deleteMutex(OSystem::MutexRef mutex) {}
+	virtual OSystem::MutexRef createMutex() { return OSystem::MutexRef(); }
+	virtual void lockMutex(OSystem::MutexRef mutex) {}
+	virtual void unlockMutex(OSystem::MutexRef mutex) {}
+	virtual void deleteMutex(OSystem::MutexRef mutex) {}
 };
 
 #endif
diff --git a/backends/mutex/sdl/sdl-mutex.h b/backends/mutex/sdl/sdl-mutex.h
index a929ea495f..88a19d398a 100644
--- a/backends/mutex/sdl/sdl-mutex.h
+++ b/backends/mutex/sdl/sdl-mutex.h
@@ -28,12 +28,15 @@
 
 #include "backends/mutex/mutex.h"
 
+/**
+ * SDL mutex manager
+ */
 class SdlMutexManager : public MutexManager {
 public:
-	OSystem::MutexRef createMutex();
-	void lockMutex(OSystem::MutexRef mutex);
-	void unlockMutex(OSystem::MutexRef mutex);
-	void deleteMutex(OSystem::MutexRef mutex);
+	virtual OSystem::MutexRef createMutex();
+	virtual void lockMutex(OSystem::MutexRef mutex);
+	virtual void unlockMutex(OSystem::MutexRef mutex);
+	virtual void deleteMutex(OSystem::MutexRef mutex);
 };