From Mathias Froehlich, added support for using OpenThreads::Atomic for thread safe ref/unref.

include/osg/Referenced

@@ -30,6 +30,10 @@
 #include <OpenThreads/Mutex>
 #endif
 
+#include <OpenThreads/Atomic>
+#if !defined(_OPENTHREADS_ATOMIC_USE_MUTEX)
+# define _OSG_REFERENCED_USE_ATOMIC_OPERATIONS
+#endif
 
 namespace osg {
 
@@ -57,10 +61,19 @@ class OSG_EXPORT Referenced
         virtual void setThreadSafeRefUnref(bool threadSafe);
 
         /** Get whether a mutex is used to ensure ref() and unref() are thread safe.*/
+
+#if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
+        bool getThreadSafeRefUnref() const { return true; }
+#else
         bool getThreadSafeRefUnref() const { return _refMutex!=0; }
+#endif
 
         /** Get the mutex used to ensure thread safety of ref()/unref(). */
+#if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
+        OpenThreads::Mutex* getRefMutex() const { return 0; }
+#else
         OpenThreads::Mutex* getRefMutex() const { return _refMutex; }
+#endif
 
         /** Increment the reference count by one, indicating that 
             this object has another pointer which is referencing it.*/
@@ -112,17 +125,28 @@ class OSG_EXPORT Referenced
         virtual ~Referenced();
         
         void deleteUsingDeleteHandler() const;
+
+#if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
+        struct ObserverSetData;
+
+        OpenThreads::AtomicPtr<ObserverSetData> _observerSetDataPtr;
+
+        mutable OpenThreads::Atomic     _refCount;
+#else
         
         mutable OpenThreads::Mutex*     _refMutex;
 
         mutable int                     _refCount;
         
-        void*                          _observers;
-        
+        void*                           _observers;
+#endif
 };
 
 inline void Referenced::ref() const
 {
+#if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
+    ++_refCount;
+#else
     if (_refMutex)
     {
         OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*_refMutex); 
@@ -132,10 +156,14 @@ inline void Referenced::ref() const
     {
         ++_refCount;
     }
+#endif
 }
 
 inline void Referenced::unref() const
 {
+#if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
+    bool needDelete = (--_refCount == 0);
+#else
     bool needDelete = false;
     if (_refMutex)
     {
@@ -148,6 +176,7 @@ inline void Referenced::unref() const
         --_refCount;
         needDelete = _refCount<=0;
     }
+#endif
 
     if (needDelete)
     {