osg学习（二十）osg的线程同步

1、建立同步锁

osgViewer/ViewBase.cpp
void ViewerBase::startThreading()
{
    _endDynamicDrawBlock = new osg::EndOfDynamicDrawBlock(numViewerDoubleBufferedRenderingOperation);
    _startRenderingBarrier = new osg::BarrierOperation(numThreadsOnStartBarrier, osg::BarrierOperation::NO_OPERATION);
    _endRenderingDispatchBarrier = new osg::BarrierOperation(numThreadsOnEndBarrier, _endBarrierOperation);


    for(citr = contexts.begin();
        citr != contexts.end();
        ++citr)
    {        
        osg::GraphicsContext* gc = (*citr);          
gc->getState()->setDynamicObjectRenderingCompletedCallback(_endDynamicDrawBlock.get());
        gc->getGraphicsThread()->add(_startRenderingBarrier.get());
        gc->getGraphicsThread()->add(_endRenderingDispatchBarrier.get());
    }
}

osg/OperationThread.cpp
void OperationThread::add(Operation* operation)
{
    OpenThrea