refs #6362 attempt to fix mutexing issue on Unix

(not fully tested yet on Win but there are hopes. )

Code/Mantid/Framework/Kernel/inc/MantidKernel/MultiThreaded.h

@@ -12,7 +12,8 @@ namespace Kernel
 // Typedefs for ThreadPool
 
 /// General mutex (typedef'd to Poco::FastMutex). Not recursive in general; don't assume it is!
-typedef Poco::FastMutex Mutex;
+  typedef Poco::FastMutex NonRecursiveMutex;
+  typedef Poco::Mutex Mutex;
 
 } //namespace
 } //namespace

Code/Mantid/Framework/Kernel/src/DiskBuffer.cpp

@@ -69,6 +69,7 @@ namespace Kernel
 
     // And put it in the queue of stuff to write.
 //    std::cout << "DiskBuffer adding ID " << item->getId() << " to current size " << m_writeBuffer.size() << std::endl;
+    // TODO: check what happens when the same element is inserted with different size 
     std::pair<writeBuffer_t::iterator,bool> result = m_writeBuffer.insert(item);
 
     // Result.second is FALSE if the item was already there
@@ -95,11 +96,11 @@ namespace Kernel
    */
   void DiskBuffer::objectDeleted(const ISaveable * item)
   {
+    m_mutex.lock();
     // const uint64_t sizeOnFile 
     size_t id = item->getId();
     uint64_t size = item->getDataMemorySize();
 
-    m_mutex.lock();
 
     // Take it out of the to-write buffer
     writeBuffer_byId_t::iterator it2 = m_writeBuffer_byId.find(id);