Merge pull request #53 from projectmemetic/master

Sync optimization, fix potential multicore lock train

src/net.cpp

@@ -1519,9 +1519,15 @@ void ThreadMessageHandler(int ncore)
                 if (pnode == pnodeSync)
                     fHaveSyncNode = true;
             }
+
+            // check if one of the other threads has the sync node
+            BOOST_FOREACH(CNode* pnode, vNodesFullSet) {
+                if(pnode == pnodeSync)
+                    fHaveSyncNode = true;
+            }
         }
 
-        if (!fHaveSyncNode)
+        if (!fHaveSyncNode && IsSyncing()) // Only call this if IsSyncing is true
             StartSync(vNodesCopy);
 
         // Poll the connected nodes for messages

src/net.h

@@ -533,9 +533,11 @@ class CNode
         ssSend.GetAndClear(*it);
         nSendSize += (*it).size();
 
+        // Don't attempt optimistic write here, because this may be called from one of the
+        // message handling threads.  Leave it to be processed by the socket handling thread and avoid potential lock train.
         // If write queue empty, attempt "optimistic write"
-        if (it == vSendMsg.begin())
-            SocketSendData(this);
+        //if (it == vSendMsg.begin())
+        //    SocketSendData(this);
 
         LEAVE_CRITICAL_SECTION(cs_vSend);
     }