From ce0210bf0428c135f4684713db5161d8fc954475 Mon Sep 17 00:00:00 2001
From: Andrzej Kapolka <drzej.k@gmail.com>
Date: Tue, 15 Jul 2014 16:52:17 -0700
Subject: [PATCH] The weak shared object hash can be accessed by multiple
 threads, so it must be locked.

---
 libraries/metavoxels/src/SharedObject.cpp | 5 +++++
 libraries/metavoxels/src/SharedObject.h   | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/libraries/metavoxels/src/SharedObject.cpp b/libraries/metavoxels/src/SharedObject.cpp
index d0a1842d31..fc72218e2e 100644
--- a/libraries/metavoxels/src/SharedObject.cpp
+++ b/libraries/metavoxels/src/SharedObject.cpp
@@ -14,6 +14,7 @@
 #include <QItemEditorFactory>
 #include <QMetaProperty>
 #include <QVBoxLayout>
+#include <QWriteLocker>
 
 #include "Bitstream.h"
 #include "MetavoxelUtil.h"
@@ -27,10 +28,12 @@ SharedObject::SharedObject() :
     _remoteID(0),
     _remoteOriginID(0) {
     
+    QWriteLocker locker(&_weakHashLock);
     _weakHash.insert(_id, this);
 }
 
 void SharedObject::setID(int id) {
+    QWriteLocker locker(&_weakHashLock);
     _weakHash.remove(_id);
     _weakHash.insert(_id = id, this);
 }
@@ -41,6 +44,7 @@ void SharedObject::incrementReferenceCount() {
 
 void SharedObject::decrementReferenceCount() {
     if (!_referenceCount.deref()) {
+        QWriteLocker locker(&_weakHashLock);
         _weakHash.remove(_id);
         delete this;
     }
@@ -127,6 +131,7 @@ void SharedObject::dump(QDebug debug) const {
 
 int SharedObject::_lastID = 0;
 WeakSharedObjectHash SharedObject::_weakHash;
+QReadWriteLock SharedObject::_weakHashLock;
 
 void pruneWeakSharedObjectHash(WeakSharedObjectHash& hash) {
     for (WeakSharedObjectHash::iterator it = hash.begin(); it != hash.end(); ) {
diff --git a/libraries/metavoxels/src/SharedObject.h b/libraries/metavoxels/src/SharedObject.h
index ba643b449c..5ff5aa9680 100644
--- a/libraries/metavoxels/src/SharedObject.h
+++ b/libraries/metavoxels/src/SharedObject.h
@@ -17,6 +17,7 @@
 #include <QMetaType>
 #include <QObject>
 #include <QPointer>
+#include <QReadWriteLock>
 #include <QSet>
 #include <QWidget>
 #include <QtDebug>
@@ -36,6 +37,9 @@ public:
     /// Returns the weak hash under which all local shared objects are registered.
     static const WeakSharedObjectHash& getWeakHash() { return _weakHash; }
 
+    /// Returns a reference to the weak hash lock.
+    static QReadWriteLock& getWeakHashLock() { return _weakHashLock; }
+    
     Q_INVOKABLE SharedObject();
 
     /// Returns the unique local ID for this object.
@@ -85,6 +89,7 @@ private:
     
     static int _lastID;
     static WeakSharedObjectHash _weakHash;
+    static QReadWriteLock _weakHashLock;
 };
 
 /// Removes the null references from the supplied hash.