From 18e3cd65980e1bc01e6af4807cae0bceca25288c Mon Sep 17 00:00:00 2001
From: Olivier Goffart <olivier.goffart@nokia.com>
Date: Fri, 10 Dec 2010 13:20:48 +0100
Subject: QPointer: thread safety

Fix a race condition between the destructor of QPointer and the
destruction of the object living in a different thread.

Task-number: QTBUG-16005
Reviewed-by: Joao
---
 src/corelib/kernel/qobject.cpp       |  2 ++
 tests/auto/qpointer/tst_qpointer.cpp | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 7fe9c52..c3102ea 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -408,6 +408,8 @@ void QMetaObject::removeGuard(QObject **ptr)
     if (!hash || hash->isEmpty())
         return;
     QMutexLocker locker(guardHashLock());
+    if (!*ptr) //check again, under the lock
+        return;
     GuardHash::iterator it = hash->find(*ptr);
     const GuardHash::iterator end = hash->end();
     bool more = false; //if the QObject has more pointer attached to it.
diff --git a/tests/auto/qpointer/tst_qpointer.cpp b/tests/auto/qpointer/tst_qpointer.cpp
index 5a07e41..ce23764 100644
--- a/tests/auto/qpointer/tst_qpointer.cpp
+++ b/tests/auto/qpointer/tst_qpointer.cpp
@@ -73,6 +73,7 @@ private slots:
     void castDuringDestruction();
     void data() const;
     void dataSignature() const;
+    void threadSafety();
 };
 
 tst_QPointer::tst_QPointer()
@@ -345,5 +346,36 @@ void tst_QPointer::dataSignature() const
     }
 }
 
+class TestRunnable : public QObject, public QRunnable {
+    void run() {
+        QPointer<QObject> obj1 = new QObject;
+        QPointer<QObject> obj2 = new QObject;
+        obj1->moveToThread(thread()); // this is the owner thread
+        obj1->deleteLater(); // the delete will happen in the owner thread
+        obj2->moveToThread(thread()); // this is the owner thread
+        obj2->deleteLater(); // the delete will happen in the owner thread
+    }
+};
+
+void tst_QPointer::threadSafety()
+{
+
+    QThread owner;
+    owner.start();
+
+    QThreadPool pool;
+    for (int i = 0; i < 300; i++) {
+        QPointer<TestRunnable> task = new TestRunnable;
+        task->setAutoDelete(true);
+        task->moveToThread(&owner);
+        pool.start(task);
+    }
+    pool.waitForDone();
+
+    owner.quit();
+    owner.wait();
+}
+
+
 QTEST_MAIN(tst_QPointer)
 #include "tst_qpointer.moc"
-- 
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