Fix a race where QThread::exit() is "lost" when called after start()

QThread::exit() tries to stop all running event loops, but does nothing
if the eventloop has not started yet. This is often the case for short-
exit method on an object that has affinity to the thread. This ensures
that the exit is called from the running eventloop, meaning the exit()
will never be lost.

Task-number: QTBUG-1184
Reviewed-by: Morten Sørvig

3 files changed, 70 insertions, 12 deletions

diff --git a/src/corelib/thread/qthread.cpp b/src/corelib/thread/qthread.cpp
index cb84538..c35eb28 100644
--- a/src/corelib/thread/qthread.cpp
+++ b/src/corelib/thread/qthread.cpp
@@ -174,7 +174,7 @@ void QAdoptedThread::run()
 
 QThreadPrivate::QThreadPrivate(QThreadData *d)
     : QObjectPrivate(), running(false), finished(false), terminated(false),
-      stackSize(0), priority(QThread::InheritPriority), data(d)
+      stackSize(0), priority(QThread::InheritPriority), data(d), object(0)
 {
 #if defined (Q_OS_UNIX)
     thread_id = 0;
@@ -377,6 +377,9 @@ QThread::QThread(QObject *parent)
     Q_D(QThread);
     // fprintf(stderr, "QThreadData %p created for thread %p\n", d->data, this);
     d->data->thread = this;
+
+    d->object = new QThreadPrivateInternalObject;
+    d->object->moveToThread(this);
 }
 
 /*! \internal
@@ -387,6 +390,8 @@ QThread::QThread(QThreadPrivate &dd, QObject *parent)
     Q_D(QThread);
     // fprintf(stderr, "QThreadData %p taken from private data for thread %p\n", d->data, this);
     d->data->thread = this;
+
+    // do not create the internal object for adopted threads
 }
 
 /*!
@@ -408,6 +413,9 @@ QThread::~QThread()
 
         d->data->thread = 0;
     }
+
+    delete d->object;
+    d->object = 0;
 }
 
 /*!
@@ -510,6 +518,21 @@ int QThread::exec()
 void QThread::exit(int returnCode)
 {
     Q_D(QThread);
+    if (d->object) {
+        QMetaObject::invokeMethod(d->object, "exit", Q_ARG(int, returnCode));
+    } else {
+        QMutexLocker locker(&d->mutex);
+        d->data->quitNow = true;
+        for (int i = 0; i < d->data->eventLoops.size(); ++i) {
+            QEventLoop *eventLoop = d->data->eventLoops.at(i);
+            eventLoop->exit(returnCode);
+        }
+    }
+}
+
+void QThreadPrivateInternalObject::exit(int returnCode)
+{
+    QThreadPrivate *d = static_cast<QThreadPrivate *>(QObjectPrivate::get(thread()));
     QMutexLocker locker(&d->mutex);
     d->data->quitNow = true;
     for (int i = 0; i < d->data->eventLoops.size(); ++i) {
diff --git a/src/corelib/thread/qthread_p.h b/src/corelib/thread/qthread_p.h
index 6825718..54ffd80 100644
--- a/src/corelib/thread/qthread_p.h
+++ b/src/corelib/thread/qthread_p.h
@@ -112,6 +112,15 @@ public:
 };
 
 #ifndef QT_NO_THREAD
+
+class QThreadPrivateInternalObject : public QObject
+{
+    Q_OBJECT
+
+public slots:
+    void exit(int);
+};
+
 class QThreadPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QThread)
@@ -156,6 +165,7 @@ public:
     bool terminationEnabled, terminatePending;
 # endif
     QThreadData *data;
+    QThreadPrivateInternalObject *object;
 
     static void createEventDispatcher(QThreadData *data);
 };
diff --git a/tests/auto/qthread/tst_qthread.cpp b/tests/auto/qthread/tst_qthread.cpp
index bd1bc53..871578e 100644
--- a/tests/auto/qthread/tst_qthread.cpp
+++ b/tests/auto/qthread/tst_qthread.cpp
@@ -168,16 +168,18 @@ public slots:
 class Exit_Thread : public Simple_Thread
 {
 public:
+    Exit_Object *object;
     int code;
     int result;
 
     void run()
     {
-        Simple_Thread::run();
-        Exit_Object o;
-        o.thread = this;
-        o.code = code;
-        QTimer::singleShot(100, &o, SLOT(slot()));
+        if (object) {
+            Simple_Thread::run();
+            object->thread = this;
+            object->code = code;
+            QTimer::singleShot(100, object, SLOT(slot()));
+        }
         result = exec();
     }
 };
@@ -211,17 +213,16 @@ public slots:
 class Quit_Thread : public Simple_Thread
 {
 public:
+    Quit_Object *object;
     int result;
 
     void run()
     {
-        {
-            QMutexLocker locker(&mutex);
-            cond.wakeOne();
+        if (object) {
+            Simple_Thread::run();
+            object->thread = this;
+            QTimer::singleShot(100, object, SLOT(slot()));
         }
-        Quit_Object o;
-        o.thread = this;
-        QTimer::singleShot(100, &o, SLOT(slot()));
         result = exec();
     }
 };
@@ -420,6 +421,8 @@ void tst_QThread::stackSize()
 void tst_QThread::exit()
 {
     Exit_Thread thread;
+    thread.object = new Exit_Object;
+    thread.object->moveToThread(&thread);
     thread.code = 42;
     thread.result = 0;
     QVERIFY(!thread.isFinished());
@@ -433,6 +436,16 @@ void tst_QThread::exit()
     QVERIFY(thread.isFinished());
     QVERIFY(!thread.isRunning());
     QCOMPARE(thread.result, thread.code);
+    delete thread.object;
+
+    Exit_Thread thread2;
+    thread2.object = 0;
+    thread2.code = 53;
+    thread2.result = 0;
+    thread2.start();
+    thread2.exit(thread.code);
+    QVERIFY(thread2.wait(five_minutes));
+    QCOMPARE(thread.result, thread.code);
 }
 
 void tst_QThread::start()
@@ -480,6 +493,9 @@ void tst_QThread::terminate()
 void tst_QThread::quit()
 {
     Quit_Thread thread;
+    thread.object = new Quit_Object;
+    thread.object->moveToThread(&thread);
+    thread.result = -1;
     QVERIFY(!thread.isFinished());
     QVERIFY(!thread.isRunning());
     QMutexLocker locker(&thread.mutex);
@@ -491,6 +507,15 @@ void tst_QThread::quit()
     QVERIFY(thread.isFinished());
     QVERIFY(!thread.isRunning());
     QCOMPARE(thread.result, 0);
+    delete thread.object;
+
+    Quit_Thread thread2;
+    thread2.object = 0;
+    thread2.result = -1;
+    thread2.start();
+    thread2.quit();
+    QVERIFY(thread2.wait(five_minutes));
+    QCOMPARE(thread.result, 0);
 }
 
 void tst_QThread::wait()