Turn QThreadData::threadId into a QAtomicPointer

Solves a data race found by TSan.

Since thread and threadId are QAtomicPointer, I've removed the explicit
initialization in the QThreadData constructor

Task-number: QTBUG-58855
Change-Id: I4139d5f93dcb4b429ae9fffd14a34082f2683f76
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qobject.cpp

@@ -3686,7 +3686,7 @@ void QMetaObject::activate(QObject *sender, int signalOffset, int local_signal_i
                 continue;
 
             QObject * const receiver = c->receiver;
-            const bool receiverInSameThread = currentThreadId == receiver->d_func()->threadData->threadId;
+            const bool receiverInSameThread = currentThreadId == receiver->d_func()->threadData->threadId.load();
 
             // determine if this connection should be sent immediately or
             // put into the event queue

src/corelib/thread/qthread.cpp

@@ -56,7 +56,7 @@ QT_BEGIN_NAMESPACE
 */
 
 QThreadData::QThreadData(int initialRefCount)
-    : _ref(initialRefCount), loopLevel(0), scopeLevel(0), thread(0), threadId(0),
+    : _ref(initialRefCount), loopLevel(0), scopeLevel(0),
       eventDispatcher(0),
       quitNow(false), canWait(true), isAdopted(false), requiresCoreApplication(true)
 {

src/corelib/thread/qthread_p.h

@@ -284,7 +284,7 @@ public:
     QStack<QEventLoop *> eventLoops;
     QPostEventList postEventList;
     QAtomicPointer<QThread> thread;
-    Qt::HANDLE threadId;
+    QAtomicPointer<void> threadId;
     QAtomicPointer<QAbstractEventDispatcher> eventDispatcher;
     QVector<void *> tls;
     FlaggedDebugSignatures flaggedSignatures;

src/corelib/thread/qthread_unix.cpp

@@ -255,7 +255,7 @@ QThreadData *QThreadData::current(bool createIfNecessary)
         }
         data->deref();
         data->isAdopted = true;
-        data->threadId = to_HANDLE(pthread_self());
+        data->threadId.store(to_HANDLE(pthread_self()));
         if (!QCoreApplicationPrivate::theMainThread)
             QCoreApplicationPrivate::theMainThread = data->thread.load();
     }
@@ -335,7 +335,7 @@ void *QThreadPrivate::start(void *arg)
             thr->d_func()->setPriority(QThread::Priority(thr->d_func()->priority & ~ThreadPriorityResetFlag));
         }
 
-        data->threadId = to_HANDLE(pthread_self());
+        data->threadId.store(to_HANDLE(pthread_self()));
         set_thread_data(data);
 
         data->ref();
@@ -352,7 +352,7 @@ void *QThreadPrivate::start(void *arg)
         // sets the name of the current thread.
         QString objectName = thr->objectName();
 
-        pthread_t thread_id = from_HANDLE<pthread_t>(data->threadId);
+        pthread_t thread_id = from_HANDLE<pthread_t>(data->threadId.load());
         if (Q_LIKELY(objectName.isEmpty()))
             setCurrentThreadName(thread_id, thr->metaObject()->className());
         else
@@ -651,7 +651,7 @@ void QThread::start(Priority priority)
 #endif
         code = pthread_create(&threadId, &attr, QThreadPrivate::start, this);
     }
-    d->data->threadId = to_HANDLE(threadId);
+    d->data->threadId.store(to_HANDLE(threadId));
 
     pthread_attr_destroy(&attr);
 
@@ -660,7 +660,7 @@ void QThread::start(Priority priority)
 
         d->running = false;
         d->finished = false;
-        d->data->threadId = 0;
+        d->data->threadId.store(nullptr);
     }
 }
 
@@ -670,10 +670,10 @@ void QThread::terminate()
     Q_D(QThread);
     QMutexLocker locker(&d->mutex);
 
-    if (!d->data->threadId)
+    if (!d->data->threadId.load())
         return;
 
-    int code = pthread_cancel(from_HANDLE<pthread_t>(d->data->threadId));
+    int code = pthread_cancel(from_HANDLE<pthread_t>(d->data->threadId.load()));
     if (code) {
         qWarning("QThread::start: Thread termination error: %s",
                  qPrintable(qt_error_string((code))));
@@ -686,7 +686,7 @@ bool QThread::wait(unsigned long time)
     Q_D(QThread);
     QMutexLocker locker(&d->mutex);
 
-    if (from_HANDLE<pthread_t>(d->data->threadId) == pthread_self()) {
+    if (from_HANDLE<pthread_t>(d->data->threadId.load()) == pthread_self()) {
         qWarning("QThread::wait: Thread tried to wait on itself");
         return false;
     }
@@ -728,7 +728,7 @@ void QThreadPrivate::setPriority(QThread::Priority threadPriority)
     int sched_policy;
     sched_param param;
 
-    if (pthread_getschedparam(from_HANDLE<pthread_t>(data->threadId), &sched_policy, &param) != 0) {
+    if (pthread_getschedparam(from_HANDLE<pthread_t>(data->threadId.load()), &sched_policy, &param) != 0) {
         // failed to get the scheduling policy, don't bother setting
         // the priority
         qWarning("QThread::setPriority: Cannot get scheduler parameters");
@@ -744,15 +744,15 @@ void QThreadPrivate::setPriority(QThread::Priority threadPriority)
     }
 
     param.sched_priority = prio;
-    int status = pthread_setschedparam(from_HANDLE<pthread_t>(data->threadId), sched_policy, &param);
+    int status = pthread_setschedparam(from_HANDLE<pthread_t>(data->threadId.load()), sched_policy, &param);
 
 # ifdef SCHED_IDLE
     // were we trying to set to idle priority and failed?
     if (status == -1 && sched_policy == SCHED_IDLE && errno == EINVAL) {
         // reset to lowest priority possible
-        pthread_getschedparam(from_HANDLE<pthread_t>(data->threadId), &sched_policy, &param);
+        pthread_getschedparam(from_HANDLE<pthread_t>(data->threadId.load()), &sched_policy, &param);
         param.sched_priority = sched_get_priority_min(sched_policy);
-        pthread_setschedparam(from_HANDLE<pthread_t>(data->threadId), sched_policy, &param);
+        pthread_setschedparam(from_HANDLE<pthread_t>(data->threadId.load()), sched_policy, &param);
     }
 # else
     Q_UNUSED(status);

src/corelib/thread/qthread_win.cpp

@@ -137,7 +137,7 @@ QThreadData *QThreadData::current(bool createIfNecessary)
         }
         threadData->deref();
         threadData->isAdopted = true;
-        threadData->threadId = reinterpret_cast<Qt::HANDLE>(quintptr(GetCurrentThreadId()));
+        threadData->threadId.store(reinterpret_cast<Qt::HANDLE>(quintptr(GetCurrentThreadId())));
 
         if (!QCoreApplicationPrivate::theMainThread) {
             QCoreApplicationPrivate::theMainThread = threadData->thread.load();
@@ -351,7 +351,7 @@ unsigned int __stdcall QT_ENSURE_STACK_ALIGNED_FOR_SSE QThreadPrivate::start(voi
 
     qt_create_tls();
     TlsSetValue(qt_current_thread_data_tls_index, data);
-    data->threadId = reinterpret_cast<Qt::HANDLE>(quintptr(GetCurrentThreadId()));
+    data->threadId.store(reinterpret_cast<Qt::HANDLE>(quintptr(GetCurrentThreadId())));
 
     QThread::setTerminationEnabled(false);