QThreadPool: Add Quality of Service API

Same limitation as setting priority; it only applies to threads that
start after the call.

Change-Id: I0f77467a76ce2f4e7743d04fde344ef08cd8dbb8
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/corelib/thread/qthreadpool.cpp

@@ -249,6 +249,7 @@ void QThreadPoolPrivate::startThread(QRunnable *runnable)
     if (objectName.isEmpty())
         objectName = u"Thread (pooled)"_s;
     thread->setObjectName(objectName);
+    thread->setServiceLevel(serviceLevel);
     Q_ASSERT(!allThreads.contains(thread.get())); // if this assert hits, we have an ABA problem (deleted threads don't get removed here)
     allThreads.insert(thread.get());
     ++activeThreads;
@@ -764,6 +765,38 @@ void QThreadPool::releaseThread()
     d->tryToStartMoreThreads();
 }
 
+/*!
+    \since 6.9
+
+    Sets the Quality of Service level of thread objects created after the call
+    to this setter to \a serviceLevel.
+
+    Support is not available on every platform. Consult
+    QThread::setServiceLevel() for details.
+
+    \sa serviceLevel(), QThread::serviceLevel()
+*/
+void QThreadPool::setServiceLevel(QThread::QualityOfService serviceLevel)
+{
+    Q_D(QThreadPool);
+    QMutexLocker locker(&d->mutex);
+    d->serviceLevel = serviceLevel;
+}
+
+/*!
+    \since 6.9
+
+    Returns the current Quality of Service level of the thread.
+
+    \sa setServiceLevel(), QThread::serviceLevel()
+*/
+QThread::QualityOfService QThreadPool::serviceLevel() const
+{
+    Q_D(const QThreadPool);
+    QMutexLocker locker(&d->mutex);
+    return d->serviceLevel;
+}
+
 /*!
     Releases a thread previously reserved with reserveThread() and uses it
     to run \a runnable.

src/corelib/thread/qthreadpool.h

@@ -72,6 +72,9 @@ public:
     void reserveThread();
     void releaseThread();
 
+    void setServiceLevel(QThread::QualityOfService serviceLevel);
+    QThread::QualityOfService serviceLevel() const;
+
     QT_CORE_INLINE_SINCE(6, 8)
     bool waitForDone(int msecs);
     bool waitForDone(QDeadlineTimer deadline = QDeadlineTimer::Forever);

src/corelib/thread/qthreadpool_p.h

@@ -149,6 +149,7 @@ public:
     int activeThreads = 0;
     uint stackSize = 0;
     QThread::Priority threadPriority = QThread::InheritPriority;
+    QThread::QualityOfService serviceLevel = QThread::QualityOfService::Auto;
 };
 
 QT_END_NAMESPACE

tests/auto/corelib/thread/qthreadpool/tst_qthreadpool.cpp

@@ -76,6 +76,7 @@ private slots:
     void tryStartCount();
     void priorityStart_data();
     void priorityStart();
+    void qualityOfService();
     void waitForDone();
     void clear();
     void clearWithAutoDelete();
@@ -1046,6 +1047,18 @@ void tst_QThreadPool::priorityStart()
     QCOMPARE(firstStarted.loadRelaxed(), expected);
 }
 
+void tst_QThreadPool::qualityOfService()
+{
+    QThreadPool p;
+    p.setServiceLevel(QThread::QualityOfService::Eco);
+    QThread::QualityOfService level = QThread::QualityOfService::Auto;
+    p.tryStart([&level](){
+        level = QThread::currentThread()->serviceLevel();
+    });
+    QVERIFY(p.waitForDone(QDeadlineTimer(10s)));
+    QCOMPARE(level, QThread::QualityOfService::Eco);
+}
+
 void tst_QThreadPool::waitForDone()
 {
     QElapsedTimer total, pass;