Add QThreadPool::stackSize

Allows setting the stack size for the thread pool
worker threads. Implemented using QThread::stackSize.

Task-number: QTBUG-2568
Change-Id: Ic7f3981289290685195bbaee977a23e0c3c49bf0
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/corelib/thread/qthreadpool.cpp

@@ -74,7 +74,9 @@ public:
 */
 QThreadPoolThread::QThreadPoolThread(QThreadPoolPrivate *manager)
     :manager(manager), runnable(0)
-{ }
+{
+    setStackSize(manager->stackSize);
+}
 
 /*
     \internal
@@ -604,6 +606,30 @@ void QThreadPool::reserveThread()
     ++d->reservedThreads;
 }
 
+/*! \property QThreadPool::stacksize
+
+    This property contains the stack size for the thread pool worker
+    threads.
+
+    The value of the property is uses when the thread pool creates
+    new threads only. Changing it has no effect for already created
+    or running threads.
+
+    The default value is 0, which makes QThread use the operating
+    system default stack stize.
+*/
+void QThreadPool::setStackSize(uint stackSize)
+{
+    Q_D(QThreadPool);
+    d->stackSize = stackSize;
+}
+
+uint QThreadPool::stackSize() const
+{
+    Q_D(const QThreadPool);
+    return d->stackSize;
+}
+
 /*!
     Releases a thread previously reserved by a call to reserveThread().
 

src/corelib/thread/qthreadpool.h

@@ -58,6 +58,7 @@ class Q_CORE_EXPORT QThreadPool : public QObject
     Q_PROPERTY(int expiryTimeout READ expiryTimeout WRITE setExpiryTimeout)
     Q_PROPERTY(int maxThreadCount READ maxThreadCount WRITE setMaxThreadCount)
     Q_PROPERTY(int activeThreadCount READ activeThreadCount)
+    Q_PROPERTY(uint stackSize READ stackSize WRITE setStackSize)
     friend class QFutureInterfaceBase;
 
 public:
@@ -77,6 +78,9 @@ public:
 
     int activeThreadCount() const;
 
+    void setStackSize(uint stackSize);
+    uint stackSize() const;
+
     void reserveThread();
     void releaseThread();
 

src/corelib/thread/qthreadpool_p.h

@@ -96,6 +96,7 @@ public:
     int maxThreadCount = QThread::idealThreadCount();
     int reservedThreads = 0;
     int activeThreads = 0;
+    uint stackSize = 0;
     bool isExiting = false;
 };
 

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

@@ -92,6 +92,7 @@ private slots:
     void tryTake();
     void waitForDoneTimeout();
     void destroyingWaitsForTasksToFinish();
+    void stackSize();
     void stressTest();
 
 private:
@@ -1136,6 +1137,39 @@ void tst_QThreadPool::destroyingWaitsForTasksToFinish()
     }
 }
 
+// Verify that QThreadPool::stackSize is used when creating
+// new threads. Note that this tests the Qt property only
+// since QThread::stackSize() does not reflect the actual
+// stack size used by the native thread.
+void tst_QThreadPool::stackSize()
+{
+    uint targetStackSize = 512 * 1024;
+    uint threadStackSize = 1; // impossible value
+
+    class StackSizeChecker : public QRunnable
+    {
+        public:
+        uint *stackSize;
+
+        StackSizeChecker(uint *stackSize)
+        :stackSize(stackSize)
+        {
+
+        }
+
+        void run()
+        {
+            *stackSize = QThread::currentThread()->stackSize();
+        }
+    };
+
+    QThreadPool threadPool;
+    threadPool.setStackSize(targetStackSize);
+    threadPool.start(new StackSizeChecker(&threadStackSize));
+    QVERIFY(threadPool.waitForDone(30000)); // 30s timeout
+    QCOMPARE(threadStackSize, targetStackSize);
+}
+
 void tst_QThreadPool::stressTest()
 {
     class Task : public QRunnable