QThreadPool: add waitForDone() based on QDeadlineTimer

It was already being used internally this way, so all we needed was to
provide the front-end API and inline the old API.

[ChangeLog][QtCore][QThreadPool] Added an overload of waitForDone()
based on QDeadlineTimer.

Fixes: QTBUG-125107
Change-Id: Ic5b1273bb0204c31afd8fffd17ccf7c5bee07c35
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

src/corelib/compat/removed_api.cpp

@@ -1078,6 +1078,10 @@ bool QRegularExpression::operator==(const QRegularExpression &other) const
 
 #include "qstring.h" // inlined API
 
+#if QT_CONFIG(thread)
+#  include "qthreadpool.h" // inlined API
+#endif
+
 #include "qurl.h"
 
 bool QUrl::operator<(const QUrl &url) const

src/corelib/thread/qthreadpool.cpp

@@ -258,7 +258,7 @@ void QThreadPoolPrivate::startThread(QRunnable *runnable)
 /*!
     \internal
 
-    Helper function only to be called from waitForDone(int)
+    Helper function only to be called from waitForDone()
 
     Deletes all current threads.
 */
@@ -285,22 +285,17 @@ void QThreadPoolPrivate::reset()
 /*!
     \internal
 
-    Helper function only to be called from waitForDone(int)
+    Helper function only to be called from the public waitForDone()
 */
 bool QThreadPoolPrivate::waitForDone(const QDeadlineTimer &timer)
 {
+    QMutexLocker locker(&mutex);
     while (!(queue.isEmpty() && activeThreads == 0) && !timer.hasExpired())
         noActiveThreads.wait(&mutex, timer);
 
-    return queue.isEmpty() && activeThreads == 0;
-}
-
-bool QThreadPoolPrivate::waitForDone(int msecs)
-{
-    QMutexLocker locker(&mutex);
-    QDeadlineTimer timer(msecs);
-    if (!waitForDone(timer))
+    if (!queue.isEmpty() || activeThreads)
         return false;
+
     reset();
     // New jobs might have started during reset, but return anyway
     // as the active thread and task count did reach 0 once, and
@@ -808,15 +803,24 @@ void QThreadPool::startOnReservedThread(QRunnable *runnable)
 */
 
 /*!
+    \fn bool QThreadPool::waitForDone(int msecs)
     Waits up to \a msecs milliseconds for all threads to exit and removes all
     threads from the thread pool. Returns \c true if all threads were removed;
-    otherwise it returns \c false. If \a msecs is -1 (the default), the timeout
-    is ignored (waits for the last thread to exit).
+    otherwise it returns \c false. If \a msecs is -1, this function waits for
+    the last thread to exit.
 */
-bool QThreadPool::waitForDone(int msecs)
+
+/*!
+    \since 6.8
+
+    Waits until \a deadline expires for all threads to exit and removes all
+    threads from the thread pool. Returns \c true if all threads were removed;
+    otherwise it returns \c false.
+*/
+bool QThreadPool::waitForDone(QDeadlineTimer deadline)
 {
     Q_D(QThreadPool);
-    return d->waitForDone(msecs);
+    return d->waitForDone(deadline);
 }
 
 /*!

src/corelib/thread/qthreadpool.h

@@ -72,7 +72,9 @@ public:
     void reserveThread();
     void releaseThread();
 
-    bool waitForDone(int msecs = -1);
+    QT_CORE_INLINE_SINCE(6, 8)
+    bool waitForDone(int msecs);
+    bool waitForDone(QDeadlineTimer deadline = QDeadlineTimer::Forever);
 
     void clear();
 
@@ -103,6 +105,13 @@ void QThreadPool::startOnReservedThread(Callable &&functionToRun)
     startOnReservedThread(QRunnable::create(std::forward<Callable>(functionToRun)));
 }
 
+#if QT_CORE_INLINE_IMPL_SINCE(6, 8)
+bool QThreadPool::waitForDone(int msecs)
+{
+    return waitForDone(QDeadlineTimer(msecs));
+}
+#endif
+
 QT_END_NAMESPACE
 
 #endif

src/corelib/thread/qthreadpool_p.h

@@ -128,7 +128,6 @@ public:
     { return qMax(requestedMaxThreadCount, 1); }    // documentation says we start at least one
     void startThread(QRunnable *runnable = nullptr);
     void reset();
-    bool waitForDone(int msecs);
     bool waitForDone(const QDeadlineTimer &timer);
     void clear();
     void stealAndRunRunnable(QRunnable *runnable);