Remove superfluous ReleaseSemaphore/WFSO calls

Factor out the dispatching of IO results into a separate function.
Do not increment the semaphore count in waitForAnyNotified just to
decrement it again in _q_notified.

Change-Id: I7d4a04b679bb152ab3a5025513f885aee276d086
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

2 files changed, 16 insertions, 13 deletions

diff --git a/src/corelib/io/qwinoverlappedionotifier.cpp b/src/corelib/io/qwinoverlappedionotifier.cpp
index c6ce15c2c9..c9de6671f7 100644
--- a/src/corelib/io/qwinoverlappedionotifier.cpp
+++ b/src/corelib/io/qwinoverlappedionotifier.cpp
@@ -102,7 +102,8 @@ public:
 
     OVERLAPPED *waitForAnyNotified(int msecs);
     void notify(DWORD numberOfBytes, DWORD errorCode, OVERLAPPED *overlapped);
-    OVERLAPPED *_q_notified();
+    void _q_notified();
+    OVERLAPPED *dispatchNextIoResult();
 
     static QWinIoCompletionPort *iocp;
     static HANDLE iocpInstanceLock;
@@ -302,8 +303,7 @@ OVERLAPPED *QWinOverlappedIoNotifierPrivate::waitForAnyNotified(int msecs)
     const DWORD wfso = WaitForSingleObject(hSemaphore, msecs == -1 ? INFINITE : DWORD(msecs));
     switch (wfso) {
     case WAIT_OBJECT_0:
-        ReleaseSemaphore(hSemaphore, 1, NULL);
-        return _q_notified();
+        return dispatchNextIoResult();
     case WAIT_TIMEOUT:
         return 0;
     default:
@@ -385,17 +385,20 @@ void QWinOverlappedIoNotifierPrivate::notify(DWORD numberOfBytes, DWORD errorCod
         emit q->_q_notify();
 }
 
-OVERLAPPED *QWinOverlappedIoNotifierPrivate::_q_notified()
+void QWinOverlappedIoNotifierPrivate::_q_notified()
+{
+    if (WaitForSingleObject(hSemaphore, 0) == WAIT_OBJECT_0)
+        dispatchNextIoResult();
+}
+
+OVERLAPPED *QWinOverlappedIoNotifierPrivate::dispatchNextIoResult()
 {
     Q_Q(QWinOverlappedIoNotifier);
-    if (WaitForSingleObject(hSemaphore, 0) == WAIT_OBJECT_0) {
-        WaitForSingleObject(hResultsMutex, INFINITE);
-        IOResult ioresult = results.dequeue();
-        ReleaseMutex(hResultsMutex);
-        emit q->notified(ioresult.numberOfBytes, ioresult.errorCode, ioresult.overlapped);
-        return ioresult.overlapped;
-    }
-    return 0;
+    WaitForSingleObject(hResultsMutex, INFINITE);
+    IOResult ioresult = results.dequeue();
+    ReleaseMutex(hResultsMutex);
+    emit q->notified(ioresult.numberOfBytes, ioresult.errorCode, ioresult.overlapped);
+    return ioresult.overlapped;
 }
 
 QT_END_NAMESPACE
diff --git a/src/corelib/io/qwinoverlappedionotifier_p.h b/src/corelib/io/qwinoverlappedionotifier_p.h
index 863f87353e..41945d6556 100644
--- a/src/corelib/io/qwinoverlappedionotifier_p.h
+++ b/src/corelib/io/qwinoverlappedionotifier_p.h
@@ -58,7 +58,7 @@ class Q_CORE_EXPORT QWinOverlappedIoNotifier : public QObject
     Q_OBJECT
     Q_DISABLE_COPY(QWinOverlappedIoNotifier)
     Q_DECLARE_PRIVATE(QWinOverlappedIoNotifier)
-    Q_PRIVATE_SLOT(d_func(), OVERLAPPED *_q_notified())
+    Q_PRIVATE_SLOT(d_func(), void _q_notified())
     friend class QWinIoCompletionPort;
 public:
     QWinOverlappedIoNotifier(QObject *parent = 0);