Detect double timer during single timeout in registerTimer test, and skip

We observe this happening on macOS in the CI system, and it might happen
if a VM doesn't get CPU cycles for long enough time so that two timers
time out. Then event processing will process two timer events, and we
overwrite the timerIdFromEvent with the second event.

Instead, skip the test when this happens.

This is an ammendment to 5c520f4b0ad4b539dc0184c764ca9f12c98730d9

Change-Id: Ibc1169b5458c8dce9d4fe9ce715f49c396e17b86
Fixes: QTBUG-71751
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 17 insertions, 5 deletions

diff --git a/tests/auto/corelib/kernel/qeventdispatcher/tst_qeventdispatcher.cpp b/tests/auto/corelib/kernel/qeventdispatcher/tst_qeventdispatcher.cpp
index 025106a81f..85a2dae3b6 100644
--- a/tests/auto/corelib/kernel/qeventdispatcher/tst_qeventdispatcher.cpp
+++ b/tests/auto/corelib/kernel/qeventdispatcher/tst_qeventdispatcher.cpp
@@ -45,8 +45,10 @@ class tst_QEventDispatcher : public QObject
     Q_OBJECT
 
     QAbstractEventDispatcher *eventDispatcher;
-    int receivedEventType;
-    int timerIdFromEvent;
+
+    int receivedEventType = -1;
+    int timerIdFromEvent = -1;
+    bool doubleTimer = false;
 
 protected:
     bool event(QEvent *e);
@@ -54,9 +56,7 @@ protected:
 public:
     inline tst_QEventDispatcher()
         : QObject(),
-          eventDispatcher(QAbstractEventDispatcher::instance(thread())),
-          receivedEventType(-1),
-          timerIdFromEvent(-1)
+          eventDispatcher(QAbstractEventDispatcher::instance(thread()))
     { }
 
 private slots:
@@ -75,6 +75,9 @@ bool tst_QEventDispatcher::event(QEvent *e)
     switch (receivedEventType = e->type()) {
     case QEvent::Timer:
     {
+        // sometimes, two timers fire during a single QTRY_xxx wait loop
+        if (timerIdFromEvent != -1)
+            doubleTimer = true;
         timerIdFromEvent = static_cast<QTimerEvent *>(e)->timerId();
         return true;
     }
@@ -220,12 +223,17 @@ void tst_QEventDispatcher::registerTimer()
     // process events, waiting for the next event... this should only fire the precise timer
     receivedEventType = -1;
     timerIdFromEvent = -1;
+    doubleTimer = false;
     QTRY_COMPARE_WITH_TIMEOUT(receivedEventType, int(QEvent::Timer), PreciseTimerInterval * 2);
+
 #ifdef Q_OS_DARWIN
+    if (doubleTimer)
+        QSKIP("Double timer during a single timeout - aborting test as flaky on macOS");
     if (timerIdFromEvent != timers.preciseTimerId()
         && elapsedTimer.elapsed() > PreciseTimerInterval * 3)
         QSKIP("Ignore flaky test behavior due to VM scheduling on macOS");
 #endif
+
     QCOMPARE(timerIdFromEvent, timers.preciseTimerId());
     // now unregister it and make sure it's gone
     timers.unregister(timers.preciseTimerId());
@@ -239,8 +247,12 @@ void tst_QEventDispatcher::registerTimer()
     // do the same again for the coarse timer
     receivedEventType = -1;
     timerIdFromEvent = -1;
+    doubleTimer = false;
     QTRY_COMPARE_WITH_TIMEOUT(receivedEventType, int(QEvent::Timer), CoarseTimerInterval * 2);
+
 #ifdef Q_OS_DARWIN
+    if (doubleTimer)
+        QSKIP("Double timer during a single timeout - aborting test as flaky on macOS");
     if (timerIdFromEvent != timers.coarseTimerId()
         && elapsedTimer.elapsed() > CoarseTimerInterval * 3)
         QSKIP("Ignore flaky test behavior due to VM scheduling on macOS");