Improve checking for event/socket notifiers and timers

Starting/stopping timers from another thread may result in errors that
may not appear until hours, days or weeks after if a release build of
Qt is used with the GLib/UNIX event dispatchers. Such errors may
manifest as warnings such as "QObject::killTimer(): Error: timer id 7
is not valid for object 0x2a51b488 (), timer has not been killed" and
application crashes (e.g. crashes in malloc, realloc and
malloc_consolidate).

Initial-patch-by: Eike Ziller <eike.ziller@digia.com>
Task-number: QTBUG-40636
Change-Id: I2de50d50eb1fc7467fcebb9c73b74d2f85137933
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/corelib/kernel/qwineventnotifier.cpp b/src/corelib/kernel/qwineventnotifier.cpp
index c694237dc3..d2c623d489 100644
--- a/src/corelib/kernel/qwineventnotifier.cpp
+++ b/src/corelib/kernel/qwineventnotifier.cpp
@@ -140,11 +140,11 @@ QWinEventNotifier::QWinEventNotifier(HANDLE hEvent, QObject *parent)
 {
     Q_D(QWinEventNotifier);
     QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.load();
-    if (!eventDispatcher) {
+    if (Q_UNLIKELY(!eventDispatcher)) {
         qWarning("QWinEventNotifier: Can only be used with threads started with QThread");
-    } else {
-        eventDispatcher->registerEventNotifier(this);
+        return;
     }
+    eventDispatcher->registerEventNotifier(this);
     d->enabled = true;
 }
 
@@ -215,6 +215,10 @@ void QWinEventNotifier::setEnabled(bool enable)
     QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.load();
     if (!eventDispatcher) // perhaps application is shutting down
         return;
+    if (Q_UNLIKELY(thread() != QThread::currentThread())) {
+        qWarning("QWinEventNotifier: Event notifiers cannot be enabled or disabled from another thread");
+        return;
+    }
 
     if (enable)
         eventDispatcher->registerEventNotifier(this);