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Protect global variable g_pointIdMap with mutexes 

The evdev touch handler is thread based and calls
QWindowSystemInterface::handleTouchEvent. The global variable
in qwindowsysteminterface.cpp is used without being protected by mutexes
which causes data loss and crashes when multiple touch screens are used.

Fixes: QTBUG-63584
Change-Id: I8b5bb04cc517fab96ac428b2bd2bc128b2ca1a54
Reviewed-by: Johan Helsing <johan.helsing@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
bb10
Rainer Keller 2019-10-10 13:32:31 +02:00
parent c54083ff93
commit 23d7320852
2 changed files with 7 additions and 0 deletions
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6
src/gui/kernel/qwindowsysteminterface.cpp
View File

@ -617,6 +617,7 @@ bool QWindowSystemInterface::isTouchDeviceRegistered(const QTouchDevice *device)
static int g_nextPointId = 1;
// map from device-independent point id (arbitrary) to "Qt point" ids
QMutex QWindowSystemInterfacePrivate::pointIdMapMutex;
typedef QMap<quint64, int> PointIdMap;
Q_GLOBAL_STATIC(PointIdMap, g_pointIdMap)
@ -634,6 +635,8 @@ Q_GLOBAL_STATIC(PointIdMap, g_pointIdMap)
*/
static int acquireCombinedPointId(quint8 deviceId, int pointId)
{
QMutexLocker locker(&QWindowSystemInterfacePrivate::pointIdMapMutex);
quint64 combinedId64 = (quint64(deviceId) << 32) + pointId;
auto it = g_pointIdMap->constFind(combinedId64);
int uid;
@ -693,6 +696,8 @@ QList<QTouchEvent::TouchPoint>
}
if (states == Qt::TouchPointReleased) {
QMutexLocker locker(&QWindowSystemInterfacePrivate::pointIdMapMutex);
// All points on deviceId have been released.
// Remove all points associated with that device from g_pointIdMap.
// (On other devices, some touchpoints might still be pressed.
@ -712,6 +717,7 @@ QList<QTouchEvent::TouchPoint>
void QWindowSystemInterfacePrivate::clearPointIdMap()
{
QMutexLocker locker(&QWindowSystemInterfacePrivate::pointIdMapMutex);
g_pointIdMap->clear();
g_nextPointId = 1;
}

1
src/gui/kernel/qwindowsysteminterface_p.h
View File

@ -528,6 +528,7 @@ public:
static QWaitCondition eventsFlushed;
static QMutex flushEventMutex;
static QMutex pointIdMapMutex;
static QAtomicInt eventAccepted;
static QList<QTouchEvent::TouchPoint>