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Fix the QNetworkConnectionManagerPrivate initialisation code. 

The current code was meant to be a thread-safe initialisation that
also ran a couple of extra steps. But it wasn't. While it's ok to call
qAddPostRoutine(), the call to updateConfigurations() was
thread-unsafe. It is possible that another thread got the pointer to
the Private before updateConfigurations() finished.

So instead protect the initialisation with a mutex.

It's possible that the value of the pointer becomes visible to
other processors before the other contained values, so use
atomics here.

To call qAddPostRoutine safely from the main thread, use the trick
of deleteLater() (which is thread-safe) in another thread connecting
to a slot.

Change-Id: If9bab88138755df95a791f34b0be8684207979d7
Reviewed-on: http://codereview.qt-project.org/5028
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
bb10
Thiago Macieira 2011-07-06 00:06:15 +02:00 committed by Qt by Nokia
parent 8fb15f3a75
commit 028a860ac5
2 changed files with 46 additions and 22 deletions
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65
src/network/bearer/qnetworkconfigmanager.cpp
View File

@ -46,34 +46,55 @@
#include <QtCore/qstringlist.h>
#include <QtCore/qcoreapplication.h>
#include <QtCore/qmutex.h>
#include <QtCore/qthread.h>
#include <QtCore/private/qcoreapplication_p.h>
#ifndef QT_NO_BEARERMANAGEMENT
QT_BEGIN_NAMESPACE
#define Q_GLOBAL_STATIC_QAPP_DESTRUCTION(TYPE, NAME) \
static QGlobalStatic<TYPE > this_##NAME \
= { Q_BASIC_ATOMIC_INITIALIZER(0), false }; \
static void NAME##_cleanup() \
{ \
delete this_##NAME.pointer; \
this_##NAME.pointer = 0; \
} \
static TYPE *NAME() \
{ \
if (!this_##NAME.pointer) { \
TYPE *x = new TYPE; \
if (!this_##NAME.pointer.testAndSetOrdered(0, x)) \
delete x; \
else { \
qAddPostRoutine(NAME##_cleanup); \
this_##NAME.pointer->updateConfigurations(); \
} \
} \
return this_##NAME.pointer; \
}
static QBasicAtomicPointer<QNetworkConfigurationManagerPrivate> connManager_ptr;
Q_GLOBAL_STATIC(QMutex, connManager_mutex)
Q_GLOBAL_STATIC_QAPP_DESTRUCTION(QNetworkConfigurationManagerPrivate, connManager);
static void connManager_cleanup()
{
// this is not atomic or thread-safe!
delete connManager_ptr.load();
connManager_ptr.store(0);
}
void QNetworkConfigurationManagerPrivate::addPostRoutine()
{
qAddPostRoutine(connManager_cleanup);
}
static QNetworkConfigurationManagerPrivate *connManager()
{
QNetworkConfigurationManagerPrivate *ptr = connManager_ptr.loadAcquire();
if (!ptr) {
QMutexLocker locker(connManager_mutex());
if (!(ptr = connManager_ptr.loadAcquire())) {
ptr = new QNetworkConfigurationManagerPrivate;
if (QCoreApplicationPrivate::mainThread() == QThread::currentThread()) {
// right thread or no main thread yet
ptr->addPostRoutine();
ptr->updateConfigurations();
} else {
// wrong thread, we need to make the main thread do this
QObject *obj = new QObject;
QObject::connect(obj, SIGNAL(destroyed()), ptr, SLOT(addPostRoutine()), Qt::DirectConnection);
ptr->updateConfigurations(); // this moves us to the main thread
obj->moveToThread(QCoreApplicationPrivate::mainThread());
obj->deleteLater();
}
connManager_ptr.storeRelease(ptr);
}
}
return ptr;
}
QNetworkConfigurationManagerPrivate *qNetworkConfigurationManagerPrivate()
{

3
src/network/bearer/qnetworkconfigmanager_p.h
View File

@ -92,6 +92,8 @@ public:
public Q_SLOTS:
void updateConfigurations();
static void addPostRoutine();
Q_SIGNALS:
void configurationAdded(const QNetworkConfiguration &config);
void configurationRemoved(const QNetworkConfiguration &config);
@ -106,6 +108,7 @@ private Q_SLOTS:
void pollEngines();
private:
Q_INVOKABLE void startPolling();
QTimer *pollTimer;