Fix thread affinity for charListObtained slot

The connection between QWinRTLowEnergyServiceHandler::charListObtained
and a corresponding lambda was established using a 3-argument version
of QObject::connect, which is implying Qt::DirectConnection.
This means that the lambda was actually executed on the same helper
thread that was responsible for reading characteristics.
This is not the intentional behavior, because it could result in a
concurrent access to serviceList. Also registerForValueChanges()
could be called from multiple threads.

This patch uses the 4-argument version of QObject::connect, so that
Qt::AutoConnection is used. It means that the lambda will be executed
on the main thread.

This patch also removes a duplicated call to thread->exit() from the
lambda. The original call is already performed in a method that emits
the signal. It was not an issue with Qt::DirectConnection, but can be
a problem with the fixed behavior.

Task-number: QTBUG-97578
Change-Id: Ia363489024e46e2879a4bd5e56c2ab8cd6606306
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
(cherry picked from commit 4ecc718d418689b9b9b66086ef4d041a21f44327)

2 files changed, 4 insertions, 7 deletions

diff --git a/src/bluetooth/qlowenergycontroller_winrt.cpp b/src/bluetooth/qlowenergycontroller_winrt.cpp
index 6a039337..9109102e 100644
--- a/src/bluetooth/qlowenergycontroller_winrt.cpp
+++ b/src/bluetooth/qlowenergycontroller_winrt.cpp
@@ -644,8 +644,8 @@ void QLowEnergyControllerPrivateWinRT::discoverServiceDetails(const QBluetoothUu
     connect(thread, &QThread::started, worker, &QWinRTLowEnergyServiceHandler::obtainCharList);
     connect(thread, &QThread::finished, thread, &QObject::deleteLater);
     connect(thread, &QThread::finished, worker, &QObject::deleteLater);
-    connect(worker, &QWinRTLowEnergyServiceHandler::charListObtained,
-            [this, thread](const QBluetoothUuid &service, QHash<QLowEnergyHandle, QLowEnergyServicePrivate::CharData> charList
+    connect(worker, &QWinRTLowEnergyServiceHandler::charListObtained, this,
+            [this](const QBluetoothUuid &service, QHash<QLowEnergyHandle, QLowEnergyServicePrivate::CharData> charList
             , QVector<QBluetoothUuid> indicateChars
             , QLowEnergyHandle startHandle, QLowEnergyHandle endHandle) {
         if (!serviceList.contains(service)) {
@@ -668,7 +668,6 @@ void QLowEnergyControllerPrivateWinRT::discoverServiceDetails(const QBluetoothUu
         Q_ASSERT_SUCCEEDED(hr);
 
         pointer->setState(QLowEnergyService::ServiceDiscovered);
-        thread->exit(0);
     });
     thread->start();
 }
diff --git a/src/bluetooth/qlowenergycontroller_winrt_new.cpp b/src/bluetooth/qlowenergycontroller_winrt_new.cpp
index ed082ba1..5f8d5de5 100644
--- a/src/bluetooth/qlowenergycontroller_winrt_new.cpp
+++ b/src/bluetooth/qlowenergycontroller_winrt_new.cpp
@@ -1170,8 +1170,8 @@ void QLowEnergyControllerPrivateWinRTNew::discoverServiceDetails(const QBluetoot
     connect(thread, &QThread::finished, worker, &QObject::deleteLater);
     connect(worker, &QWinRTLowEnergyServiceHandlerNew::errorOccured,
             this, &QLowEnergyControllerPrivateWinRTNew::handleServiceHandlerError);
-    connect(worker, &QWinRTLowEnergyServiceHandlerNew::charListObtained,
-            [this, reactOnDiscoveryError, thread](const QBluetoothUuid &service, QHash<QLowEnergyHandle,
+    connect(worker, &QWinRTLowEnergyServiceHandlerNew::charListObtained, this,
+            [this, reactOnDiscoveryError](const QBluetoothUuid &service, QHash<QLowEnergyHandle,
             QLowEnergyServicePrivate::CharData> charList, QVector<QBluetoothUuid> indicateChars,
             QLowEnergyHandle startHandle, QLowEnergyHandle endHandle) {
         if (!serviceList.contains(service)) {
@@ -1194,12 +1194,10 @@ void QLowEnergyControllerPrivateWinRTNew::discoverServiceDetails(const QBluetoot
         if (FAILED(hr)) {
             reactOnDiscoveryError(pointer,
                              QStringLiteral("Could not register for value changes in Xaml thread: %1").arg(hr));
-            thread->exit(0);
             return;
         }
 
         pointer->setState(QLowEnergyService::ServiceDiscovered);
-        thread->exit(0);
     });
     thread->start();
 }