Implement the blocking QtDBus call in terms of the non-blocking one

This simplifies the code a little by having a single code path. More
importantly, we no longer need to call the evil function
dbus_connection_send_with_reply_and_block. That function acquires a lock
on the socket transport inside libdbus-1, which means all threads need
to wait until the one call gets unblocked before they can continue.

To do that, this commit reimplements the QDBus::Block part of
QDBusConnectionPrivate::sendWithReply by reusing the existing call to
sendWithReplyAsync() and then doing a blocking-wait with
QDBusPendingCallPrivate::waitForFinished().

By using (Q)DBusPendingCall and the threaded connection approach (next
commit), now we never block on the socket. That also means the code to
call dbus_pending_call_block() is no longer necessary and the
waitForFinished() function itself can be considerably simplified.

As a side-effect of no longer blocking, a number of pre-existing race
conditions that used to be hidden showed up.

Note: this commit deadlocks without the threading (next commits).

Task-number: QTBUG-43585
Change-Id: Ic5d393bfd36e48a193fcffff13b73754954a3f7d
Reviewed-by: Albert Astals Cid <aacid@kde.org>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/src/dbus/qdbusconnection_p.h b/src/dbus/qdbusconnection_p.h
index 048e255e88..2155bd634c 100644
--- a/src/dbus/qdbusconnection_p.h
+++ b/src/dbus/qdbusconnection_p.h
@@ -223,7 +223,6 @@ public:
     void unregisterService(const QString &serviceName);
 
     bool handleMessage(const QDBusMessage &msg);
-    void waitForFinished(QDBusPendingCallPrivate *pcall);
 
     QDBusMetaObject *findMetaObject(const QString &service, const QString &path,
                                     const QString &interface, QDBusError &error);