BlackBerry: Restore proper BPS channel in event dispatcher

This change ensures that BPS events are delivered to the proper
channel even if the application code would change the channel.

Backport from qtbase: 131b86347384a97a7044942acd723c4ef5669636

Change-Id: Ib2bdd3d973bc51f5ce85eb6ef9adcb3e57093a54
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Kevin Krammer <kevin.krammer@kdab.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>

1 files changed, 36 insertions, 8 deletions

diff --git a/src/corelib/kernel/qeventdispatcher_blackberry.cpp b/src/corelib/kernel/qeventdispatcher_blackberry.cpp
index 784e971..0a8b0a6 100644
--- a/src/corelib/kernel/qeventdispatcher_blackberry.cpp
+++ b/src/corelib/kernel/qeventdispatcher_blackberry.cpp
@@ -55,7 +55,29 @@
 #define qEventDispatcherDebug QT_NO_QDEBUG_MACRO()
 #endif
 
-struct bpsIOHandlerData {
+class BpsChannelScopeSwitcher
+{
+public:
+    BpsChannelScopeSwitcher(int scopeChannel) : innerChannel(scopeChannel)
+    {
+        outerChannel = bps_channel_get_active();
+        if (outerChannel != innerChannel)
+            bps_channel_set_active(innerChannel);
+    }
+
+    ~BpsChannelScopeSwitcher()
+    {
+        if (outerChannel != innerChannel)
+            bps_channel_set_active(outerChannel);
+    }
+
+private:
+    int innerChannel;
+    int outerChannel;
+};
+
+struct bpsIOHandlerData
+{
     bpsIOHandlerData()
         : count(0), readfds(0), writefds(0), exceptfds(0)
     {
@@ -101,7 +123,7 @@ static int bpsIOHandler(int fd, int io_events, void *data)
     // but this only needs to happen once if multiple files become ready at the same time
     if (firstReady) {
         qEventDispatcherDebug << "Sending bpsIOReadyDomain event";
-        // create IO ready event
+        // create unblock event
         bps_event_t *event;
         int result = bps_event_create(&event, bpsUnblockDomain, 0, NULL, NULL);
         if (result != BPS_SUCCESS) {
@@ -109,7 +131,8 @@ static int bpsIOHandler(int fd, int io_events, void *data)
             return BPS_FAILURE;
         }
 
-        // post unblock event to our thread
+        // post unblock event to our thread; in this callback the bps channel is
+        // guarenteed to be the same that was active when bps_add_fd was called
         result = bps_push_event(event);
         if (result != BPS_SUCCESS) {
             qWarning("QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberry: bps_push_event() failed");
@@ -175,6 +198,9 @@ QEventDispatcherBlackberry::~QEventDispatcherBlackberry()
 void QEventDispatcherBlackberry::registerSocketNotifier(QSocketNotifier *notifier)
 {
     Q_ASSERT(notifier);
+    Q_D(QEventDispatcherBlackberry);
+
+    BpsChannelScopeSwitcher channelSwitcher(d->bps_channel);
 
     // Register the fd with bps
     int sockfd = notifier->socket();
@@ -205,8 +231,6 @@ void QEventDispatcherBlackberry::registerSocketNotifier(QSocketNotifier *notifie
         break;
     }
 
-    Q_D(QEventDispatcherBlackberry);
-
     errno = 0;
     int result = bps_add_fd(sockfd, io_events, &bpsIOHandler, d->ioData.data());
 
@@ -216,6 +240,10 @@ void QEventDispatcherBlackberry::registerSocketNotifier(QSocketNotifier *notifie
 
 void QEventDispatcherBlackberry::unregisterSocketNotifier(QSocketNotifier *notifier)
 {
+    Q_D(QEventDispatcherBlackberry);
+
+    BpsChannelScopeSwitcher channelSwitcher(d->bps_channel);
+
     // Allow the base Unix implementation to unregister the fd too
     QEventDispatcherUNIX::unregisterSocketNotifier(notifier);
 
@@ -236,8 +264,6 @@ void QEventDispatcherBlackberry::unregisterSocketNotifier(QSocketNotifier *notif
     if (!io_events)
         return;
 
-    Q_D(QEventDispatcherBlackberry);
-
     errno = 0;
     result = bps_add_fd(sockfd, io_events, &bpsIOHandler, d->ioData.data());
     if (result != BPS_SUCCESS) {
@@ -249,12 +275,14 @@ int QEventDispatcherBlackberry::select(int nfds, fd_set *readfds, fd_set *writef
                                        timeval *timeout)
 {
     Q_UNUSED(nfds);
+    Q_D(QEventDispatcherBlackberry);
+
+    BpsChannelScopeSwitcher channelSwitcher(d->bps_channel);
 
     // Make a note of the start time
     timeval startTime = qt_gettime();
 
     // prepare file sets for bps callback
-    Q_D(QEventDispatcherBlackberry);
     d->ioData->count = 0;
     d->ioData->readfds = readfds;
     d->ioData->writefds = writefds;