Removed usage of pipe in Blackberry event dispatcher

Using a pipe for thread wake-ups is inefficient and can introduce significant
latency. Replaced the pipe by directly sending a BPS event.

Refactored the wake-up code in the private class of the UNIX event dispatcher.

Change-Id: Ic073b0b56c3cbf8327fc6bc3c37132cc3583ef86
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Rafael Roquetto <rafael.roquetto@kdab.com>

src/corelib/kernel/qeventdispatcher_blackberry.cpp

@@ -67,7 +67,7 @@ struct bpsIOHandlerData {
     fd_set *exceptfds;
 };
 
-static int bpsIOReadyDomain = -1;
+static int bpsUnblockDomain = -1;
 
 static int bpsIOHandler(int fd, int io_events, void *data)
 {
@@ -103,13 +103,13 @@ static int bpsIOHandler(int fd, int io_events, void *data)
         qEventDispatcherDebug << "Sending bpsIOReadyDomain event";
         // create IO ready event
         bps_event_t *event;
-        int result = bps_event_create(&event, bpsIOReadyDomain, 0, NULL, NULL);
+        int result = bps_event_create(&event, bpsUnblockDomain, 0, NULL, NULL);
         if (result != BPS_SUCCESS) {
             qWarning("QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberry: bps_event_create() failed");
             return BPS_FAILURE;
         }
 
-        // post IO ready event to our thread
+        // post unblock event to our thread
         result = bps_push_event(event);
         if (result != BPS_SUCCESS) {
             qWarning("QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberry: bps_push_event() failed");
@@ -129,31 +129,33 @@ QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberryPrivate()
     if (result != BPS_SUCCESS)
         qFatal("QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberry: bps_initialize() failed");
 
-    // get domain for IO ready events - ignoring race condition here for now
-    if (bpsIOReadyDomain == -1) {
-        bpsIOReadyDomain = bps_register_domain();
-        if (bpsIOReadyDomain == -1)
+    bps_channel = bps_channel_get_active();
+
+    // get domain for IO ready and wake up events - ignoring race condition here for now
+    if (bpsUnblockDomain == -1) {
+        bpsUnblockDomain = bps_register_domain();
+        if (bpsUnblockDomain == -1)
             qWarning("QEventDispatcherBlackberryPrivate::QEventDispatcherBlackberry: bps_register_domain() failed");
     }
-
-    // Register thread_pipe[0] with bps
-    int io_events = BPS_IO_INPUT;
-    result = bps_add_fd(thread_pipe[0], io_events, &bpsIOHandler, ioData.data());
-    if (result != BPS_SUCCESS)
-        qWarning() << Q_FUNC_INFO << "bps_add_fd() failed";
 }
 
 QEventDispatcherBlackberryPrivate::~QEventDispatcherBlackberryPrivate()
 {
-    // Unregister thread_pipe[0] from bps
-    const int result = bps_remove_fd(thread_pipe[0]);
-    if (result != BPS_SUCCESS)
-        qWarning() << Q_FUNC_INFO << "bps_remove_fd() failed";
-
     // we're done using BPS
     bps_shutdown();
 }
 
+int QEventDispatcherBlackberryPrivate::initThreadWakeUp()
+{
+    return -1;  // no fd's used
+}
+
+int QEventDispatcherBlackberryPrivate::processThreadWakeUp(int nsel)
+{
+    Q_UNUSED(nsel);
+    return wakeUps.fetchAndStoreRelaxed(0);
+}
+
 /////////////////////////////////////////////////////////////////////////////
 
 QEventDispatcherBlackberry::QEventDispatcherBlackberry(QObject *parent)
@@ -317,7 +319,7 @@ int QEventDispatcherBlackberry::select(int nfds, fd_set *readfds, fd_set *writef
         if (!event)    // In case of !event, we break out of the loop to let Qt process the timers
             break;     // (since timeout has expired) and socket notifiers that are now ready.
 
-        if (bps_event_get_domain(event) == bpsIOReadyDomain) {
+        if (bps_event_get_domain(event) == bpsUnblockDomain) {
             timeoutTotal = 0;   // in order to immediately drain the event queue of native events
             event = 0;          // (especially touch move events) we don't break out here
         }
@@ -339,6 +341,21 @@ int QEventDispatcherBlackberry::select(int nfds, fd_set *readfds, fd_set *writef
     return d->ioData->count;
 }
 
+void QEventDispatcherBlackberry::wakeUp()
+{
+    Q_D(QEventDispatcherBlackberry);
+    if (d->wakeUps.testAndSetAcquire(0, 1)) {
+        bps_event_t *event;
+        if (bps_event_create(&event, bpsUnblockDomain, 0, 0, 0) == BPS_SUCCESS) {
+            if (bps_channel_push_event(d->bps_channel, event) == BPS_SUCCESS)
+                return;
+            else
+                bps_event_destroy(event);
+        }
+        qWarning("QEventDispatcherBlackberryPrivate::wakeUp failed");
+    }
+}
+
 int QEventDispatcherBlackberry::ioEvents(int fd)
 {
     int io_events = 0;

src/corelib/kernel/qeventdispatcher_blackberry_p.h

@@ -71,6 +71,8 @@ public:
     void registerSocketNotifier(QSocketNotifier *notifier);
     void unregisterSocketNotifier(QSocketNotifier *notifier);
 
+    void wakeUp();
+
 protected:
     QEventDispatcherBlackberry(QEventDispatcherBlackberryPrivate &dd, QObject *parent = 0);
 
@@ -89,6 +91,10 @@ public:
     QEventDispatcherBlackberryPrivate();
     ~QEventDispatcherBlackberryPrivate();
 
+    int initThreadWakeUp();
+    int processThreadWakeUp(int nsel);
+
+    int bps_channel;
     QScopedPointer<bpsIOHandlerData> ioData;
 };
 

src/corelib/kernel/qeventdispatcher_unix.cpp

@@ -110,7 +110,7 @@ QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate()
     bool pipefail = false;
 
     // initialize the common parts of the event loop
-#if defined(Q_OS_NACL)
+#if defined(Q_OS_NACL) || defined (Q_OS_BLACKBERRY)
    // do nothing.
 #elif defined(Q_OS_INTEGRITY)
     // INTEGRITY doesn't like a "select" on pipes, so use socketpair instead
@@ -157,7 +157,7 @@ QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate()
 
 QEventDispatcherUNIXPrivate::~QEventDispatcherUNIXPrivate()
 {
-#if defined(Q_OS_NACL)
+#if defined(Q_OS_NACL) || defined (Q_OS_BLACKBERRY)
    // do nothing.
 #elif defined(Q_OS_VXWORKS)
     close(thread_pipe[0]);
@@ -211,8 +211,8 @@ int QEventDispatcherUNIXPrivate::doSelect(QEventLoop::ProcessEventsFlags flags,
             FD_ZERO(&sn_vec[2].select_fds);
         }
 
-        FD_SET(thread_pipe[0], &sn_vec[0].select_fds);
-        highest = qMax(highest, thread_pipe[0]);
+        int wakeUpFd = initThreadWakeUp();
+        highest = qMax(highest, wakeUpFd);
 
         nsel = q->select(highest + 1,
                          &sn_vec[0].select_fds,
@@ -271,25 +271,7 @@ int QEventDispatcherUNIXPrivate::doSelect(QEventLoop::ProcessEventsFlags flags,
         }
     }
 
-    // some other thread woke us up... consume the data on the thread pipe so that
-    // select doesn't immediately return next time
-    int nevents = 0;
-    if (nsel > 0 && FD_ISSET(thread_pipe[0], &sn_vec[0].select_fds)) {
-#if defined(Q_OS_VXWORKS)
-        char c[16];
-        ::read(thread_pipe[0], c, sizeof(c));
-        ::ioctl(thread_pipe[0], FIOFLUSH, 0);
-#else
-        char c[16];
-        while (::read(thread_pipe[0], c, sizeof(c)) > 0)
-            ;
-#endif
-        if (!wakeUps.testAndSetRelease(1, 0)) {
-            // hopefully, this is dead code
-            qWarning("QEventDispatcherUNIX: internal error, wakeUps.testAndSetRelease(1, 0) failed!");
-        }
-        ++nevents;
-    }
+    int nevents = processThreadWakeUp(nsel);
 
     // activate socket notifiers
     if (! (flags & QEventLoop::ExcludeSocketNotifiers) && nsel > 0 && sn_highest >= 0) {
@@ -307,6 +289,35 @@ int QEventDispatcherUNIXPrivate::doSelect(QEventLoop::ProcessEventsFlags flags,
     return (nevents + q->activateSocketNotifiers());
 }
 
+int QEventDispatcherUNIXPrivate::initThreadWakeUp()
+{
+    FD_SET(thread_pipe[0], &sn_vec[0].select_fds);
+    return thread_pipe[0];
+}
+
+int QEventDispatcherUNIXPrivate::processThreadWakeUp(int nsel)
+{
+    if (nsel > 0 && FD_ISSET(thread_pipe[0], &sn_vec[0].select_fds)) {
+        // some other thread woke us up... consume the data on the thread pipe so that
+        // select doesn't immediately return next time
+#if defined(Q_OS_VXWORKS)
+        char c[16];
+        ::read(thread_pipe[0], c, sizeof(c));
+        ::ioctl(thread_pipe[0], FIOFLUSH, 0);
+#else
+        char c[16];
+        while (::read(thread_pipe[0], c, sizeof(c)) > 0)
+            ;
+#endif
+        if (!wakeUps.testAndSetRelease(1, 0)) {
+            // hopefully, this is dead code
+            qWarning("QEventDispatcherUNIX: internal error, wakeUps.testAndSetRelease(1, 0) failed!");
+        }
+        return 1;
+    }
+    return 0;
+}
+
 QEventDispatcherUNIX::QEventDispatcherUNIX(QObject *parent)
     : QAbstractEventDispatcher(*new QEventDispatcherUNIXPrivate, parent)
 { }

src/corelib/kernel/qeventdispatcher_unix_p.h

@@ -144,6 +144,8 @@ public:
     ~QEventDispatcherUNIXPrivate();
 
     int doSelect(QEventLoop::ProcessEventsFlags flags, timeval *timeout);
+    virtual int initThreadWakeUp();
+    virtual int processThreadWakeUp(int nsel);
 
     bool mainThread;
     int thread_pipe[2];