From 9dacccd0391219c97c01e89f0547ee002abb1e55 Mon Sep 17 00:00:00 2001
From: Bernd Weimer <bweimer@rim.com>
Date: Thu, 25 Oct 2012 10:53:35 +0200
Subject: 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_unix.cpp | 57 +++++++++++++++++-----------
 1 file changed, 34 insertions(+), 23 deletions(-)

(limited to 'src/corelib/kernel/qeventdispatcher_unix.cpp')

diff --git a/src/corelib/kernel/qeventdispatcher_unix.cpp b/src/corelib/kernel/qeventdispatcher_unix.cpp
index 44715b0553..6c2a610a56 100644
--- a/src/corelib/kernel/qeventdispatcher_unix.cpp
+++ b/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)
 { }
-- 
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