Delay creation of the process manager

The *nix process manager would create a pipe on every startup. In order
to improve startup speed, the QProcessManager is now created when first
needed.

Reviewed-by: Robert Griebl

4 files changed, 41 insertions, 10 deletions

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index 216c382..e52d132 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -169,17 +169,27 @@ private:
 
 Q_GLOBAL_STATIC(QMutex, processManagerGlobalMutex)
 
-static QProcessManager *processManager() {
+static QProcessManager *processManagerInstance = 0;
+
+static QProcessManager *processManager()
+{
     // The constructor of QProcessManager should be called only once
     // so we cannot use Q_GLOBAL_STATIC directly for QProcessManager
     QMutex *mutex = processManagerGlobalMutex();
     QMutexLocker locker(mutex);
-    static QProcessManager processManager;
-    return &processManager;
+
+    if (!processManagerInstance)
+        QProcessPrivate::initializeProcessManager();
+
+    Q_ASSERT(processManagerInstance);
+    return processManagerInstance;
 }
 
 QProcessManager::QProcessManager()
 {
+    // can only be called from main thread
+    Q_ASSERT(!qApp || qApp->thread() == QThread::currentThread());
+
 #if defined (QPROCESS_DEBUG)
     qDebug() << "QProcessManager::QProcessManager()";
 #endif
@@ -198,6 +208,8 @@ QProcessManager::QProcessManager()
     ::sigaction(SIGCHLD, &action, &oldAction);
     if (oldAction.sa_handler != qt_sa_sigchld_handler)
 	qt_sa_old_sigchld_handler = oldAction.sa_handler;
+
+    processManagerInstance = this;
 }
 
 QProcessManager::~QProcessManager()
@@ -226,6 +238,8 @@ QProcessManager::~QProcessManager()
     if (oldAction.sa_handler != qt_sa_sigchld_handler) {
         ::sigaction(SIGCHLD, &oldAction, 0);
     }
+
+    processManagerInstance = 0;
 }
 
 void QProcessManager::run()
@@ -1289,7 +1303,15 @@ bool QProcessPrivate::startDetached(const QString &program, const QStringList &a
 
 void QProcessPrivate::initializeProcessManager()
 {
-    (void) processManager();
+    if (qApp && qApp->thread() != QThread::currentThread()) {
+        // The process manager must be initialized in the main thread
+        // Note: The call below will re-enter this function, but in the right thread,
+        // so the else statement below will be executed.
+        QMetaObject::invokeMethod(qApp, "_q_initializeProcessManager", Qt::BlockingQueuedConnection);
+    } else {
+        static QProcessManager processManager;
+        Q_UNUSED(processManager);
+    }
 }
 
 QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 0f95ee0..799433b 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -336,6 +336,16 @@ void QCoreApplicationPrivate::createEventDispatcher()
 #endif
 }
 
+void QCoreApplicationPrivate::_q_initializeProcessManager()
+{
+#ifndef QT_NO_PROCESS
+#  ifdef Q_OS_UNIX
+    QProcessPrivate::initializeProcessManager();
+#  endif
+#endif
+}
+
+
 QThread *QCoreApplicationPrivate::theMainThread = 0;
 QThread *QCoreApplicationPrivate::mainThread()
 {
@@ -600,12 +610,6 @@ void QCoreApplication::init()
     }
 #endif
 
-#if defined(Q_OS_UNIX) && !(defined(QT_NO_PROCESS))
-    // Make sure the process manager thread object is created in the main
-    // thread.
-    QProcessPrivate::initializeProcessManager();
-#endif
-
 #ifdef QT_EVAL
     extern void qt_core_eval_init(uint);
     qt_core_eval_init(d->application_type);
@@ -2666,3 +2670,5 @@ int QCoreApplication::loopLevel()
 */
 
 QT_END_NAMESPACE
+
+#include "moc_qcoreapplication.cpp"
diff --git a/src/corelib/kernel/qcoreapplication.h b/src/corelib/kernel/qcoreapplication.h
index f1c7c26..17e784e 100644
--- a/src/corelib/kernel/qcoreapplication.h
+++ b/src/corelib/kernel/qcoreapplication.h
@@ -205,6 +205,7 @@ protected:
     QCoreApplication(QCoreApplicationPrivate &p);
 
 private:
+    Q_PRIVATE_SLOT(d_func(), void _q_initializeProcessManager())
     static bool sendSpontaneousEvent(QObject *receiver, QEvent *event);
     bool notifyInternal(QObject *receiver, QEvent *event);
 
diff --git a/src/corelib/kernel/qcoreapplication_p.h b/src/corelib/kernel/qcoreapplication_p.h
index 2355c37..aafa821 100644
--- a/src/corelib/kernel/qcoreapplication_p.h
+++ b/src/corelib/kernel/qcoreapplication_p.h
@@ -82,6 +82,8 @@ public:
     bool sendThroughObjectEventFilters(QObject *, QEvent *);
     bool notify_helper(QObject *, QEvent *);
 
+    void _q_initializeProcessManager();
+
     virtual QString appName() const;
     virtual void createEventDispatcher();
     static void removePostedEvent(QEvent *);