From d9c06bf25210b3d0b31ee6126e57bcb82c292da1 Mon Sep 17 00:00:00 2001
From: Harald Fernengel <harald.fernengel@nokia.com>
Date: Fri, 4 Feb 2011 10:46:01 +0100
Subject: Revert "Delay creation of the process manager"

This reverts commit daba2c507ad42c66dafa6a29cffa94e9641e0c58.

There's a potential deadlock when a QProcess is created while a
QCoreApplication is instantiated but never executed, or if the main
thread waits() for the child thread.
---
 src/corelib/io/qprocess_unix.cpp        | 30 ++++--------------------------
 src/corelib/kernel/qcoreapplication.cpp | 18 ++++++------------
 src/corelib/kernel/qcoreapplication.h   |  1 -
 src/corelib/kernel/qcoreapplication_p.h |  2 --
 4 files changed, 10 insertions(+), 41 deletions(-)

diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index b120f7f..f9f5362 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -169,27 +169,17 @@ private:
 
 Q_GLOBAL_STATIC(QMutex, processManagerGlobalMutex)
 
-static QProcessManager *processManagerInstance = 0;
-
-static QProcessManager *processManager()
-{
+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);
-
-    if (!processManagerInstance)
-        QProcessPrivate::initializeProcessManager();
-
-    Q_ASSERT(processManagerInstance);
-    return processManagerInstance;
+    static QProcessManager processManager;
+    return &processManager;
 }
 
 QProcessManager::QProcessManager()
 {
-    // can only be called from main thread
-    Q_ASSERT(!qApp || qApp->thread() == QThread::currentThread());
-
 #if defined (QPROCESS_DEBUG)
     qDebug() << "QProcessManager::QProcessManager()";
 #endif
@@ -208,8 +198,6 @@ 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()
@@ -238,8 +226,6 @@ QProcessManager::~QProcessManager()
     if (oldAction.sa_handler != qt_sa_sigchld_handler) {
         ::sigaction(SIGCHLD, &oldAction, 0);
     }
-
-    processManagerInstance = 0;
 }
 
 void QProcessManager::run()
@@ -1306,15 +1292,7 @@ bool QProcessPrivate::startDetached(const QString &program, const QStringList &a
 
 void QProcessPrivate::initializeProcessManager()
 {
-    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);
-    }
+    (void) processManager();
 }
 
 QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 9bd32d1..26a398e 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -392,16 +392,6 @@ 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()
 {
@@ -666,6 +656,12 @@ 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);
@@ -2732,5 +2728,3 @@ 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 024c509..3957158 100644
--- a/src/corelib/kernel/qcoreapplication.h
+++ b/src/corelib/kernel/qcoreapplication.h
@@ -205,7 +205,6 @@ 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 fdceab4..add2a35 100644
--- a/src/corelib/kernel/qcoreapplication_p.h
+++ b/src/corelib/kernel/qcoreapplication_p.h
@@ -85,8 +85,6 @@ public:
     bool sendThroughObjectEventFilters(QObject *, QEvent *);
     bool notify_helper(QObject *, QEvent *);
 
-    void _q_initializeProcessManager();
-
     virtual QString appName() const;
     virtual void createEventDispatcher();
     static void removePostedEvent(QEvent *);
-- 
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