Debugger: Fix race conditions in block mode

Using waitForMessage() in the constructor after registerService() is
_not_ safe: You might get the first message already after the
registerService() and before the waitForMessage() call. Instead,
use QMutex/QWaitCondition to block the initialization. Also make
the use of the block mode explicit, since the service might already
be enabled also for non-blocking modes ...

Change-Id: I387bfe0627c80e2029acff71f86d12cd9ab58de1
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/src/qml/debugger/qv8profilerservice.cpp b/src/qml/debugger/qv8profilerservice.cpp
index 1cd7606416..5cddea755c 100644
--- a/src/qml/debugger/qv8profilerservice.cpp
+++ b/src/qml/debugger/qv8profilerservice.cpp
@@ -45,6 +45,8 @@
 #include <private/qv8profiler_p.h>
 
 #include <QtCore/QHash>
+#include <QtCore/QMutex>
+#include <QtCore/QWaitCondition>
 
 QT_BEGIN_NAMESPACE
 
@@ -96,6 +98,8 @@ public:
     QList<QV8ProfilerData> m_data;
 
     bool initialized;
+    QMutex initializeMutex;
+    QWaitCondition initializeCondition;
     QList<QString> m_ongoing;
 };
 
@@ -104,10 +108,12 @@ QV8ProfilerService::QV8ProfilerService(QObject *parent)
 {
     Q_D(QV8ProfilerService);
 
-    if (registerService() == Enabled) {
-        // ,block mode, client attached
-        while (!d->initialized)
-            waitForMessage();
+    QMutexLocker lock(&d->initializeMutex);
+
+    if (registerService() == Enabled
+            && QQmlDebugService::blockingMode()) {
+        // let's wait for first message ...
+        d->initializeCondition.wait(&d->initializeMutex);
     }
 }
 
@@ -139,6 +145,10 @@ void QV8ProfilerService::stateAboutToBeChanged(QQmlDebugService::State newState)
                                       Q_ARG(QString, title));
         }
         QMetaObject::invokeMethod(this, "sendProfilingData", Qt::BlockingQueuedConnection);
+    } else {
+        // wake up constructor in blocking mode
+        // (we might got disabled before first message arrived)
+        d->initializeCondition.wakeAll();
     }
 }
 
@@ -152,6 +162,8 @@ void QV8ProfilerService::messageReceived(const QByteArray &message)
     QByteArray title;
     ds >> command >> option;
 
+    QMutexLocker lock(&d->initializeMutex);
+
     if (command == "V8PROFILER") {
         ds >>  title;
         QString titleStr = QString::fromUtf8(title);
@@ -172,6 +184,9 @@ void QV8ProfilerService::messageReceived(const QByteArray &message)
         }
     }
 
+    // wake up constructor in blocking mode
+    d->initializeCondition.wakeAll();
+
     QQmlDebugService::messageReceived(message);
 }