qt: Prevent thread/memory leak on exiting RPCConsole

laanwj · luke-jr · commit c12f4e93b9be · 2016-12-02T07:50:11.000Z
Make ownership of the QThread object clear, so that the RPCConsole can wait for the executor thread to quit before shutdown is called. This increases overall thread safety, and prevents some objects from leaking on exit. Github-Pull: #9190 Rebased-From: 693384e
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
@@ -409,6 +409,11 @@ void BitcoinApplication::requestInitialize()
 
 void BitcoinApplication::requestShutdown()
 {
+    // Show a simple window indicating shutdown status
+    // Do this first as some of the steps may take some time below,
+    // for example the RPC console may still be executing a command.
+    ShutdownWindow::showShutdownWindow(window);
+
     qDebug() << __func__ << ": Requesting shutdown";
     startThread();
     window->hide();
@@ -423,9 +428,6 @@ void BitcoinApplication::requestShutdown()
     delete clientModel;
     clientModel = 0;
 
-    // Show a simple window indicating shutdown status
-    ShutdownWindow::showShutdownWindow(window);
-
     // Request shutdown from core thread
     Q_EMIT requestedShutdown();
 }
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
@@ -496,6 +496,12 @@ void BitcoinGUI::setClientModel(ClientModel *clientModel)
             // Disable context menu on tray icon
             trayIconMenu->clear();
         }
+        // Propagate cleared model to child objects
+        rpcConsole->setClientModel(nullptr);
+#ifdef ENABLE_WALLET
+        walletFrame->setClientModel(nullptr);
+#endif // ENABLE_WALLET
+        unitDisplayControl->setOptionsModel(nullptr);
     }
 }
 
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
@@ -288,7 +288,6 @@ RPCConsole::RPCConsole(const PlatformStyle *platformStyle, QWidget *parent) :
     // based timer interface
     RPCSetTimerInterfaceIfUnset(rpcTimerInterface);
 
-    startExecutor();
     setTrafficGraphRange(INITIAL_TRAFFIC_GRAPH_MINS);
 
     ui->detailWidget->hide();
@@ -302,7 +301,6 @@ RPCConsole::RPCConsole(const PlatformStyle *platformStyle, QWidget *parent) :
 RPCConsole::~RPCConsole()
 {
     GUIUtil::saveWindowGeometry("nRPCConsoleWindow", this);
-    Q_EMIT stopExecutor();
     RPCUnsetTimerInterface(rpcTimerInterface);
     delete rpcTimerInterface;
     delete ui;
@@ -466,6 +464,14 @@ void RPCConsole::setClientModel(ClientModel *model)
         autoCompleter = new QCompleter(wordList, this);
         ui->lineEdit->setCompleter(autoCompleter);
         autoCompleter->popup()->installEventFilter(this);
+        // Start thread to execute RPC commands.
+        startExecutor();
+    }
+    if (!model) {
+        // Client model is being set to 0, this means shutdown() is about to be called.
+        // Make sure we clean up the executor thread
+        Q_EMIT stopExecutor();
+        thread.wait();
     }
 }
 
@@ -646,26 +652,24 @@ void RPCConsole::browseHistory(int offset)
 
 void RPCConsole::startExecutor()
 {
-    QThread *thread = new QThread;
     RPCExecutor *executor = new RPCExecutor();
-    executor->moveToThread(thread);
+    executor->moveToThread(&thread);
 
     // Replies from executor object must go to this object
     connect(executor, SIGNAL(reply(int,QString)), this, SLOT(message(int,QString)));
     // Requests from this object must go to executor
     connect(this, SIGNAL(cmdRequest(QString)), executor, SLOT(request(QString)));
 
     // On stopExecutor signal
-    // - queue executor for deletion (in execution thread)
     // - quit the Qt event loop in the execution thread
-    connect(this, SIGNAL(stopExecutor()), executor, SLOT(deleteLater()));
-    connect(this, SIGNAL(stopExecutor()), thread, SLOT(quit()));
-    // Queue the thread for deletion (in this thread) when it is finished
-    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
+    connect(this, SIGNAL(stopExecutor()), &thread, SLOT(quit()));
+    // - queue executor for deletion (in execution thread)
+    connect(&thread, SIGNAL(finished()), executor, SLOT(deleteLater()), Qt::DirectConnection);
+    connect(&thread, SIGNAL(finished()), this, SLOT(test()), Qt::DirectConnection);
 
     // Default implementation of QThread::run() simply spins up an event loop in the thread,
     // which is what we want.
-    thread->start();
+    thread.start();
 }
 
 void RPCConsole::on_tabWidget_currentChanged(int index)
diff --git a/src/qt/rpcconsole.h b/src/qt/rpcconsole.h
@@ -12,6 +12,7 @@
 
 #include <QWidget>
 #include <QCompleter>
+#include <QThread>
 
 class ClientModel;
 class PlatformStyle;
@@ -140,6 +141,7 @@ public Q_SLOTS:
     QMenu *banTableContextMenu;
     int consoleFontSize;
     QCompleter *autoCompleter;
+    QThread thread;
 };
 
 #endif // BITCOIN_QT_RPCCONSOLE_H

Original file line number	Diff line number	Diff line change
`@@ -496,6 +496,12 @@ void BitcoinGUI::setClientModel(ClientModel *clientModel)`
`496`	`496`	`// Disable context menu on tray icon`
`497`	`497`	`trayIconMenu->clear();`
`498`	`498`	`}`
	`499`	`+ // Propagate cleared model to child objects`
	`500`	`+ rpcConsole->setClientModel(nullptr);`
	`501`	`+#ifdef ENABLE_WALLET`
	`502`	`+ walletFrame->setClientModel(nullptr);`
	`503`	`+#endif // ENABLE_WALLET`
	`504`	`+ unitDisplayControl->setOptionsModel(nullptr);`
`499`	`505`	`}`
`500`	`506`	`}`
`501`	`507`