Add some more comments

Add some developer comments explaining which method
is designed to be called from a certain thread.
Add also some comments about in which thread
certain QObjects live in.

Change-Id: I38b10216cc29f8a86fd784e588e913407f0fb776
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/launcherinterface.cpp

@@ -210,11 +210,13 @@ LauncherInterface::~LauncherInterface()
 
 void LauncherInterface::startLauncher()
 {
+    // Call in launcher's thread.
     QMetaObject::invokeMethod(instance().m_private, &LauncherInterfacePrivate::doStart);
 }
 
 void LauncherInterface::stopLauncher()
 {
+    // Call in launcher's thread.
     QMetaObject::invokeMethod(instance().m_private, &LauncherInterfacePrivate::doStop);
 }
 

src/libs/utils/launchersocket.cpp

@@ -39,9 +39,10 @@ class CallerHandle : public QObject
 {
     Q_OBJECT
 public:
+    // Called from caller's thread exclusively, lives in caller's thread.
     CallerHandle() : QObject() {}
 
-    // Always called in caller's thread. Returns the list of flushed signals.
+    // Called from caller's thread exclusively. Returns the list of flushed signals.
     QList<LauncherHandle::SignalType> flush()
     {
         QList<LauncherHandle::SignalType> oldSignals;
@@ -70,17 +71,7 @@ public:
         }
         return oldSignals;
     }
-    void appendSignal(LauncherHandle::SignalType signalType)
+    // Called from caller's thread exclusively.
-    {
-        if (signalType == LauncherHandle::SignalType::NoSignal)
-            return;
-
-        QMutexLocker locker(&m_mutex);
-        if (m_signals.contains(signalType))
-            return;
-
-        m_signals.append(signalType);
-    }
     bool shouldFlushFor(LauncherHandle::SignalType signalType)
     {
         // TODO: Should we always flush when the list isn't empty?
@@ -93,7 +84,20 @@ public:
             return true;
         return false;
     }
+    // Called from launcher's thread exclusively.
+    void appendSignal(LauncherHandle::SignalType signalType)
+    {
+        if (signalType == LauncherHandle::SignalType::NoSignal)
+            return;
+
+        QMutexLocker locker(&m_mutex);
+        if (m_signals.contains(signalType))
+            return;
+
+        m_signals.append(signalType);
+    }
 signals:
+    // Emitted from caller's thread exclusively.
     void errorOccurred();
     void started();
     void readyRead();
@@ -485,7 +489,7 @@ void LauncherSocket::sendData(const QByteArray &data)
         return m_requests.size() == 1; // Returns true if requests handling should be triggered.
     };
 
-    if (storeRequest(data))
+    if (storeRequest(data)) // Call handleRequests() in launcher's thread.
         QMetaObject::invokeMethod(this, &LauncherSocket::handleRequests);
 }
 

src/libs/utils/launchersocket.h

@@ -55,14 +55,11 @@ class CallerHandle;
 // It's assumed that this object will be alive at least
 // as long as the corresponding QtcProcess is alive.
 
-// We should have LauncherSocket::registerHandle() and LauncherSocket::unregisterHandle()
-// methods.
-
 class LauncherHandle : public QObject
 {
     Q_OBJECT
 public:
-    // called from main thread
+    // All the public methods in this class are called exclusively from the caller's thread.
     bool waitForStarted(int msecs)
     { return waitForSignal(msecs, SignalType::Started); }
     bool waitForReadyRead(int msces)
@@ -122,25 +119,30 @@ private:
         ReadyRead,
         Finished
     };
-    // called from other thread
+
+    // Called from caller's thread exclusively.
     bool waitForSignal(int msecs, SignalType newSignal);
     bool doWaitForSignal(int msecs, SignalType newSignal);
     bool canWaitFor(SignalType newSignal) const;
 
+    // Called from caller's or launcher's thread.
     void doStart();
 
+    // Called from caller's thread exclusively.
     void slotErrorOccurred();
     void slotStarted();
     void slotReadyRead();
     void slotFinished();
 
-    // called from this thread
+    // Called from caller's thread, moved to launcher's thread.
     LauncherHandle(quintptr token, ProcessMode mode) : m_token(token), m_processMode(mode) {}
+
+    // Called from caller's thread exclusively.
     void createCallerHandle();
     void destroyCallerHandle();
 
+    // Called from launcher's thread exclusively.
     void flushCaller();
-
     void handlePacket(LauncherPacketType type, const QByteArray &payload);
     void handleErrorPacket(const QByteArray &packetData);
     void handleStartedPacket(const QByteArray &packetData);
@@ -148,18 +150,22 @@ private:
     void handleReadyReadStandardError(const QByteArray &packetData);
     void handleFinishedPacket(const QByteArray &packetData);
 
+    // Called from launcher's thread exclusively.
     void handleSocketReady();
     void handleSocketError(const QString &message);
 
+    // Called from launcher's thread exclusively.
     void wakeUpIfWaitingFor(SignalType newSignal);
 
-    QByteArray readAndClear(QByteArray &data)
+    // Called from caller's thread exclusively.
+    QByteArray readAndClear(QByteArray &data) const
     {
         const QByteArray tmp = data;
         data.clear();
         return tmp;
     }
 
+    // Called from caller's or launcher's thread.
     void sendPacket(const Internal::LauncherPacket &packet);
 
     mutable QMutex m_mutex;
@@ -169,7 +175,8 @@ private:
     SignalType m_waitingFor = SignalType::NoSignal;
 
     QProcess::ProcessState m_processState = QProcess::NotRunning;
-    bool m_awaitingShouldContinue = false; // cancel() sets it to false, modified only in caller's thread
+    // cancel() sets it to false, modified only in caller's thread.
+    bool m_awaitingShouldContinue = false;
     int m_processId = 0;
     int m_exitCode = 0;
     QProcess::ExitStatus m_exitStatus = QProcess::ExitStatus::NormalExit;
@@ -187,6 +194,7 @@ private:
     QProcess::ProcessChannelMode m_channelMode = QProcess::SeparateChannels;
     QString m_standardInputFile;
 
+    // Lives in caller's thread.
     CallerHandle *m_callerHandle = nullptr;
 
     bool m_belowNormalPriority = false;
@@ -203,9 +211,11 @@ class LauncherSocket : public QObject
     Q_OBJECT
     friend class LauncherInterfacePrivate;
 public:
+    // Called from caller's or launcher's thread.
     bool isReady() const { return m_socket.load(); }
     void sendData(const QByteArray &data);
 
+    // Called from caller's thread exclusively.
     LauncherHandle *registerHandle(quintptr token, ProcessMode mode);
     void unregisterHandle(quintptr token);
 
@@ -214,13 +224,17 @@ signals:
     void errorOccurred(const QString &error);
 
 private:
+    // Called from caller's thread, moved to launcher's thread.
     LauncherSocket(QObject *parent = nullptr);
 
+    // Called from launcher's thread exclusively.
     LauncherHandle *handleForToken(quintptr token) const;
 
+    // Called from launcher's thread exclusively.
     void setSocket(QLocalSocket *socket);
     void shutdown();
 
+    // Called from launcher's thread exclusively.
     void handleSocketError();
     void handleSocketDataAvailable();
     void handleSocketDisconnected();

src/libs/utils/qtcprocess.cpp

@@ -310,8 +310,6 @@ private:
     typedef void (ProcessLauncherImpl::*PreSignal)(void);
 
     void cancel();
-    void sendPacket(const Internal::LauncherPacket &packet)
-    { LauncherInterface::socket()->sendData(packet.serialize()); }
 
     void handleSocketError(const QString &message);
     void handleSocketReady();
@@ -319,7 +317,8 @@ private:
     quintptr token() const { return m_token; }
 
     const uint m_token = 0;
-    LauncherHandle *m_handle = nullptr; // This object lives in a different thread!
+    // Lives in launcher's thread.
+    LauncherHandle *m_handle = nullptr;
 };
 
 void ProcessLauncherImpl::cancel()