[libcamera-devel] [PATCH 07/18] libcamera: object: Notify objects of thread move

[Laurent Pinchart]

Send a synchronous message to objects just before they get moved to a
new thread. This allows the object to perform any required processing.
EventNotifier and Timer objects will use this mechanism to move
themselves to the new thread's event disaptcher.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/object.h      |  3 +++
 src/libcamera/include/message.h |  1 +
 src/libcamera/message.cpp       |  2 ++
 src/libcamera/object.cpp        | 26 ++++++++++++++++++++++++++
 4 files changed, 32 insertions(+)

diff --git a/include/libcamera/object.h b/include/libcamera/object.h
index 869200a57d8c..14b939a9bd3d 100644
--- a/include/libcamera/object.h
+++ b/include/libcamera/object.h
@@ -27,6 +27,7 @@ public:
 	virtual ~Object();
 
 	void postMessage(std::unique_ptr<Message> msg);
+	void sendMessage(Message *msg);
 
 	template<typename T, typename... Args, typename std::enable_if<std::is_base_of<Object, T>::value>::type * = nullptr>
 	void invokeMethod(void (T::*func)(Args...), Args... args)
@@ -52,6 +53,8 @@ private:
 
 	void invokeMethod(BoundMethodBase *method, void *pack);
 
+	void notifyThreadMove();
+
 	void connect(SignalBase *signal);
 	void disconnect(SignalBase *signal);
 
diff --git a/src/libcamera/include/message.h b/src/libcamera/include/message.h
index 92717e316cc3..1cfde5669ede 100644
--- a/src/libcamera/include/message.h
+++ b/src/libcamera/include/message.h
@@ -23,6 +23,7 @@ public:
 	enum Type {
 		None = 0,
 		InvokeMessage = 1,
+		ThreadMoveMessage = 2,
 		UserMessage = 1000,
 	};
 
diff --git a/src/libcamera/message.cpp b/src/libcamera/message.cpp
index f6c39d40fc73..efafb655c17e 100644
--- a/src/libcamera/message.cpp
+++ b/src/libcamera/message.cpp
@@ -47,6 +47,8 @@ std::atomic_uint Message::nextUserType_{ Message::UserMessage };
  * \brief Invalid message type
  * \var Message::InvokeMessage
  * \brief Asynchronous method invocation across threads
+ * \var Message::ThreadMoveMessage
+ * \brief Object is being moved to a different thread
  * \var Message::UserMessage
  * \brief First value available for user-defined messages
  */
diff --git a/src/libcamera/object.cpp b/src/libcamera/object.cpp
index 7d70ce21b5d0..7c68ec01f78c 100644
--- a/src/libcamera/object.cpp
+++ b/src/libcamera/object.cpp
@@ -74,6 +74,20 @@ void Object::postMessage(std::unique_ptr<Message> msg)
 	thread()->postMessage(std::move(msg), this);
 }
 
+/**
+ * \brief Send a message directly to the object
+ * \param[in] msg The message
+ *
+ * This method sends the message \a msg directly to the object, delivering it
+ * synchronously through the message() method in the current thread. Message
+ * ownership is not passed to the method, and the caller shall delete the
+ * message after this call.
+ */
+void Object::sendMessage(Message *msg)
+{
+	message(msg);
+}
+
 /**
  * \brief Message handler for the object
  * \param[in] msg The message
@@ -135,6 +149,10 @@ void Object::invokeMethod(BoundMethodBase *method, void *args)
  * This method moves the object from the current thread to the new \a thread.
  * It shall be called from the thread in which the object currently lives,
  * otherwise the behaviour is undefined.
+ *
+ * Before the object is moved, a Message::ThreadMoveMessage message is sent to
+ * it. The message() method can be reimplement in derived classes to be notified
+ * of the upcoming thread move and perform any required processing.
  */
 void Object::moveToThread(Thread *thread)
 {
@@ -143,9 +161,17 @@ void Object::moveToThread(Thread *thread)
 	if (thread_ == thread)
 		return;
 
+	notifyThreadMove();
+
 	thread->moveObject(this);
 }
 
+void Object::notifyThreadMove()
+{
+	Message msg(Message::ThreadMoveMessage);
+	sendMessage(&msg);
+}
+
 void Object::connect(SignalBase *signal)
 {
 	signals_.push_back(signal);
-- 
Regards,

Laurent Pinchart