[libcamera-devel] [PATCH 07/18] libcamera: object: Notify objects of thread move
Jacopo Mondi
jacopo at jmondi.org
Thu Aug 15 12:01:06 CEST 2019
Hi Laurent,
On Thu, Aug 15, 2019 at 12:51:55PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> On Thu, Aug 15, 2019 at 11:09:23AM +0200, Jacopo Mondi wrote:
> > On Mon, Aug 12, 2019 at 03:46:31PM +0300, Laurent Pinchart wrote:
> > > 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);
> >
> > I missed why you can't call message(&msg) directly here.
>
> I could do that. I wanted to provide a public function to send messages
> to objects though, and I thought I could then as well use it here. It
> makes no difference today, but maybe we'll have more code in
> sendMessage() tomorrow. We could of course then change this function.
> Should I drop sendMessage() for now ?
>
Not something I feel strong about, just wondering if I were missing
something. Although providing a public 'sendMessage()' and not using
it if not internally might open doors to misuse?
I'll let you judge what's better here
Thanks
j
> > > +}
> > > +
> > > void Object::connect(SignalBase *signal)
> > > {
> > > signals_.push_back(signal);
>
> --
> Regards,
>
> Laurent Pinchart
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