[PATCH v3 4/6] libcamera: base: thread: Support dispatching for a specific receiver

[Kieran Bingham]

Quoting Milan Zamazal (2025-02-25 15:06:10)
> The Thread::dispatchMessage() function supports filtering messages based
> on their type. It can be useful to also dispatch only messages posted
> for a specific receiver. Add an optional receiver argument to the
> dispatchMessage() function to do so. When set to null (the default
> value), the behaviour of the function is not changed.
> 
> This facility is actually used in followup patches.
> 

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
> ---
>  include/libcamera/base/thread.h |  3 ++-
>  src/libcamera/base/thread.cpp   | 21 +++++++++++++--------
>  2 files changed, 15 insertions(+), 9 deletions(-)
> 
> diff --git a/include/libcamera/base/thread.h b/include/libcamera/base/thread.h
> index 3cbf6398..b9284c2c 100644
> --- a/include/libcamera/base/thread.h
> +++ b/include/libcamera/base/thread.h
> @@ -48,7 +48,8 @@ public:
>  
>         EventDispatcher *eventDispatcher();
>  
> -       void dispatchMessages(Message::Type type = Message::Type::None);
> +       void dispatchMessages(Message::Type type = Message::Type::None,
> +                             Object *receiver = nullptr);
>  
>  protected:
>         int exec();
> diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
> index 319bfda9..4de356c7 100644
> --- a/src/libcamera/base/thread.cpp
> +++ b/src/libcamera/base/thread.cpp
> @@ -604,10 +604,12 @@ void Thread::removeMessages(Object *receiver)
>  /**
>   * \brief Dispatch posted messages for this thread
>   * \param[in] type The message type
> + * \param[in] receiver The receiver whose messages to dispatch
>   *
> - * This function immediately dispatches all the messages previously posted for
> - * this thread with postMessage() that match the message \a type. If the \a type
> - * is Message::Type::None, all messages are dispatched.
> + * This function immediately dispatches all the messages of the given \a type
> + * previously posted to this thread for the \a receiver with postMessage(). If
> + * the \a type is Message::Type::None, all messages types are dispatched. If the
> + * \a receiver is null, messages to all receivers are dispatched.
>   *
>   * Messages shall only be dispatched from the current thread, typically within
>   * the thread from the run() function. Calling this function outside of the
> @@ -617,7 +619,7 @@ void Thread::removeMessages(Object *receiver)
>   * same thread from an object's message handler. It guarantees delivery of
>   * messages in the order they have been posted in all cases.
>   */
> -void Thread::dispatchMessages(Message::Type type)
> +void Thread::dispatchMessages(Message::Type type, Object *receiver)
>  {
>         ASSERT(data_ == ThreadData::current());
>  
> @@ -634,6 +636,9 @@ void Thread::dispatchMessages(Message::Type type)
>                 if (type != Message::Type::None && msg->type() != type)
>                         continue;
>  
> +               if (receiver && receiver != msg->receiver_)
> +                       continue;
> +
>                 /*
>                  * Move the message, setting the entry in the list to null. It
>                  * will cause recursive calls to ignore the entry, and the erase
> @@ -641,12 +646,12 @@ void Thread::dispatchMessages(Message::Type type)
>                  */
>                 std::unique_ptr<Message> message = std::move(msg);
>  
> -               Object *receiver = message->receiver_;
> -               ASSERT(data_ == receiver->thread()->data_);
> -               receiver->pendingMessages_--;
> +               Object *messageReceiver = message->receiver_;
> +               ASSERT(data_ == messageReceiver->thread()->data_);
> +               messageReceiver->pendingMessages_--;
>  
>                 locker.unlock();
> -               receiver->message(message.get());
> +               messageReceiver->message(message.get());
>                 message.reset();
>                 locker.lock();
>         }
> -- 
> 2.48.1
>