b0135a1522
The bound method arguments pack will need to be accessed by the method invoker in order to retrieve the method return value when using a blocking connection type. We thus can't delete the pack unconditionally in the bound method target thread. We also can't delete it unconditionally in the invoker's thread, as for queued connections the pack will be used in the target thread after the invoker completes. This shows that ownership of the arguments pack is shared between two contexts. As a result, manage it using std::shared_ptr<>. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
166 lines
3.9 KiB
C++
166 lines
3.9 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2019, Google Inc.
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*
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* message.cpp - Message queue support
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*/
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#include "message.h"
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#include <libcamera/signal.h>
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#include "log.h"
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/**
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* \file message.h
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* \brief Message queue support
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*
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* The messaging API enables inter-thread communication through message
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* posting. Messages can be sent from any thread to any recipient deriving from
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* the Object class.
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*
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* To post a message, the sender allocates it dynamically as instance of a class
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* derived from Message. It then posts the message to an Object recipient
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* through Object::postMessage(). Message ownership is passed to the object,
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* thus the message shall not store any temporary data.
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*
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* The message is delivered in the context of the object's thread, through the
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* Object::message() virtual method. After delivery the message is
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* automatically deleted.
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*/
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namespace libcamera {
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LOG_DEFINE_CATEGORY(Message)
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std::atomic_uint Message::nextUserType_{ Message::UserMessage };
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/**
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* \class Message
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* \brief A message that can be posted to a Thread
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*/
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/**
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* \enum Message::Type
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* \brief The message type
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* \var Message::None
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* \brief Invalid message type
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* \var Message::InvokeMessage
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* \brief Asynchronous method invocation across threads
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* \var Message::ThreadMoveMessage
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* \brief Object is being moved to a different thread
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* \var Message::UserMessage
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* \brief First value available for user-defined messages
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*/
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/**
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* \brief Construct a message object of type \a type
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* \param[in] type The message type
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*/
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Message::Message(Message::Type type)
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: type_(type)
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{
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}
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Message::~Message()
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{
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}
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/**
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* \fn Message::type()
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* \brief Retrieve the message type
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* \return The message type
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*/
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/**
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* \fn Message::receiver()
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* \brief Retrieve the message receiver
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* \return The message receiver
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*/
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/**
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* \brief Reserve and register a custom user-defined message type
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*
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* Custom message types use values starting at Message::UserMessage. Assigning
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* custom types manually may lead to accidental duplicated types. To avoid this
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* problem, this method reserves and returns the next available user-defined
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* message type.
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*
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* The recommended way to use this method is to subclass Message and provide a
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* static accessor for the custom message type.
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*
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* \code{.cpp}
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* class MyCustomMessage : public Message
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* {
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* public:
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* MyCustomMessage() : Message(type()) {}
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*
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* static Message::Type type()
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* {
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* static MessageType type = registerMessageType();
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* return type;
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* }
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* };
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* \endcode
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*
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* \return A new unique message type
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*/
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Message::Type Message::registerMessageType()
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{
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return static_cast<Message::Type>(nextUserType_++);
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}
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/**
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* \class InvokeMessage
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* \brief A message carrying a method invocation across threads
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*/
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/**
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* \brief Construct an InvokeMessage for method invocation on an Object
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* \param[in] method The bound method
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* \param[in] pack The packed method arguments
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* \param[in] semaphore The semaphore used to signal message delivery
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* \param[in] deleteMethod True to delete the \a method when the message is
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* destroyed
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*/
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InvokeMessage::InvokeMessage(BoundMethodBase *method,
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std::shared_ptr<BoundMethodPackBase> pack,
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Semaphore *semaphore, bool deleteMethod)
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: Message(Message::InvokeMessage), method_(method), pack_(pack),
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semaphore_(semaphore), deleteMethod_(deleteMethod)
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{
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}
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InvokeMessage::~InvokeMessage()
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{
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if (deleteMethod_)
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delete method_;
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}
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/**
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* \fn InvokeMessage::semaphore()
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* \brief Retrieve the message semaphore passed to the constructor
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* \return The message semaphore
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*/
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/**
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* \brief Invoke the method bound to InvokeMessage::method_ with arguments
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* InvokeMessage::pack_
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*/
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void InvokeMessage::invoke()
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{
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method_->invokePack(pack_.get());
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}
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/**
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* \var InvokeMessage::method_
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* \brief The method to be invoked
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*/
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/**
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* \var InvokeMessage::pack_
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* \brief The packed method invocation arguments
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*/
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} /* namespace libcamera */
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