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Diffstat (limited to 'ext/boost/asio/detail/task_io_service_2lock.hpp')
| -rw-r--r-- | ext/boost/asio/detail/task_io_service_2lock.hpp | 475 |
1 files changed, 475 insertions, 0 deletions
diff --git a/ext/boost/asio/detail/task_io_service_2lock.hpp b/ext/boost/asio/detail/task_io_service_2lock.hpp new file mode 100644 index 0000000000..741ec5776f --- /dev/null +++ b/ext/boost/asio/detail/task_io_service_2lock.hpp @@ -0,0 +1,475 @@ +// +// task_io_service_2lock.hpp +// ~~~~~~~~~~~~~~~~~~~~~~~~~ +// +// Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com) +// +// Distributed under the Boost Software License, Version 1.0. (See accompanying +// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) +// + +#ifndef BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP +#define BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP + +#if defined(_MSC_VER) && (_MSC_VER >= 1200) +# pragma once +#endif // defined(_MSC_VER) && (_MSC_VER >= 1200) + +#include <boost/asio/detail/push_options.hpp> + +#include <boost/asio/io_service.hpp> +#include <boost/asio/detail/call_stack.hpp> +#include <boost/asio/detail/event.hpp> +#include <boost/asio/detail/handler_alloc_helpers.hpp> +#include <boost/asio/detail/handler_invoke_helpers.hpp> +#include <boost/asio/detail/indirect_handler_queue.hpp> +#include <boost/asio/detail/mutex.hpp> +#include <boost/asio/detail/service_base.hpp> +#include <boost/asio/detail/task_io_service_fwd.hpp> + +#include <boost/asio/detail/push_options.hpp> +#include <boost/detail/atomic_count.hpp> +#include <boost/system/error_code.hpp> +#include <boost/asio/detail/pop_options.hpp> + +namespace boost { +namespace asio { +namespace detail { + +// An alternative task_io_service implementation based on a two-lock queue. + +template <typename Task> +class task_io_service + : public boost::asio::detail::service_base<task_io_service<Task> > +{ +public: + typedef indirect_handler_queue handler_queue; + + // Constructor. + task_io_service(boost::asio::io_service& io_service) + : boost::asio::detail::service_base<task_io_service<Task> >(io_service), + front_mutex_(), + back_mutex_(), + task_(0), + outstanding_work_(0), + front_stopped_(false), + back_stopped_(false), + back_shutdown_(false), + back_first_idle_thread_(0), + back_task_thread_(0) + { + } + + void init(size_t /*concurrency_hint*/) + { + } + + // Destroy all user-defined handler objects owned by the service. + void shutdown_service() + { + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + back_shutdown_ = true; + back_lock.unlock(); + + // Destroy handler objects. + while (handler_queue::handler* h = handler_queue_.pop()) + if (h != &task_handler_) + h->destroy(); + + // Reset to initial state. + task_ = 0; + } + + // Initialise the task, if required. + void init_task() + { + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + if (!back_shutdown_ && !task_) + { + task_ = &use_service<Task>(this->get_io_service()); + handler_queue_.push(&task_handler_); + interrupt_one_idle_thread(back_lock); + } + } + + // Run the event loop until interrupted or no more work. + size_t run(boost::system::error_code& ec) + { + if (outstanding_work_ == 0) + { + stop(); + ec = boost::system::error_code(); + return 0; + } + + typename call_stack<task_io_service>::context ctx(this); + + idle_thread_info this_idle_thread; + this_idle_thread.next = 0; + + size_t n = 0; + while (do_one(&this_idle_thread, ec)) + if (n != (std::numeric_limits<size_t>::max)()) + ++n; + return n; + } + + // Run until interrupted or one operation is performed. + size_t run_one(boost::system::error_code& ec) + { + if (outstanding_work_ == 0) + { + stop(); + ec = boost::system::error_code(); + return 0; + } + + typename call_stack<task_io_service>::context ctx(this); + + idle_thread_info this_idle_thread; + this_idle_thread.next = 0; + + return do_one(&this_idle_thread, ec); + } + + // Poll for operations without blocking. + size_t poll(boost::system::error_code& ec) + { + if (outstanding_work_ == 0) + { + stop(); + ec = boost::system::error_code(); + return 0; + } + + typename call_stack<task_io_service>::context ctx(this); + + size_t n = 0; + while (do_one(0, ec)) + if (n != (std::numeric_limits<size_t>::max)()) + ++n; + return n; + } + + // Poll for one operation without blocking. + size_t poll_one(boost::system::error_code& ec) + { + if (outstanding_work_ == 0) + { + stop(); + ec = boost::system::error_code(); + return 0; + } + + typename call_stack<task_io_service>::context ctx(this); + + return do_one(0, ec); + } + + // Interrupt the event processing loop. + void stop() + { + boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_); + front_stopped_ = true; + front_lock.unlock(); + + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + back_stopped_ = true; + interrupt_all_idle_threads(back_lock); + } + + // Reset in preparation for a subsequent run invocation. + void reset() + { + boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_); + front_stopped_ = false; + front_lock.unlock(); + + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + back_stopped_ = false; + } + + // Notify that some work has started. + void work_started() + { + ++outstanding_work_; + } + + // Notify that some work has finished. + void work_finished() + { + if (--outstanding_work_ == 0) + stop(); + } + + // Request invocation of the given handler. + template <typename Handler> + void dispatch(Handler handler) + { + if (call_stack<task_io_service>::contains(this)) + boost_asio_handler_invoke_helpers::invoke(handler, &handler); + else + post(handler); + } + + // Request invocation of the given handler and return immediately. + template <typename Handler> + void post(Handler handler) + { + // Allocate and construct an operation to wrap the handler. + handler_queue::scoped_ptr ptr(handler_queue::wrap(handler)); + + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + + // If the service has been shut down we silently discard the handler. + if (back_shutdown_) + return; + + // Add the handler to the end of the queue. + handler_queue_.push(ptr.get()); + ptr.release(); + + // An undelivered handler is treated as unfinished work. + ++outstanding_work_; + + // Wake up a thread to execute the handler. + interrupt_one_idle_thread(back_lock); + } + +private: + struct idle_thread_info; + + size_t do_one(idle_thread_info* this_idle_thread, + boost::system::error_code& ec) + { + bool task_has_run = false; + for (;;) + { + // The front lock must be held before we can pop items from the queue. + boost::asio::detail::mutex::scoped_lock front_lock(front_mutex_); + if (front_stopped_) + { + ec = boost::system::error_code(); + return 0; + } + + if (handler_queue::handler* h = handler_queue_.pop()) + { + if (h == &task_handler_) + { + bool more_handlers = handler_queue_.poppable(); + unsigned long front_version = handler_queue_.front_version(); + front_lock.unlock(); + + // The task is always added to the back of the queue when we exit + // this block. + task_cleanup c(*this); + + // If we're polling and the task has already run then we're done. + bool polling = !this_idle_thread; + if (task_has_run && polling) + { + ec = boost::system::error_code(); + return 0; + } + + // If we're considering going idle we need to check whether the queue + // is still empty. If it is, add the thread to the list of idle + // threads. + if (!more_handlers && !polling) + { + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + if (back_stopped_) + { + ec = boost::system::error_code(); + return 0; + } + else if (front_version == handler_queue_.back_version()) + { + back_task_thread_ = this_idle_thread; + } + else + { + more_handlers = true; + } + } + + // Run the task. May throw an exception. Only block if the handler + // queue is empty and we're not polling, otherwise we want to return + // as soon as possible. + task_has_run = true; + task_->run(!more_handlers && !polling); + } + else + { + front_lock.unlock(); + handler_cleanup c(*this); + + // Invoke the handler. May throw an exception. + h->invoke(); // invoke() deletes the handler object + + ec = boost::system::error_code(); + return 1; + } + } + else if (this_idle_thread) + { + unsigned long front_version = handler_queue_.front_version(); + front_lock.unlock(); + + // If we're considering going idle we need to check whether the queue + // is still empty. If it is, add the thread to the list of idle + // threads. + boost::asio::detail::mutex::scoped_lock back_lock(back_mutex_); + if (back_stopped_) + { + ec = boost::system::error_code(); + return 0; + } + else if (front_version == handler_queue_.back_version()) + { + this_idle_thread->next = back_first_idle_thread_; + back_first_idle_thread_ = this_idle_thread; + this_idle_thread->wakeup_event.clear(back_lock); + this_idle_thread->wakeup_event.wait(back_lock); + } + } + else + { + ec = boost::system::error_code(); + return 0; + } + } + } + + // Interrupt a single idle thread. + void interrupt_one_idle_thread( + boost::asio::detail::mutex::scoped_lock& back_lock) + { + if (back_first_idle_thread_) + { + idle_thread_info* idle_thread = back_first_idle_thread_; + back_first_idle_thread_ = idle_thread->next; + idle_thread->next = 0; + idle_thread->wakeup_event.signal(back_lock); + } + else if (back_task_thread_ && task_) + { + back_task_thread_ = 0; + task_->interrupt(); + } + } + + // Interrupt all idle threads. + void interrupt_all_idle_threads( + boost::asio::detail::mutex::scoped_lock& back_lock) + { + while (back_first_idle_thread_) + { + idle_thread_info* idle_thread = back_first_idle_thread_; + back_first_idle_thread_ = idle_thread->next; + idle_thread->next = 0; + idle_thread->wakeup_event.signal(back_lock); + } + + if (back_task_thread_ && task_) + { + back_task_thread_ = 0; + task_->interrupt(); + } + } + + // Helper class to perform task-related operations on block exit. + class task_cleanup; + friend class task_cleanup; + class task_cleanup + { + public: + task_cleanup(task_io_service& task_io_svc) + : task_io_service_(task_io_svc) + { + } + + ~task_cleanup() + { + // Reinsert the task at the end of the handler queue. + boost::asio::detail::mutex::scoped_lock back_lock( + task_io_service_.back_mutex_); + task_io_service_.back_task_thread_ = 0; + task_io_service_.handler_queue_.push(&task_io_service_.task_handler_); + } + + private: + task_io_service& task_io_service_; + }; + + // Helper class to perform handler-related operations on block exit. + class handler_cleanup + { + public: + handler_cleanup(task_io_service& task_io_svc) + : task_io_service_(task_io_svc) + { + } + + ~handler_cleanup() + { + task_io_service_.work_finished(); + } + + private: + task_io_service& task_io_service_; + }; + + // Mutexes to protect access to internal data. + boost::asio::detail::mutex front_mutex_; + boost::asio::detail::mutex back_mutex_; + + // The task to be run by this service. + Task* task_; + + // Handler object to represent the position of the task in the queue. + class task_handler + : public handler_queue::handler + { + public: + task_handler() + : handler_queue::handler(0, 0) + { + } + } task_handler_; + + // The count of unfinished work. + boost::detail::atomic_count outstanding_work_; + + // The queue of handlers that are ready to be delivered. + handler_queue handler_queue_; + + // Flag to indicate that the dispatcher has been stopped. + bool front_stopped_; + bool back_stopped_; + + // Flag to indicate that the dispatcher has been shut down. + bool back_shutdown_; + + // Structure containing information about an idle thread. + struct idle_thread_info + { + event wakeup_event; + idle_thread_info* next; + }; + + // The number of threads that are currently idle. + idle_thread_info* back_first_idle_thread_; + + // The thread that is currently blocked on the task. + idle_thread_info* back_task_thread_; +}; + +} // namespace detail +} // namespace asio +} // namespace boost + +#include <boost/asio/detail/pop_options.hpp> + +#endif // BOOST_ASIO_DETAIL_TASK_IO_SERVICE_2LOCK_HPP |