epoll_reactor.hpp

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//
// epoll_reactor.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_EPOLL_REACTOR_HPP
#define BOOST_ASIO_DETAIL_EPOLL_REACTOR_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/detail/epoll_reactor_fwd.hpp>

#if defined(BOOST_ASIO_HAS_EPOLL)

#include <boost/asio/detail/push_options.hpp>
#include <cstddef>
#include <vector>
#include <sys/epoll.h>
#include <boost/config.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/throw_exception.hpp>
#include <boost/system/system_error.hpp>
#include <boost/asio/detail/pop_options.hpp>

#include <boost/asio/error.hpp>
#include <boost/asio/io_service.hpp>
#include <boost/asio/detail/bind_handler.hpp>
#include <boost/asio/detail/hash_map.hpp>
#include <boost/asio/detail/mutex.hpp>
#include <boost/asio/detail/task_io_service.hpp>
#include <boost/asio/detail/thread.hpp>
#include <boost/asio/detail/reactor_op_queue.hpp>
#include <boost/asio/detail/select_interrupter.hpp>
#include <boost/asio/detail/service_base.hpp>
#include <boost/asio/detail/signal_blocker.hpp>
#include <boost/asio/detail/socket_types.hpp>
#include <boost/asio/detail/timer_queue.hpp>

namespace boost {
namespace asio {
namespace detail {

template <bool Own_Thread>
class epoll_reactor
  : public boost::asio::detail::service_base<epoll_reactor<Own_Thread> >
{
public:
  // Per-descriptor data.
  struct per_descriptor_data
  {
    bool allow_speculative_read;
    bool allow_speculative_write;
  };

  // Constructor.
  epoll_reactor(boost::asio::io_service& io_service)
    : boost::asio::detail::service_base<epoll_reactor<Own_Thread> >(io_service),
      mutex_(),
      epoll_fd_(do_epoll_create()),
      wait_in_progress_(false),
      interrupter_(),
      read_op_queue_(),
      write_op_queue_(),
      except_op_queue_(),
      pending_cancellations_(),
      stop_thread_(false),
      thread_(0),
      shutdown_(false),
      need_epoll_wait_(true)
  {
    // Start the reactor's internal thread only if needed.
    if (Own_Thread)
    {
      boost::asio::detail::signal_blocker sb;
      thread_ = new boost::asio::detail::thread(
          bind_handler(&epoll_reactor::call_run_thread, this));
    }

    // Add the interrupter's descriptor to epoll.
    epoll_event ev = { 0, { 0 } };
    ev.events = EPOLLIN | EPOLLERR;
    ev.data.fd = interrupter_.read_descriptor();
    epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, interrupter_.read_descriptor(), &ev);
  }

  // Destructor.
  ~epoll_reactor()
  {
    shutdown_service();
    close(epoll_fd_);
  }

  // Destroy all user-defined handler objects owned by the service.
  void shutdown_service()
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    shutdown_ = true;
    stop_thread_ = true;
    lock.unlock();

    if (thread_)
    {
      interrupter_.interrupt();
      thread_->join();
      delete thread_;
      thread_ = 0;
    }

    read_op_queue_.destroy_operations();
    write_op_queue_.destroy_operations();
    except_op_queue_.destroy_operations();

    for (std::size_t i = 0; i < timer_queues_.size(); ++i)
      timer_queues_[i]->destroy_timers();
    timer_queues_.clear();
  }

  // Initialise the task, but only if the reactor is not in its own thread.
  void init_task()
  {
    if (!Own_Thread)
    {
      typedef task_io_service<epoll_reactor<Own_Thread> > task_io_service_type;
      use_service<task_io_service_type>(this->get_io_service()).init_task();
    }
  }

  // Register a socket with the reactor. Returns 0 on success, system error
  // code on failure.
  int register_descriptor(socket_type descriptor,
      per_descriptor_data& descriptor_data)
  {
    // No need to lock according to epoll documentation.

    descriptor_data.allow_speculative_read = true;
    descriptor_data.allow_speculative_write = true;

    epoll_event ev = { 0, { 0 } };
    ev.events = 0;
    ev.data.fd = descriptor;
    int result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
    if (result != 0)
      return errno;
    return 0;
  }

  // Start a new read operation. The handler object will be invoked when the
  // given descriptor is ready to be read, or an error has occurred.
  template <typename Handler>
  void start_read_op(socket_type descriptor,
      per_descriptor_data& descriptor_data,
      Handler handler, bool allow_speculative_read = true)
  {
    if (allow_speculative_read && descriptor_data.allow_speculative_read)
    {
      boost::system::error_code ec;
      std::size_t bytes_transferred = 0;
      if (handler.perform(ec, bytes_transferred))
      {
        handler.complete(ec, bytes_transferred);
        return;
      }

      // We only get one shot at a speculative read in this function.
      allow_speculative_read = false;
    }

    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (!allow_speculative_read)
      need_epoll_wait_ = true;
    else if (!read_op_queue_.has_operation(descriptor))
    {
      // Speculative reads are ok as there are no queued read operations.
      descriptor_data.allow_speculative_read = true;

      boost::system::error_code ec;
      std::size_t bytes_transferred = 0;
      if (handler.perform(ec, bytes_transferred))
      {
        handler.complete(ec, bytes_transferred);
        return;
      }
    }

    // Speculative reads are not ok as there will be queued read operations.
    descriptor_data.allow_speculative_read = false;

    if (read_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLIN | EPOLLERR | EPOLLHUP;
      if (write_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLOUT;
      if (except_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLPRI;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0 && errno == ENOENT)
        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
      if (result != 0)
      {
        boost::system::error_code ec(errno,
            boost::asio::error::get_system_category());
        read_op_queue_.perform_all_operations(descriptor, ec);
      }
    }
  }

  // Start a new write operation. The handler object will be invoked when the
  // given descriptor is ready to be written, or an error has occurred.
  template <typename Handler>
  void start_write_op(socket_type descriptor,
      per_descriptor_data& descriptor_data,
      Handler handler, bool allow_speculative_write = true)
  {
    if (allow_speculative_write && descriptor_data.allow_speculative_write)
    {
      boost::system::error_code ec;
      std::size_t bytes_transferred = 0;
      if (handler.perform(ec, bytes_transferred))
      {
        handler.complete(ec, bytes_transferred);
        return;
      }

      // We only get one shot at a speculative write in this function.
      allow_speculative_write = false;
    }

    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (!allow_speculative_write)
      need_epoll_wait_ = true;
    else if (!write_op_queue_.has_operation(descriptor))
    {
      // Speculative writes are ok as there are no queued write operations.
      descriptor_data.allow_speculative_write = true;

      boost::system::error_code ec;
      std::size_t bytes_transferred = 0;
      if (handler.perform(ec, bytes_transferred))
      {
        handler.complete(ec, bytes_transferred);
        return;
      }
    }

    // Speculative writes are not ok as there will be queued write operations.
    descriptor_data.allow_speculative_write = false;

    if (write_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLOUT | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      if (except_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLPRI;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0 && errno == ENOENT)
        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
      if (result != 0)
      {
        boost::system::error_code ec(errno,
            boost::asio::error::get_system_category());
        write_op_queue_.perform_all_operations(descriptor, ec);
      }
    }
  }

  // Start a new exception operation. The handler object will be invoked when
  // the given descriptor has exception information, or an error has occurred.
  template <typename Handler>
  void start_except_op(socket_type descriptor,
      per_descriptor_data&, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (except_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLPRI | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      if (write_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLOUT;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0 && errno == ENOENT)
        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
      if (result != 0)
      {
        boost::system::error_code ec(errno,
            boost::asio::error::get_system_category());
        except_op_queue_.perform_all_operations(descriptor, ec);
      }
    }
  }

  // Start a new write operation. The handler object will be invoked when the
  // given descriptor is ready for writing or an error has occurred. Speculative
  // writes are not allowed.
  template <typename Handler>
  void start_connect_op(socket_type descriptor,
      per_descriptor_data& descriptor_data, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    // Speculative writes are not ok as there will be queued write operations.
    descriptor_data.allow_speculative_write = false;

    if (write_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLOUT | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      if (except_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLPRI;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0 && errno == ENOENT)
        result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
      if (result != 0)
      {
        boost::system::error_code ec(errno,
            boost::asio::error::get_system_category());
        write_op_queue_.perform_all_operations(descriptor, ec);
      }
    }
  }

  // Cancel all operations associated with the given descriptor. The
  // handlers associated with the descriptor will be invoked with the
  // operation_aborted error.
  void cancel_ops(socket_type descriptor, per_descriptor_data&)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    cancel_ops_unlocked(descriptor);
  }