dev_poll_reactor.hpp 13.8 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
//
// dev_poll_reactor.hpp
// ~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2010 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 ASIO_DETAIL_DEV_POLL_REACTOR_HPP
#define ASIO_DETAIL_DEV_POLL_REACTOR_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/push_options.hpp"

#include "asio/detail/dev_poll_reactor_fwd.hpp"

#if defined(ASIO_HAS_DEV_POLL)

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

#include "asio/error.hpp"
#include "asio/io_service.hpp"
#include "asio/system_error.hpp"
#include "asio/detail/hash_map.hpp"
#include "asio/detail/mutex.hpp"
#include "asio/detail/op_queue.hpp"
#include "asio/detail/reactor_op.hpp"
#include "asio/detail/reactor_op_queue.hpp"
#include "asio/detail/select_interrupter.hpp"
#include "asio/detail/service_base.hpp"
#include "asio/detail/socket_types.hpp"
#include "asio/detail/timer_op.hpp"
#include "asio/detail/timer_queue_base.hpp"
#include "asio/detail/timer_queue_fwd.hpp"
#include "asio/detail/timer_queue_set.hpp"

namespace asio {
namespace detail {

class dev_poll_reactor
  : public asio::detail::service_base<dev_poll_reactor>
{
public:
  enum { read_op = 0, write_op = 1,
    connect_op = 1, except_op = 2, max_ops = 3 };

  // Per-descriptor data.
  struct per_descriptor_data
  {
  };

  // Constructor.
  dev_poll_reactor(asio::io_service& io_service)
    : asio::detail::service_base<dev_poll_reactor>(io_service),
      io_service_(use_service<io_service_impl>(io_service)),
      mutex_(),
      dev_poll_fd_(do_dev_poll_create()),
      interrupter_(),
      shutdown_(false)
  {
    // Add the interrupter's descriptor to /dev/poll.
    ::pollfd ev = { 0 };
    ev.fd = interrupter_.read_descriptor();
    ev.events = POLLIN | POLLERR;
    ev.revents = 0;
    ::write(dev_poll_fd_, &ev, sizeof(ev));
  }

  // Destructor.
  ~dev_poll_reactor()
  {
    shutdown_service();
    ::close(dev_poll_fd_);
  }

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

    op_queue<operation> ops;

    for (int i = 0; i < max_ops; ++i)
      op_queue_[i].get_all_operations(ops);

    timer_queues_.get_all_timers(ops);
  } 

  // Initialise the task.
  void init_task()
  {
    io_service_.init_task();
  }

  // Register a socket with the reactor. Returns 0 on success, system error
  // code on failure.
  int register_descriptor(socket_type, per_descriptor_data&)
  {
    return 0;
  }

  // Start a new operation. The reactor operation will be performed when the
  // given descriptor is flagged as ready, or an error has occurred.
  void start_op(int op_type, socket_type descriptor,
      per_descriptor_data&, reactor_op* op, bool allow_speculative)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (allow_speculative)
    {
      if (op_type != read_op || !op_queue_[except_op].has_operation(descriptor))
      {
        if (!op_queue_[op_type].has_operation(descriptor))
        {
          if (op->perform())
          {
            lock.unlock();
            io_service_.post_immediate_completion(op);
            return;
          }
        }
      }
    }

    bool first = op_queue_[op_type].enqueue_operation(descriptor, op);
    io_service_.work_started();
    if (first)
    {
      ::pollfd& ev = add_pending_event_change(descriptor);
      ev.events = POLLERR | POLLHUP;
      if (op_type == read_op
          || op_queue_[read_op].has_operation(descriptor))
        ev.events |= POLLIN;
      if (op_type == write_op
          || op_queue_[write_op].has_operation(descriptor))
        ev.events |= POLLOUT;
      if (op_type == except_op
          || op_queue_[except_op].has_operation(descriptor))
        ev.events |= POLLPRI;
      interrupter_.interrupt();
    }
  }

  // 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&)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);
    cancel_ops_unlocked(descriptor, asio::error::operation_aborted);
  }

  // Cancel any operations that are running against the descriptor and remove
  // its registration from the reactor.
  void close_descriptor(socket_type descriptor, per_descriptor_data&)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);

    // Remove the descriptor from /dev/poll.
    ::pollfd& ev = add_pending_event_change(descriptor);
    ev.events = POLLREMOVE;
    interrupter_.interrupt();

    // Cancel any outstanding operations associated with the descriptor.
    cancel_ops_unlocked(descriptor, asio::error::operation_aborted);
  }

  // Add a new timer queue to the reactor.
  template <typename Time_Traits>
  void add_timer_queue(timer_queue<Time_Traits>& timer_queue)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);
    timer_queues_.insert(&timer_queue);
  }

  // Remove a timer queue from the reactor.
  template <typename Time_Traits>
  void remove_timer_queue(timer_queue<Time_Traits>& timer_queue)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);
    timer_queues_.erase(&timer_queue);
  }

  // Schedule a new operation in the given timer queue to expire at the
  // specified absolute time.
  template <typename Time_Traits>
  void schedule_timer(timer_queue<Time_Traits>& timer_queue,
      const typename Time_Traits::time_type& time, timer_op* op, void* token)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);
    if (!shutdown_)
    {
      bool earliest = timer_queue.enqueue_timer(time, op, token);
      io_service_.work_started();
      if (earliest)
        interrupter_.interrupt();
    }
  }

  // Cancel the timer operations associated with the given token. Returns the
  // number of operations that have been posted or dispatched.
  template <typename Time_Traits>
  std::size_t cancel_timer(timer_queue<Time_Traits>& timer_queue, void* token)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);
    op_queue<operation> ops;
    std::size_t n = timer_queue.cancel_timer(token, ops);
    lock.unlock();
    io_service_.post_deferred_completions(ops);
    return n;
  }

  // Run /dev/poll once until interrupted or events are ready to be dispatched.
  void run(bool block, op_queue<operation>& ops)
  {
    asio::detail::mutex::scoped_lock lock(mutex_);

    // We can return immediately if there's no work to do and the reactor is
    // not supposed to block.
    if (!block && op_queue_[read_op].empty() && op_queue_[write_op].empty()
        && op_queue_[except_op].empty() && timer_queues_.all_empty())
      return;

    // Write the pending event registration changes to the /dev/poll descriptor.
    std::size_t events_size = sizeof(::pollfd) * pending_event_changes_.size();
    if (events_size > 0)
    {
      errno = 0;
      int result = ::write(dev_poll_fd_,
          &pending_event_changes_[0], events_size);
      if (result != static_cast<int>(events_size))
      {
        asio::error_code ec = asio::error_code(
            errno, asio::error::get_system_category());
        for (std::size_t i = 0; i < pending_event_changes_.size(); ++i)
        {
          int descriptor = pending_event_changes_[i].fd;
          for (int j = 0; j < max_ops; ++j)
            op_queue_[j].cancel_operations(descriptor, ops, ec);
        }
      }
      pending_event_changes_.clear();
      pending_event_change_index_.clear();
    }

    int timeout = block ? get_timeout() : 0;
    lock.unlock();

    // Block on the /dev/poll descriptor.
    ::pollfd events[128] = { { 0 } };
    ::dvpoll dp = { 0 };
    dp.dp_fds = events;
    dp.dp_nfds = 128;
    dp.dp_timeout = timeout;
    int num_events = ::ioctl(dev_poll_fd_, DP_POLL, &dp);

    lock.lock();

    // Dispatch the waiting events.
    for (int i = 0; i < num_events; ++i)
    {
      int descriptor = events[i].fd;
      if (descriptor == interrupter_.read_descriptor())
      {
        interrupter_.reset();
      }
      else
      {
        bool more_reads = false;
        bool more_writes = false;
        bool more_except = false;

        // Exception operations must be processed first to ensure that any
        // out-of-band data is read before normal data.
        if (events[i].events & (POLLPRI | POLLERR | POLLHUP))
          more_except =
            op_queue_[except_op].perform_operations(descriptor, ops);
        else
          more_except = op_queue_[except_op].has_operation(descriptor);

        if (events[i].events & (POLLIN | POLLERR | POLLHUP))
          more_reads = op_queue_[read_op].perform_operations(descriptor, ops);
        else
          more_reads = op_queue_[read_op].has_operation(descriptor);

        if (events[i].events & (POLLOUT | POLLERR | POLLHUP))
          more_writes = op_queue_[write_op].perform_operations(descriptor, ops);
        else
          more_writes = op_queue_[write_op].has_operation(descriptor);

        if ((events[i].events & (POLLERR | POLLHUP)) != 0
              && !more_except && !more_reads && !more_writes)
        {
          // If we have an event and no operations associated with the
          // descriptor then we need to delete the descriptor from /dev/poll.
          // The poll operation can produce POLLHUP or POLLERR events when there
          // is no operation pending, so if we do not remove the descriptor we
          // can end up in a tight polling loop.
          ::pollfd ev = { 0 };
          ev.fd = descriptor;
          ev.events = POLLREMOVE;
          ev.revents = 0;
          ::write(dev_poll_fd_, &ev, sizeof(ev));
        }
        else
        {
          ::pollfd ev = { 0 };
          ev.fd = descriptor;
          ev.events = POLLERR | POLLHUP;
          if (more_reads)
            ev.events |= POLLIN;
          if (more_writes)
            ev.events |= POLLOUT;
          if (more_except)
            ev.events |= POLLPRI;
          ev.revents = 0;
          int result = ::write(dev_poll_fd_, &ev, sizeof(ev));
          if (result != sizeof(ev))
          {
            asio::error_code ec(errno,
                asio::error::get_system_category());
            for (int j = 0; j < max_ops; ++j)
              op_queue_[j].cancel_operations(descriptor, ops, ec);
          }
        }
      }
    }
    timer_queues_.get_ready_timers(ops);
  }

  // Interrupt the select loop.
  void interrupt()
  {
    interrupter_.interrupt();
  }

private:
  // Create the /dev/poll file descriptor. Throws an exception if the descriptor
  // cannot be created.
  static int do_dev_poll_create()
  {
    int fd = ::open("/dev/poll", O_RDWR);
    if (fd == -1)
    {
      boost::throw_exception(
          asio::system_error(
            asio::error_code(errno,
              asio::error::get_system_category()),
            "/dev/poll"));
    }
    return fd;
  }

  // Get the timeout value for the /dev/poll DP_POLL operation. The timeout
  // value is returned as a number of milliseconds. A return value of -1
  // indicates that the poll should block indefinitely.
  int get_timeout()
  {
    // By default we will wait no longer than 5 minutes. This will ensure that
    // any changes to the system clock are detected after no longer than this.
    return timer_queues_.wait_duration_msec(5 * 60 * 1000);
  }

  // Cancel all operations associated with the given descriptor. The do_cancel
  // function of the handler objects will be invoked. This function does not
  // acquire the dev_poll_reactor's mutex.
  void cancel_ops_unlocked(socket_type descriptor,
      const asio::error_code& ec)
  {
    bool need_interrupt = false;
    op_queue<operation> ops;
    for (int i = 0; i < max_ops; ++i)
      need_interrupt = op_queue_[i].cancel_operations(
          descriptor, ops, ec) || need_interrupt;
    io_service_.post_deferred_completions(ops);
    if (need_interrupt)
      interrupter_.interrupt();
  }

  // Add a pending event entry for the given descriptor.
  ::pollfd& add_pending_event_change(int descriptor)
  {
    hash_map<int, std::size_t>::iterator iter
      = pending_event_change_index_.find(descriptor);
    if (iter == pending_event_change_index_.end())
    {
      std::size_t index = pending_event_changes_.size();
      pending_event_changes_.reserve(pending_event_changes_.size() + 1);
      pending_event_change_index_.insert(std::make_pair(descriptor, index));
      pending_event_changes_.push_back(::pollfd());
      pending_event_changes_[index].fd = descriptor;
      pending_event_changes_[index].revents = 0;
      return pending_event_changes_[index];
    }
    else
    {
      return pending_event_changes_[iter->second];
    }
  }

  // The io_service implementation used to post completions.
  io_service_impl& io_service_;

  // Mutex to protect access to internal data.
  asio::detail::mutex mutex_;

  // The /dev/poll file descriptor.
  int dev_poll_fd_;

  // Vector of /dev/poll events waiting to be written to the descriptor.
  std::vector< ::pollfd> pending_event_changes_;

  // Hash map to associate a descriptor with a pending event change index.
  hash_map<int, std::size_t> pending_event_change_index_;

  // The interrupter is used to break a blocking DP_POLL operation.
  select_interrupter interrupter_;

  // The queues of read, write and except operations.
  reactor_op_queue<socket_type> op_queue_[max_ops];

  // The timer queues.
  timer_queue_set timer_queues_;

  // Whether the service has been shut down.
  bool shutdown_;
};

} // namespace detail
} // namespace asio

#endif // defined(ASIO_HAS_DEV_POLL)

#include "asio/detail/pop_options.hpp"

#endif // ASIO_DETAIL_DEV_POLL_REACTOR_HPP