Root/libs / corosio / src / corosio / src / detail / select / scheduler.cpp
Prev Index Next

libs/corosio/src/corosio/src/detail/select/scheduler.cpp

73.4% Lines (268/365) 87.9% Functions (29/33) 62.2% Branches (166/267)
libs/corosio/src/corosio/src/detail/select/scheduler.cpp
Line Branch Hits Source Code
1 //
2 // Copyright (c) 2026 Steve Gerbino
3 //
4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 //
7 // Official repository: https://github.com/cppalliance/corosio
8 //
9
10 #include <boost/corosio/detail/platform.hpp>
11
12 #if BOOST_COROSIO_HAS_SELECT
13
14 #include "src/detail/select/scheduler.hpp"
15 #include "src/detail/select/op.hpp"
16 #include "src/detail/make_err.hpp"
17 #include "src/detail/posix/resolver_service.hpp"
18 #include "src/detail/posix/signals.hpp"
19
20 #include <boost/corosio/detail/except.hpp>
21 #include <boost/corosio/detail/thread_local_ptr.hpp>
22
23 #include <chrono>
24 #include <limits>
25
26 #include <errno.h>
27 #include <fcntl.h>
28 #include <sys/select.h>
29 #include <sys/socket.h>
30 #include <unistd.h>
31
32 /*
33 select Scheduler - Single Reactor Model
34 =======================================
35
36 This scheduler mirrors the epoll_scheduler design but uses select() instead
37 of epoll for I/O multiplexing. The thread coordination strategy is identical:
38 one thread becomes the "reactor" while others wait on a condition variable.
39
40 Thread Model
41 ------------
42 - ONE thread runs select() at a time (the reactor thread)
43 - OTHER threads wait on wakeup_event_ (condition variable) for handlers
44 - When work is posted, exactly one waiting thread wakes via notify_one()
45
46 Key Differences from epoll
47 --------------------------
48 - Uses self-pipe instead of eventfd for interruption (more portable)
49 - fd_set rebuilding each iteration (O(n) vs O(1) for epoll)
50 - FD_SETSIZE limit (~1024 fds on most systems)
51 - Level-triggered only (no edge-triggered mode)
52
53 Self-Pipe Pattern
54 -----------------
55 To interrupt a blocking select() call (e.g., when work is posted or a timer
56 expires), we write a byte to pipe_fds_[1]. The read end pipe_fds_[0] is
57 always in the read_fds set, so select() returns immediately. We drain the
58 pipe to clear the readable state.
59
60 fd-to-op Mapping
61 ----------------
62 We use an unordered_map<int, fd_state> to track which operations are
63 registered for each fd. This allows O(1) lookup when select() returns
64 ready fds. Each fd can have at most one read op and one write op registered.
65 */
66
67 namespace boost::corosio::detail {
68
69 namespace {
70
71 struct scheduler_context
72 {
73 select_scheduler const* key;
74 scheduler_context* next;
75 };
76
77 corosio::detail::thread_local_ptr<scheduler_context> context_stack;
78
79 struct thread_context_guard
80 {
81 scheduler_context frame_;
82
83 95 explicit thread_context_guard(
84 select_scheduler const* ctx) noexcept
85 95 : frame_{ctx, context_stack.get()}
86 {
87 95 context_stack.set(&frame_);
88 95 }
89
90 95 ~thread_context_guard() noexcept
91 {
92 95 context_stack.set(frame_.next);
93 95 }
94 };
95
96 } // namespace
97
98 120 select_scheduler::
99 select_scheduler(
100 capy::execution_context& ctx,
101 120 int)
102 120 : pipe_fds_{-1, -1}
103 120 , outstanding_work_(0)
104 120 , stopped_(false)
105 120 , shutdown_(false)
106 120 , max_fd_(-1)
107 120 , reactor_running_(false)
108 120 , reactor_interrupted_(false)
109 240 , idle_thread_count_(0)
110 {
111 // Create self-pipe for interrupting select()
112
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 120 times.
 120 if (::pipe(pipe_fds_) < 0)
113 ✗ detail::throw_system_error(make_err(errno), "pipe");
114
115 // Set both ends to non-blocking and close-on-exec
116
2/2
✓ Branch 0 taken 240 times.
✓ Branch 1 taken 120 times.
 360 for (int i = 0; i < 2; ++i)
117 {
118
1/1
✓ Branch 1 taken 240 times.
 240 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
119
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 240 times.
 240 if (flags == -1)
120 {
121 ✗ int errn = errno;
122 ✗ ::close(pipe_fds_[0]);
123 ✗ ::close(pipe_fds_[1]);
124 ✗ detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
125 }
126
2/3
✓ Branch 1 taken 240 times.
✗ Branch 3 not taken.
✓ Branch 4 taken 240 times.
 240 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
127 {
128 ✗ int errn = errno;
129 ✗ ::close(pipe_fds_[0]);
130 ✗ ::close(pipe_fds_[1]);
131 ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
132 }
133
2/3
✓ Branch 1 taken 240 times.
✗ Branch 3 not taken.
✓ Branch 4 taken 240 times.
 240 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
134 {
135 ✗ int errn = errno;
136 ✗ ::close(pipe_fds_[0]);
137 ✗ ::close(pipe_fds_[1]);
138 ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
139 }
140 }
141
142
1/1
✓ Branch 1 taken 120 times.
 120 timer_svc_ = &get_timer_service(ctx, *this);
143
1/1
✓ Branch 3 taken 120 times.
 120 timer_svc_->set_on_earliest_changed(
144 timer_service::callback(
145 this,
146 4082 [](void* p) { static_cast<select_scheduler*>(p)->interrupt_reactor(); }));
147
148 // Initialize resolver service
149
1/1
✓ Branch 1 taken 120 times.
 120 get_resolver_service(ctx, *this);
150
151 // Initialize signal service
152
1/1
✓ Branch 1 taken 120 times.
 120 get_signal_service(ctx, *this);
153
154 // Push task sentinel to interleave reactor runs with handler execution
155 120 completed_ops_.push(&task_op_);
156 120 }
157
158 240 select_scheduler::
159 120 ~select_scheduler()
160 {
161
1/2
✓ Branch 0 taken 120 times.
✗ Branch 1 not taken.
 120 if (pipe_fds_[0] >= 0)
162 120 ::close(pipe_fds_[0]);
163
1/2
✓ Branch 0 taken 120 times.
✗ Branch 1 not taken.
 120 if (pipe_fds_[1] >= 0)
164 120 ::close(pipe_fds_[1]);
165 240 }
166
167 void
168 120 select_scheduler::
169 shutdown()
170 {
171 {
172
1/1
✓ Branch 1 taken 120 times.
 120 std::unique_lock lock(mutex_);
173 120 shutdown_ = true;
174
175
2/2
✓ Branch 1 taken 120 times.
✓ Branch 2 taken 120 times.
 240 while (auto* h = completed_ops_.pop())
176 {
177
1/2
✓ Branch 0 taken 120 times.
✗ Branch 1 not taken.
 120 if (h == &task_op_)
178 120 continue;
179 ✗ lock.unlock();
180 ✗ h->destroy();
181 ✗ lock.lock();
182 120 }
183 120 }
184
185 120 outstanding_work_.store(0, std::memory_order_release);
186
187
1/2
✓ Branch 0 taken 120 times.
✗ Branch 1 not taken.
 120 if (pipe_fds_[1] >= 0)
188 120 interrupt_reactor();
189
190 120 wakeup_event_.notify_all();
191 120 }
192
193 void
194 4242 select_scheduler::
195 post(capy::coro h) const
196 {
197 struct post_handler final
198 : scheduler_op
199 {
200 capy::coro h_;
201
202 explicit
203 4242 post_handler(capy::coro h)
204 4242 : h_(h)
205 {
206 4242 }
207
208 8484 ~post_handler() = default;
209
210 4242 void operator()() override
211 {
212 4242 auto h = h_;
213
1/2
✓ Branch 0 taken 4242 times.
✗ Branch 1 not taken.
 4242 delete this;
214
1/1
✓ Branch 1 taken 4242 times.
 4242 h.resume();
215 4242 }
216
217 ✗ void destroy() override
218 {
219 ✗ delete this;
220 ✗ }
221 };
222
223
1/1
✓ Branch 1 taken 4242 times.
 4242 auto ph = std::make_unique<post_handler>(h);
224 4242 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
225
226
1/1
✓ Branch 1 taken 4242 times.
 4242 std::unique_lock lock(mutex_);
227 4242 completed_ops_.push(ph.release());
228
1/1
✓ Branch 1 taken 4242 times.
 4242 wake_one_thread_and_unlock(lock);
229 4242 }
230
231 void
232 236528 select_scheduler::
233 post(scheduler_op* h) const
234 {
235 236528 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
236
237
1/1
✓ Branch 1 taken 236528 times.
 236528 std::unique_lock lock(mutex_);
238 236528 completed_ops_.push(h);
239
1/1
✓ Branch 1 taken 236528 times.
 236528 wake_one_thread_and_unlock(lock);
240 236528 }
241
242 void
243 4079 select_scheduler::
244 on_work_started() noexcept
245 {
246 4079 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
247 4079 }
248
249 void
250 4073 select_scheduler::
251 on_work_finished() noexcept
252 {
253
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 4073 times.
 8146 if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
254 ✗ stop();
255 4073 }
256
257 bool
258 240595 select_scheduler::
259 running_in_this_thread() const noexcept
260 {
261
2/2
✓ Branch 1 taken 240440 times.
✓ Branch 2 taken 155 times.
 240595 for (auto* c = context_stack.get(); c != nullptr; c = c->next)
262
1/2
✓ Branch 0 taken 240440 times.
✗ Branch 1 not taken.
 240440 if (c->key == this)
263 240440 return true;
264 155 return false;
265 }
266
267 void
268 1 select_scheduler::
269 stop()
270 {
271 1 bool expected = false;
272
1/2
✓ Branch 1 taken 1 time.
✗ Branch 2 not taken.
 1 if (stopped_.compare_exchange_strong(expected, true,
273 std::memory_order_release, std::memory_order_relaxed))
274 {
275 // Wake all threads so they notice stopped_ and exit
276 {
277
1/1
✓ Branch 1 taken 1 time.
 1 std::lock_guard lock(mutex_);
278 1 wakeup_event_.notify_all();
279 1 }
280
1/1
✓ Branch 1 taken 1 time.
 1 interrupt_reactor();
281 }
282 1 }
283
284 bool
285 1 select_scheduler::
286 stopped() const noexcept
287 {
288 1 return stopped_.load(std::memory_order_acquire);
289 }
290
291 void
292 34 select_scheduler::
293 restart()
294 {
295 34 stopped_.store(false, std::memory_order_release);
296 34 }
297
298 std::size_t
299 89 select_scheduler::
300 run()
301 {
302
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 89 times.
 89 if (stopped_.load(std::memory_order_acquire))
303 ✗ return 0;
304
305
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 89 times.
 178 if (outstanding_work_.load(std::memory_order_acquire) == 0)
306 {
307 ✗ stop();
308 ✗ return 0;
309 }
310
311 89 thread_context_guard ctx(this);
312
313 89 std::size_t n = 0;
314
3/3
✓ Branch 1 taken 248601 times.
✓ Branch 3 taken 248512 times.
✓ Branch 4 taken 89 times.
 248601 while (do_one(-1))
315
1/2
✓ Branch 1 taken 248512 times.
✗ Branch 2 not taken.
 248512 if (n != (std::numeric_limits<std::size_t>::max)())
316 248512 ++n;
317 89 return n;
318 89 }
319
320 std::size_t
321 ✗ select_scheduler::
322 run_one()
323 {
324 ✗ if (stopped_.load(std::memory_order_acquire))
325 ✗ return 0;
326
327 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
328 {
329 ✗ stop();
330 ✗ return 0;
331 }
332
333 ✗ thread_context_guard ctx(this);
334 ✗ return do_one(-1);
335 ✗ }
336
337 std::size_t
338 7 select_scheduler::
339 wait_one(long usec)
340 {
341
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 7 times.
 7 if (stopped_.load(std::memory_order_acquire))
342 ✗ return 0;
343
344
2/2
✓ Branch 1 taken 1 time.
✓ Branch 2 taken 6 times.
 14 if (outstanding_work_.load(std::memory_order_acquire) == 0)
345 {
346
1/1
✓ Branch 1 taken 1 time.
 1 stop();
347 1 return 0;
348 }
349
350 6 thread_context_guard ctx(this);
351
1/1
✓ Branch 1 taken 6 times.
 6 return do_one(usec);
352 6 }
353
354 std::size_t
355 ✗ select_scheduler::
356 poll()
357 {
358 ✗ if (stopped_.load(std::memory_order_acquire))
359 ✗ return 0;
360
361 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
362 {
363 ✗ stop();
364 ✗ return 0;
365 }
366
367 ✗ thread_context_guard ctx(this);
368
369 ✗ std::size_t n = 0;
370 ✗ while (do_one(0))
371 ✗ if (n != (std::numeric_limits<std::size_t>::max)())
372 ✗ ++n;
373 ✗ return n;
374 ✗ }
375
376 std::size_t
377 ✗ select_scheduler::
378 poll_one()
379 {
380 ✗ if (stopped_.load(std::memory_order_acquire))
381 ✗ return 0;
382
383 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
384 {
385 ✗ stop();
386 ✗ return 0;
387 }
388
389 ✗ thread_context_guard ctx(this);
390 ✗ return do_one(0);
391 ✗ }
392
393 void
394 7869 select_scheduler::
395 register_fd(int fd, select_op* op, int events) const
396 {
397 // Validate fd is within select() limits
398
2/4
✓ Branch 0 taken 7869 times.
✗ Branch 1 not taken.
✗ Branch 2 not taken.
✓ Branch 3 taken 7869 times.
 7869 if (fd < 0 || fd >= FD_SETSIZE)
399 ✗ detail::throw_system_error(make_err(EINVAL), "select: fd out of range");
400
401 {
402
1/1
✓ Branch 1 taken 7869 times.
 7869 std::lock_guard lock(mutex_);
403
404
1/1
✓ Branch 1 taken 7869 times.
 7869 auto& state = registered_fds_[fd];
405
2/2
✓ Branch 0 taken 4034 times.
✓ Branch 1 taken 3835 times.
 7869 if (events & event_read)
406 4034 state.read_op = op;
407
2/2
✓ Branch 0 taken 3835 times.
✓ Branch 1 taken 4034 times.
 7869 if (events & event_write)
408 3835 state.write_op = op;
409
410
2/2
✓ Branch 0 taken 186 times.
✓ Branch 1 taken 7683 times.
 7869 if (fd > max_fd_)
411 186 max_fd_ = fd;
412 7869 }
413
414 // Wake the reactor so a thread blocked in select() rebuilds its fd_sets
415 // with the newly registered fd.
416 7869 interrupt_reactor();
417 7869 }
418
419 void
420 7843 select_scheduler::
421 deregister_fd(int fd, int events) const
422 {
423
1/1
✓ Branch 1 taken 7843 times.
 7843 std::lock_guard lock(mutex_);
424
425
1/1
✓ Branch 1 taken 7843 times.
 7843 auto it = registered_fds_.find(fd);
426
2/2
✓ Branch 2 taken 7722 times.
✓ Branch 3 taken 121 times.
 7843 if (it == registered_fds_.end())
427 7722 return;
428
429
1/2
✓ Branch 0 taken 121 times.
✗ Branch 1 not taken.
 121 if (events & event_read)
430 121 it->second.read_op = nullptr;
431
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 121 times.
 121 if (events & event_write)
432 ✗ it->second.write_op = nullptr;
433
434 // Remove entry if both are null
435
3/6
✓ Branch 1 taken 121 times.
✗ Branch 2 not taken.
✓ Branch 4 taken 121 times.
✗ Branch 5 not taken.
✓ Branch 6 taken 121 times.
✗ Branch 7 not taken.
 121 if (!it->second.read_op && !it->second.write_op)
436 {
437
1/1
✓ Branch 1 taken 121 times.
 121 registered_fds_.erase(it);
438
439 // Recalculate max_fd_ if needed
440
2/2
✓ Branch 0 taken 120 times.
✓ Branch 1 taken 1 time.
 121 if (fd == max_fd_)
441 {
442 120 max_fd_ = pipe_fds_[0]; // At minimum, the pipe read end
443
1/2
✗ Branch 7 not taken.
✓ Branch 8 taken 120 times.
 120 for (auto& [registered_fd, state] : registered_fds_)
444 {
445 ✗ if (registered_fd > max_fd_)
446 ✗ max_fd_ = registered_fd;
447 }
448 }
449 }
450 7843 }
451
452 void
453 7869 select_scheduler::
454 work_started() const noexcept
455 {
456 7869 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
457 7869 }
458
459 void
460 248645 select_scheduler::
461 work_finished() const noexcept
462 {
463
2/2
✓ Branch 0 taken 90 times.
✓ Branch 1 taken 248555 times.
 497290 if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
464 {
465 // Last work item completed - wake all threads so they can exit.
466 90 std::unique_lock lock(mutex_);
467 90 wakeup_event_.notify_all();
468
1/4
✗ Branch 0 not taken.
✓ Branch 1 taken 90 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
 90 if (reactor_running_ && !reactor_interrupted_)
469 {
470 ✗ reactor_interrupted_ = true;
471 ✗ lock.unlock();
472 ✗ interrupt_reactor();
473 }
474 90 }
475 248645 }
476
477 void
478 16137 select_scheduler::
479 interrupt_reactor() const
480 {
481 16137 char byte = 1;
482
1/1
✓ Branch 1 taken 16137 times.
 16137 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
483 16137 }
484
485 void
486 240770 select_scheduler::
487 wake_one_thread_and_unlock(std::unique_lock<std::mutex>& lock) const
488 {
489
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 240770 times.
 240770 if (idle_thread_count_ > 0)
490 {
491 // Idle worker exists - wake it via condvar
492 ✗ wakeup_event_.notify_one();
493 ✗ lock.unlock();
494 }
495
4/4
✓ Branch 0 taken 4068 times.
✓ Branch 1 taken 236702 times.
✓ Branch 2 taken 4065 times.
✓ Branch 3 taken 3 times.
 240770 else if (reactor_running_ && !reactor_interrupted_)
496 {
497 // No idle workers but reactor is running - interrupt it
498 4065 reactor_interrupted_ = true;
499 4065 lock.unlock();
500 4065 interrupt_reactor();
501 }
502 else
503 {
504 // No one to wake
505 236705 lock.unlock();
506 }
507 240770 }
508
509 struct work_guard
510 {
511 select_scheduler const* self;
512 248518 ~work_guard() { self->work_finished(); }
513 };
514
515 long
516 11766 select_scheduler::
517 calculate_timeout(long requested_timeout_us) const
518 {
519
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 11766 times.
 11766 if (requested_timeout_us == 0)
520 ✗ return 0;
521
522 11766 auto nearest = timer_svc_->nearest_expiry();
523
3/3
✓ Branch 2 taken 11766 times.
✓ Branch 4 taken 35 times.
✓ Branch 5 taken 11731 times.
 11766 if (nearest == timer_service::time_point::max())
524 35 return requested_timeout_us;
525
526 11731 auto now = std::chrono::steady_clock::now();
527
3/3
✓ Branch 1 taken 11731 times.
✓ Branch 4 taken 57 times.
✓ Branch 5 taken 11674 times.
 11731 if (nearest <= now)
528 57 return 0;
529
530
1/1
✓ Branch 1 taken 11674 times.
 11674 auto timer_timeout_us = std::chrono::duration_cast<std::chrono::microseconds>(
531
1/1
✓ Branch 1 taken 11674 times.
 23348 nearest - now).count();
532
533
1/2
✓ Branch 0 taken 11674 times.
✗ Branch 1 not taken.
 11674 if (requested_timeout_us < 0)
534 11674 return static_cast<long>(timer_timeout_us);
535
536 ✗ return static_cast<long>((std::min)(
537 ✗ static_cast<long long>(requested_timeout_us),
538 ✗ static_cast<long long>(timer_timeout_us)));
539 }
540
541 void
542 133873 select_scheduler::
543 run_reactor(std::unique_lock<std::mutex>& lock)
544 {
545 // Calculate timeout considering timers, use 0 if interrupted
546
3/3
✓ Branch 0 taken 122107 times.
✓ Branch 1 taken 11766 times.
✓ Branch 3 taken 11766 times.
 133873 long effective_timeout_us = reactor_interrupted_ ? 0 : calculate_timeout(-1);
547
548 // Build fd_sets from registered_fds_
549 fd_set read_fds, write_fds, except_fds;
550
2/2
✓ Branch 0 taken 2141968 times.
✓ Branch 1 taken 133873 times.
 2275841 FD_ZERO(&read_fds);
551
2/2
✓ Branch 0 taken 2141968 times.
✓ Branch 1 taken 133873 times.
 2275841 FD_ZERO(&write_fds);
552
2/2
✓ Branch 0 taken 2141968 times.
✓ Branch 1 taken 133873 times.
 2275841 FD_ZERO(&except_fds);
553
554 // Always include the interrupt pipe
555 133873 FD_SET(pipe_fds_[0], &read_fds);
556 133873 int nfds = pipe_fds_[0];
557
558 // Add registered fds
559
2/2
✓ Branch 7 taken 19198 times.
✓ Branch 8 taken 133873 times.
 153071 for (auto& [fd, state] : registered_fds_)
560 {
561
2/2
✓ Branch 0 taken 15363 times.
✓ Branch 1 taken 3835 times.
 19198 if (state.read_op)
562 15363 FD_SET(fd, &read_fds);
563
2/2
✓ Branch 0 taken 3835 times.
✓ Branch 1 taken 15363 times.
 19198 if (state.write_op)
564 {
565 3835 FD_SET(fd, &write_fds);
566 // Also monitor for errors on connect operations
567 3835 FD_SET(fd, &except_fds);
568 }
569
2/2
✓ Branch 0 taken 15366 times.
✓ Branch 1 taken 3832 times.
 19198 if (fd > nfds)
570 15366 nfds = fd;
571 }
572
573 // Convert timeout to timeval
574 struct timeval tv;
575 133873 struct timeval* tv_ptr = nullptr;
576
2/2
✓ Branch 0 taken 133838 times.
✓ Branch 1 taken 35 times.
 133873 if (effective_timeout_us >= 0)
577 {
578 133838 tv.tv_sec = effective_timeout_us / 1000000;
579 133838 tv.tv_usec = effective_timeout_us % 1000000;
580 133838 tv_ptr = &tv;
581 }
582
583
1/1
✓ Branch 1 taken 133873 times.
 133873 lock.unlock();
584
585
1/1
✓ Branch 1 taken 133873 times.
 133873 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
586 133873 int saved_errno = errno;
587
588 // Process timers outside the lock
589
1/1
✓ Branch 1 taken 133873 times.
 133873 timer_svc_->process_expired();
590
591
1/4
✗ Branch 0 not taken.
✓ Branch 1 taken 133873 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
 133873 if (ready < 0 && saved_errno != EINTR)
592 ✗ detail::throw_system_error(make_err(saved_errno), "select");
593
594 // Re-acquire lock before modifying completed_ops_
595
1/1
✓ Branch 1 taken 133873 times.
 133873 lock.lock();
596
597 // Drain the interrupt pipe if readable
598
3/4
✓ Branch 0 taken 12038 times.
✓ Branch 1 taken 121835 times.
✓ Branch 2 taken 12038 times.
✗ Branch 3 not taken.
 133873 if (ready > 0 && FD_ISSET(pipe_fds_[0], &read_fds))
599 {
600 char buf[256];
601
3/3
✓ Branch 1 taken 24076 times.
✓ Branch 3 taken 12038 times.
✓ Branch 4 taken 12038 times.
 24076 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) {}
602 }
603
604 // Process I/O completions
605 133873 int completions_queued = 0;
606
2/2
✓ Branch 0 taken 12038 times.
✓ Branch 1 taken 121835 times.
 133873 if (ready > 0)
607 {
608 // Iterate over registered fds (copy keys to avoid iterator invalidation)
609 12038 std::vector<int> fds_to_check;
610
1/1
✓ Branch 2 taken 12038 times.
 12038 fds_to_check.reserve(registered_fds_.size());
611
2/2
✓ Branch 7 taken 15364 times.
✓ Branch 8 taken 12038 times.
 27402 for (auto& [fd, state] : registered_fds_)
612
1/1
✓ Branch 1 taken 15364 times.
 15364 fds_to_check.push_back(fd);
613
614
2/2
✓ Branch 5 taken 15364 times.
✓ Branch 6 taken 12038 times.
 27402 for (int fd : fds_to_check)
615 {
616
1/1
✓ Branch 1 taken 15364 times.
 15364 auto it = registered_fds_.find(fd);
617
1/2
✗ Branch 2 not taken.
✓ Branch 3 taken 15364 times.
 15364 if (it == registered_fds_.end())
618 ✗ continue;
619
620 15364 auto& state = it->second;
621
622 // Check for errors (especially for connect operations)
623 15364 bool has_error = FD_ISSET(fd, &except_fds);
624
625 // Process read readiness
626
5/6
✓ Branch 0 taken 11529 times.
✓ Branch 1 taken 3835 times.
✓ Branch 2 taken 7616 times.
✓ Branch 3 taken 3913 times.
✗ Branch 4 not taken.
✓ Branch 5 taken 7616 times.
 15364 if (state.read_op && (FD_ISSET(fd, &read_fds) || has_error))
627 {
628 3913 auto* op = state.read_op;
629 // Claim the op by exchanging to unregistered. Both registering and
630 // registered states mean the op is ours to complete.
631 3913 auto prev = op->registered.exchange(
632 select_registration_state::unregistered, std::memory_order_acq_rel);
633
1/2
✓ Branch 0 taken 3913 times.
✗ Branch 1 not taken.
 3913 if (prev != select_registration_state::unregistered)
634 {
635 3913 state.read_op = nullptr;
636
637
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 3913 times.
 3913 if (has_error)
638 {
639 ✗ int errn = 0;
640 ✗ socklen_t len = sizeof(errn);
641 ✗ if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, &errn, &len) < 0)
642 ✗ errn = errno;
643 ✗ if (errn == 0)
644 ✗ errn = EIO;
645 ✗ op->complete(errn, 0);
646 }
647 else
648 {
649 3913 op->perform_io();
650 }
651
652 3913 completed_ops_.push(op);
653 3913 ++completions_queued;
654 }
655 }
656
657 // Process write readiness
658
3/6
✓ Branch 0 taken 3835 times.
✓ Branch 1 taken 11529 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 3835 times.
✗ Branch 4 not taken.
✗ Branch 5 not taken.
 15364 if (state.write_op && (FD_ISSET(fd, &write_fds) || has_error))
659 {
660 3835 auto* op = state.write_op;
661 // Claim the op by exchanging to unregistered. Both registering and
662 // registered states mean the op is ours to complete.
663 3835 auto prev = op->registered.exchange(
664 select_registration_state::unregistered, std::memory_order_acq_rel);
665
1/2
✓ Branch 0 taken 3835 times.
✗ Branch 1 not taken.
 3835 if (prev != select_registration_state::unregistered)
666 {
667 3835 state.write_op = nullptr;
668
669
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 3835 times.
 3835 if (has_error)
670 {
671 ✗ int errn = 0;
672 ✗ socklen_t len = sizeof(errn);
673 ✗ if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, &errn, &len) < 0)
674 ✗ errn = errno;
675 ✗ if (errn == 0)
676 ✗ errn = EIO;
677 ✗ op->complete(errn, 0);
678 }
679 else
680 {
681 3835 op->perform_io();
682 }
683
684 3835 completed_ops_.push(op);
685 3835 ++completions_queued;
686 }
687 }
688
689 // Clean up empty entries
690
3/4
✓ Branch 0 taken 7748 times.
✓ Branch 1 taken 7616 times.
✓ Branch 2 taken 7748 times.
✗ Branch 3 not taken.
 15364 if (!state.read_op && !state.write_op)
691
1/1
✓ Branch 1 taken 7748 times.
 7748 registered_fds_.erase(it);
692 }
693 12038 }
694
695
2/2
✓ Branch 0 taken 3916 times.
✓ Branch 1 taken 129957 times.
 133873 if (completions_queued > 0)
696 {
697
2/2
✓ Branch 0 taken 84 times.
✓ Branch 1 taken 3832 times.
 3916 if (completions_queued == 1)
698 84 wakeup_event_.notify_one();
699 else
700 3832 wakeup_event_.notify_all();
701 }
702 133873 }
703
704 std::size_t
705 248607 select_scheduler::
706 do_one(long timeout_us)
707 {
708
1/1
✓ Branch 1 taken 248607 times.
 248607 std::unique_lock lock(mutex_);
709
710 for (;;)
711 {
712
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 382480 times.
 382480 if (stopped_.load(std::memory_order_acquire))
713 ✗ return 0;
714
715 382480 scheduler_op* op = completed_ops_.pop();
716
717
2/2
✓ Branch 0 taken 133962 times.
✓ Branch 1 taken 248518 times.
 382480 if (op == &task_op_)
718 {
719 133962 bool more_handlers = !completed_ops_.empty();
720
721
2/2
✓ Branch 0 taken 11855 times.
✓ Branch 1 taken 122107 times.
 133962 if (!more_handlers)
722 {
723
2/2
✓ Branch 1 taken 89 times.
✓ Branch 2 taken 11766 times.
 23710 if (outstanding_work_.load(std::memory_order_acquire) == 0)
724 {
725 89 completed_ops_.push(&task_op_);
726 89 return 0;
727 }
728
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 11766 times.
 11766 if (timeout_us == 0)
729 {
730 ✗ completed_ops_.push(&task_op_);
731 ✗ return 0;
732 }
733 }
734
735
3/4
✓ Branch 0 taken 11766 times.
✓ Branch 1 taken 122107 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 11766 times.
 133873 reactor_interrupted_ = more_handlers || timeout_us == 0;
736 133873 reactor_running_ = true;
737
738
3/4
✓ Branch 0 taken 122107 times.
✓ Branch 1 taken 11766 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 122107 times.
 133873 if (more_handlers && idle_thread_count_ > 0)
739 ✗ wakeup_event_.notify_one();
740
741
1/1
✓ Branch 1 taken 133873 times.
 133873 run_reactor(lock);
742
743 133873 reactor_running_ = false;
744 133873 completed_ops_.push(&task_op_);
745 133873 continue;
746 133873 }
747
748
1/2
✓ Branch 0 taken 248518 times.
✗ Branch 1 not taken.
 248518 if (op != nullptr)
749 {
750
1/1
✓ Branch 1 taken 248518 times.
 248518 lock.unlock();
751 248518 work_guard g{this};
752
1/1
✓ Branch 1 taken 248518 times.
 248518 (*op)();
753 248518 return 1;
754 248518 }
755
756 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
757 ✗ return 0;
758
759 ✗ if (timeout_us == 0)
760 ✗ return 0;
761
762 ✗ ++idle_thread_count_;
763 ✗ if (timeout_us < 0)
764 ✗ wakeup_event_.wait(lock);
765 else
766 ✗ wakeup_event_.wait_for(lock, std::chrono::microseconds(timeout_us));
767 ✗ --idle_thread_count_;
768 133873 }
769 248607 }
770
771 } // namespace boost::corosio::detail
772
773 #endif // BOOST_COROSIO_HAS_SELECT
774