Index/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 2282 [](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 2581 select_scheduler::
195 post(std::coroutine_handle<> h) const
196 {
197 struct post_handler final
198 : scheduler_op
199 {
200 std::coroutine_handle<> h_;
201
202 explicit
203 2581 post_handler(std::coroutine_handle<> h)
204 2581 : h_(h)
205 {
206 2581 }
207
208 5162 ~post_handler() = default;
209
210 2581 void operator()() override
211 {
212 2581 auto h = h_;
213
1/2
✓ Branch 0 taken 2581 times.
✗ Branch 1 not taken.
 2581 delete this;
214
1/1
✓ Branch 1 taken 2581 times.
 2581 h.resume();
215 2581 }
216
217 ✗ void destroy() override
218 {
219 ✗ delete this;
220 ✗ }
221 };
222
223
1/1
✓ Branch 1 taken 2581 times.
 2581 auto ph = std::make_unique<post_handler>(h);
224 2581 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
225
226
1/1
✓ Branch 1 taken 2581 times.
 2581 std::unique_lock lock(mutex_);
227 2581 completed_ops_.push(ph.release());
228
1/1
✓ Branch 1 taken 2581 times.
 2581 wake_one_thread_and_unlock(lock);
229 2581 }
230
231 void
232 159793 select_scheduler::
233 post(scheduler_op* h) const
234 {
235 159793 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
236
237
1/1
✓ Branch 1 taken 159793 times.
 159793 std::unique_lock lock(mutex_);
238 159793 completed_ops_.push(h);
239
1/1
✓ Branch 1 taken 159793 times.
 159793 wake_one_thread_and_unlock(lock);
240 159793 }
241
242 void
243 2818 select_scheduler::
244 on_work_started() noexcept
245 {
246 2818 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
247 2818 }
248
249 void
250 2812 select_scheduler::
251 on_work_finished() noexcept
252 {
253
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2812 times.
 5624 if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
254 ✗ stop();
255 2812 }
256
257 bool
258 523 select_scheduler::
259 running_in_this_thread() const noexcept
260 {
261
2/2
✓ Branch 1 taken 368 times.
✓ Branch 2 taken 155 times.
 523 for (auto* c = context_stack.get(); c != nullptr; c = c->next)
262
1/2
✓ Branch 0 taken 368 times.
✗ Branch 1 not taken.
 368 if (c->key == this)
263 368 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 166749 times.
✓ Branch 3 taken 166660 times.
✓ Branch 4 taken 89 times.
 166749 while (do_one(-1))
315
1/2
✓ Branch 1 taken 166660 times.
✗ Branch 2 not taken.
 166660 if (n != (std::numeric_limits<std::size_t>::max)())
316 166660 ++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 4454 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 4454 times.
✗ Branch 1 not taken.
✗ Branch 2 not taken.
✓ Branch 3 taken 4454 times.
 4454 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 4454 times.
 4454 std::lock_guard lock(mutex_);
403
404
1/1
✓ Branch 1 taken 4454 times.
 4454 auto& state = registered_fds_[fd];
405
2/2
✓ Branch 0 taken 2368 times.
✓ Branch 1 taken 2086 times.
 4454 if (events & event_read)
406 2368 state.read_op = op;
407
2/2
✓ Branch 0 taken 2086 times.
✓ Branch 1 taken 2368 times.
 4454 if (events & event_write)
408 2086 state.write_op = op;
409
410
2/2
✓ Branch 0 taken 227 times.
✓ Branch 1 taken 4227 times.
 4454 if (fd > max_fd_)
411 227 max_fd_ = fd;
412 4454 }
413
414 // Wake the reactor so a thread blocked in select() rebuilds its fd_sets
415 // with the newly registered fd.
416 4454 interrupt_reactor();
417 4454 }
418
419 void
420 4386 select_scheduler::
421 deregister_fd(int fd, int events) const
422 {
423
1/1
✓ Branch 1 taken 4386 times.
 4386 std::lock_guard lock(mutex_);
424
425
1/1
✓ Branch 1 taken 4386 times.
 4386 auto it = registered_fds_.find(fd);
426
2/2
✓ Branch 2 taken 4224 times.
✓ Branch 3 taken 162 times.
 4386 if (it == registered_fds_.end())
427 4224 return;
428
429
1/2
✓ Branch 0 taken 162 times.
✗ Branch 1 not taken.
 162 if (events & event_read)
430 162 it->second.read_op = nullptr;
431
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 162 times.
 162 if (events & event_write)
432 ✗ it->second.write_op = nullptr;
433
434 // Remove entry if both are null
435
3/6
✓ Branch 1 taken 162 times.
✗ Branch 2 not taken.
✓ Branch 4 taken 162 times.
✗ Branch 5 not taken.
✓ Branch 6 taken 162 times.
✗ Branch 7 not taken.
 162 if (!it->second.read_op && !it->second.write_op)
436 {
437
1/1
✓ Branch 1 taken 162 times.
 162 registered_fds_.erase(it);
438
439 // Recalculate max_fd_ if needed
440
2/2
✓ Branch 0 taken 161 times.
✓ Branch 1 taken 1 time.
 162 if (fd == max_fd_)
441 {
442 161 max_fd_ = pipe_fds_[0]; // At minimum, the pipe read end
443
1/2
✗ Branch 7 not taken.
✓ Branch 8 taken 161 times.
 161 for (auto& [registered_fd, state] : registered_fds_)
444 {
445 ✗ if (registered_fd > max_fd_)
446 ✗ max_fd_ = registered_fd;
447 }
448 }
449 }
450 4386 }
451
452 void
453 4454 select_scheduler::
454 work_started() const noexcept
455 {
456 4454 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
457 4454 }
458
459 void
460 166834 select_scheduler::
461 work_finished() const noexcept
462 {
463
2/2
✓ Branch 0 taken 90 times.
✓ Branch 1 taken 166744 times.
 333668 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 166834 }
476
477 void
478 9137 select_scheduler::
479 interrupt_reactor() const
480 {
481 9137 char byte = 1;
482
1/1
✓ Branch 1 taken 9137 times.
 9137 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
483 9137 }
484
485 void
486 162374 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 162374 times.
 162374 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 2284 times.
✓ Branch 1 taken 160090 times.
✓ Branch 2 taken 2280 times.
✓ Branch 3 taken 4 times.
 162374 else if (reactor_running_ && !reactor_interrupted_)
496 {
497 // No idle workers but reactor is running - interrupt it
498 2280 reactor_interrupted_ = true;
499 2280 lock.unlock();
500 2280 interrupt_reactor();
501 }
502 else
503 {
504 // No one to wake
505 160094 lock.unlock();
506 }
507 162374 }
508
509 struct work_guard
510 {
511 select_scheduler const* self;
512 166666 ~work_guard() { self->work_finished(); }
513 };
514
515 long
516 6562 select_scheduler::
517 calculate_timeout(long requested_timeout_us) const
518 {
519
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 6562 times.
 6562 if (requested_timeout_us == 0)
520 ✗ return 0;
521
522 6562 auto nearest = timer_svc_->nearest_expiry();
523
3/3
✓ Branch 2 taken 6562 times.
✓ Branch 4 taken 35 times.
✓ Branch 5 taken 6527 times.
 6562 if (nearest == timer_service::time_point::max())
524 35 return requested_timeout_us;
525
526 6527 auto now = std::chrono::steady_clock::now();
527
3/3
✓ Branch 1 taken 6527 times.
✓ Branch 4 taken 2 times.
✓ Branch 5 taken 6525 times.
 6527 if (nearest <= now)
528 2 return 0;
529
530
1/1
✓ Branch 1 taken 6525 times.
 6525 auto timer_timeout_us = std::chrono::duration_cast<std::chrono::microseconds>(
531
1/1
✓ Branch 1 taken 6525 times.
 13050 nearest - now).count();
532
533
1/2
✓ Branch 0 taken 6525 times.
✗ Branch 1 not taken.
 6525 if (requested_timeout_us < 0)
534 6525 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 81962 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 75400 times.
✓ Branch 1 taken 6562 times.
✓ Branch 3 taken 6562 times.
 81962 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 1311392 times.
✓ Branch 1 taken 81962 times.
 1393354 FD_ZERO(&read_fds);
551
2/2
✓ Branch 0 taken 1311392 times.
✓ Branch 1 taken 81962 times.
 1393354 FD_ZERO(&write_fds);
552
2/2
✓ Branch 0 taken 1311392 times.
✓ Branch 1 taken 81962 times.
 1393354 FD_ZERO(&except_fds);
553
554 // Always include the interrupt pipe
555 81962 FD_SET(pipe_fds_[0], &read_fds);
556 81962 int nfds = pipe_fds_[0];
557
558 // Add registered fds
559
2/2
✓ Branch 7 taken 10488 times.
✓ Branch 8 taken 81962 times.
 92450 for (auto& [fd, state] : registered_fds_)
560 {
561
2/2
✓ Branch 0 taken 8402 times.
✓ Branch 1 taken 2086 times.
 10488 if (state.read_op)
562 8402 FD_SET(fd, &read_fds);
563
2/2
✓ Branch 0 taken 2086 times.
✓ Branch 1 taken 8402 times.
 10488 if (state.write_op)
564 {
565 2086 FD_SET(fd, &write_fds);
566 // Also monitor for errors on connect operations
567 2086 FD_SET(fd, &except_fds);
568 }
569
2/2
✓ Branch 0 taken 8405 times.
✓ Branch 1 taken 2083 times.
 10488 if (fd > nfds)
570 8405 nfds = fd;
571 }
572
573 // Convert timeout to timeval
574 struct timeval tv;
575 81962 struct timeval* tv_ptr = nullptr;
576
2/2
✓ Branch 0 taken 81927 times.
✓ Branch 1 taken 35 times.
 81962 if (effective_timeout_us >= 0)
577 {
578 81927 tv.tv_sec = effective_timeout_us / 1000000;
579 81927 tv.tv_usec = effective_timeout_us % 1000000;
580 81927 tv_ptr = &tv;
581 }
582
583
1/1
✓ Branch 1 taken 81962 times.
 81962 lock.unlock();
584
585
1/1
✓ Branch 1 taken 81962 times.
 81962 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
586 81962 int saved_errno = errno;
587
588 // Process timers outside the lock
589
1/1
✓ Branch 1 taken 81962 times.
 81962 timer_svc_->process_expired();
590
591
1/4
✗ Branch 0 not taken.
✓ Branch 1 taken 81962 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
 81962 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 81962 times.
 81962 lock.lock();
596
597 // Drain the interrupt pipe if readable
598
3/4
✓ Branch 0 taken 6890 times.
✓ Branch 1 taken 75072 times.
✓ Branch 2 taken 6890 times.
✗ Branch 3 not taken.
 81962 if (ready > 0 && FD_ISSET(pipe_fds_[0], &read_fds))
599 {
600 char buf[256];
601
3/3
✓ Branch 1 taken 13780 times.
✓ Branch 3 taken 6890 times.
✓ Branch 4 taken 6890 times.
 13780 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) {}
602 }
603
604 // Process I/O completions
605 81962 int completions_queued = 0;
606
2/2
✓ Branch 0 taken 6890 times.
✓ Branch 1 taken 75072 times.
 81962 if (ready > 0)
607 {
608 // Iterate over registered fds (copy keys to avoid iterator invalidation)
609 6890 std::vector<int> fds_to_check;
610
1/1
✓ Branch 2 taken 6890 times.
 6890 fds_to_check.reserve(registered_fds_.size());
611
2/2
✓ Branch 7 taken 8435 times.
✓ Branch 8 taken 6890 times.
 15325 for (auto& [fd, state] : registered_fds_)
612
1/1
✓ Branch 1 taken 8435 times.
 8435 fds_to_check.push_back(fd);
613
614
2/2
✓ Branch 5 taken 8435 times.
✓ Branch 6 taken 6890 times.
 15325 for (int fd : fds_to_check)
615 {
616
1/1
✓ Branch 1 taken 8435 times.
 8435 auto it = registered_fds_.find(fd);
617
1/2
✗ Branch 2 not taken.
✓ Branch 3 taken 8435 times.
 8435 if (it == registered_fds_.end())
618 ✗ continue;
619
620 8435 auto& state = it->second;
621
622 // Check for errors (especially for connect operations)
623 8435 bool has_error = FD_ISSET(fd, &except_fds);
624
625 // Process read readiness
626
5/6
✓ Branch 0 taken 6349 times.
✓ Branch 1 taken 2086 times.
✓ Branch 2 taken 4143 times.
✓ Branch 3 taken 2206 times.
✗ Branch 4 not taken.
✓ Branch 5 taken 4143 times.
 8435 if (state.read_op && (FD_ISSET(fd, &read_fds) || has_error))
627 {
628 2206 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 2206 auto prev = op->registered.exchange(
632 select_registration_state::unregistered, std::memory_order_acq_rel);
633
1/2
✓ Branch 0 taken 2206 times.
✗ Branch 1 not taken.
 2206 if (prev != select_registration_state::unregistered)
634 {
635 2206 state.read_op = nullptr;
636
637
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2206 times.
 2206 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 2206 op->perform_io();
650 }
651
652 2206 completed_ops_.push(op);
653 2206 ++completions_queued;
654 }
655 }
656
657 // Process write readiness
658
3/6
✓ Branch 0 taken 2086 times.
✓ Branch 1 taken 6349 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 2086 times.
✗ Branch 4 not taken.
✗ Branch 5 not taken.
 8435 if (state.write_op && (FD_ISSET(fd, &write_fds) || has_error))
659 {
660 2086 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 2086 auto prev = op->registered.exchange(
664 select_registration_state::unregistered, std::memory_order_acq_rel);
665
1/2
✓ Branch 0 taken 2086 times.
✗ Branch 1 not taken.
 2086 if (prev != select_registration_state::unregistered)
666 {
667 2086 state.write_op = nullptr;
668
669
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 2086 times.
 2086 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 2086 op->perform_io();
682 }
683
684 2086 completed_ops_.push(op);
685 2086 ++completions_queued;
686 }
687 }
688
689 // Clean up empty entries
690
3/4
✓ Branch 0 taken 4292 times.
✓ Branch 1 taken 4143 times.
✓ Branch 2 taken 4292 times.
✗ Branch 3 not taken.
 8435 if (!state.read_op && !state.write_op)
691
1/1
✓ Branch 1 taken 4292 times.
 4292 registered_fds_.erase(it);
692 }
693 6890 }
694
695
2/2
✓ Branch 0 taken 2209 times.
✓ Branch 1 taken 79753 times.
 81962 if (completions_queued > 0)
696 {
697
2/2
✓ Branch 0 taken 126 times.
✓ Branch 1 taken 2083 times.
 2209 if (completions_queued == 1)
698 126 wakeup_event_.notify_one();
699 else
700 2083 wakeup_event_.notify_all();
701 }
702 81962 }
703
704 std::size_t
705 166755 select_scheduler::
706 do_one(long timeout_us)
707 {
708
1/1
✓ Branch 1 taken 166755 times.
 166755 std::unique_lock lock(mutex_);
709
710 for (;;)
711 {
712
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 248717 times.
 248717 if (stopped_.load(std::memory_order_acquire))
713 ✗ return 0;
714
715 248717 scheduler_op* op = completed_ops_.pop();
716
717
2/2
✓ Branch 0 taken 82051 times.
✓ Branch 1 taken 166666 times.
 248717 if (op == &task_op_)
718 {
719 82051 bool more_handlers = !completed_ops_.empty();
720
721
2/2
✓ Branch 0 taken 6651 times.
✓ Branch 1 taken 75400 times.
 82051 if (!more_handlers)
722 {
723
2/2
✓ Branch 1 taken 89 times.
✓ Branch 2 taken 6562 times.
 13302 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 6562 times.
 6562 if (timeout_us == 0)
729 {
730 ✗ completed_ops_.push(&task_op_);
731 ✗ return 0;
732 }
733 }
734
735
3/4
✓ Branch 0 taken 6562 times.
✓ Branch 1 taken 75400 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 6562 times.
 81962 reactor_interrupted_ = more_handlers || timeout_us == 0;
736 81962 reactor_running_ = true;
737
738
3/4
✓ Branch 0 taken 75400 times.
✓ Branch 1 taken 6562 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 75400 times.
 81962 if (more_handlers && idle_thread_count_ > 0)
739 ✗ wakeup_event_.notify_one();
740
741
1/1
✓ Branch 1 taken 81962 times.
 81962 run_reactor(lock);
742
743 81962 reactor_running_ = false;
744 81962 completed_ops_.push(&task_op_);
745 81962 continue;
746 81962 }
747
748
1/2
✓ Branch 0 taken 166666 times.
✗ Branch 1 not taken.
 166666 if (op != nullptr)
749 {
750
1/1
✓ Branch 1 taken 166666 times.
 166666 lock.unlock();
751 166666 work_guard g{this};
752
1/1
✓ Branch 1 taken 166666 times.
 166666 (*op)();
753 166666 return 1;
754 166666 }
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 81962 }
769 166755 }
770
771 } // namespace boost::corosio::detail
772
773 #endif // BOOST_COROSIO_HAS_SELECT
774