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) 61.8% Branches (165/267)
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/timer_service.hpp"
17 #include "src/detail/make_err.hpp"
18 #include "src/detail/posix/resolver_service.hpp"
19 #include "src/detail/posix/signals.hpp"
20
21 #include <boost/corosio/detail/except.hpp>
22 #include <boost/corosio/detail/thread_local_ptr.hpp>
23
24 #include <chrono>
25 #include <limits>
26
27 #include <errno.h>
28 #include <fcntl.h>
29 #include <sys/select.h>
30 #include <sys/socket.h>
31 #include <unistd.h>
32
33 /*
34 select Scheduler - Single Reactor Model
35 =======================================
36
37 This scheduler mirrors the epoll_scheduler design but uses select() instead
38 of epoll for I/O multiplexing. The thread coordination strategy is identical:
39 one thread becomes the "reactor" while others wait on a condition variable.
40
41 Thread Model
42 ------------
43 - ONE thread runs select() at a time (the reactor thread)
44 - OTHER threads wait on wakeup_event_ (condition variable) for handlers
45 - When work is posted, exactly one waiting thread wakes via notify_one()
46
47 Key Differences from epoll
48 --------------------------
49 - Uses self-pipe instead of eventfd for interruption (more portable)
50 - fd_set rebuilding each iteration (O(n) vs O(1) for epoll)
51 - FD_SETSIZE limit (~1024 fds on most systems)
52 - Level-triggered only (no edge-triggered mode)
53
54 Self-Pipe Pattern
55 -----------------
56 To interrupt a blocking select() call (e.g., when work is posted or a timer
57 expires), we write a byte to pipe_fds_[1]. The read end pipe_fds_[0] is
58 always in the read_fds set, so select() returns immediately. We drain the
59 pipe to clear the readable state.
60
61 fd-to-op Mapping
62 ----------------
63 We use an unordered_map<int, fd_state> to track which operations are
64 registered for each fd. This allows O(1) lookup when select() returns
65 ready fds. Each fd can have at most one read op and one write op registered.
66 */
67
68 namespace boost::corosio::detail {
69
70 namespace {
71
72 struct scheduler_context
73 {
74 select_scheduler const* key;
75 scheduler_context* next;
76 };
77
78 corosio::detail::thread_local_ptr<scheduler_context> context_stack;
79
80 struct thread_context_guard
81 {
82 scheduler_context frame_;
83
84 120 explicit thread_context_guard(
85 select_scheduler const* ctx) noexcept
86 120 : frame_{ctx, context_stack.get()}
87 {
88 120 context_stack.set(&frame_);
89 120 }
90
91 120 ~thread_context_guard() noexcept
92 {
93 120 context_stack.set(frame_.next);
94 120 }
95 };
96
97 } // namespace
98
99 133 select_scheduler::
100 select_scheduler(
101 capy::execution_context& ctx,
102 133 int)
103 133 : pipe_fds_{-1, -1}
104 133 , outstanding_work_(0)
105 133 , stopped_(false)
106 133 , shutdown_(false)
107 133 , max_fd_(-1)
108 133 , reactor_running_(false)
109 133 , reactor_interrupted_(false)
110 266 , idle_thread_count_(0)
111 {
112 // Create self-pipe for interrupting select()
113
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 133 times.
 133 if (::pipe(pipe_fds_) < 0)
114 ✗ detail::throw_system_error(make_err(errno), "pipe");
115
116 // Set both ends to non-blocking and close-on-exec
117
2/2
✓ Branch 0 taken 266 times.
✓ Branch 1 taken 133 times.
 399 for (int i = 0; i < 2; ++i)
118 {
119
1/1
✓ Branch 1 taken 266 times.
 266 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
120
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 266 times.
 266 if (flags == -1)
121 {
122 ✗ int errn = errno;
123 ✗ ::close(pipe_fds_[0]);
124 ✗ ::close(pipe_fds_[1]);
125 ✗ detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
126 }
127
2/3
✓ Branch 1 taken 266 times.
✗ Branch 3 not taken.
✓ Branch 4 taken 266 times.
 266 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
128 {
129 ✗ int errn = errno;
130 ✗ ::close(pipe_fds_[0]);
131 ✗ ::close(pipe_fds_[1]);
132 ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
133 }
134
2/3
✓ Branch 1 taken 266 times.
✗ Branch 3 not taken.
✓ Branch 4 taken 266 times.
 266 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
135 {
136 ✗ int errn = errno;
137 ✗ ::close(pipe_fds_[0]);
138 ✗ ::close(pipe_fds_[1]);
139 ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
140 }
141 }
142
143
1/1
✓ Branch 1 taken 133 times.
 133 timer_svc_ = &get_timer_service(ctx, *this);
144
1/1
✓ Branch 3 taken 133 times.
 133 timer_svc_->set_on_earliest_changed(
145 timer_service::callback(
146 this,
147 3445 [](void* p) { static_cast<select_scheduler*>(p)->interrupt_reactor(); }));
148
149 // Initialize resolver service
150
1/1
✓ Branch 1 taken 133 times.
 133 get_resolver_service(ctx, *this);
151
152 // Initialize signal service
153
1/1
✓ Branch 1 taken 133 times.
 133 get_signal_service(ctx, *this);
154
155 // Push task sentinel to interleave reactor runs with handler execution
156 133 completed_ops_.push(&task_op_);
157 133 }
158
159 266 select_scheduler::
160 133 ~select_scheduler()
161 {
162
1/2
✓ Branch 0 taken 133 times.
✗ Branch 1 not taken.
 133 if (pipe_fds_[0] >= 0)
163 133 ::close(pipe_fds_[0]);
164
1/2
✓ Branch 0 taken 133 times.
✗ Branch 1 not taken.
 133 if (pipe_fds_[1] >= 0)
165 133 ::close(pipe_fds_[1]);
166 266 }
167
168 void
169 133 select_scheduler::
170 shutdown()
171 {
172 {
173
1/1
✓ Branch 1 taken 133 times.
 133 std::unique_lock lock(mutex_);
174 133 shutdown_ = true;
175
176
2/2
✓ Branch 1 taken 133 times.
✓ Branch 2 taken 133 times.
 266 while (auto* h = completed_ops_.pop())
177 {
178
1/2
✓ Branch 0 taken 133 times.
✗ Branch 1 not taken.
 133 if (h == &task_op_)
179 133 continue;
180 ✗ lock.unlock();
181 ✗ h->destroy();
182 ✗ lock.lock();
183 133 }
184 133 }
185
186 133 outstanding_work_.store(0, std::memory_order_release);
187
188
1/2
✓ Branch 0 taken 133 times.
✗ Branch 1 not taken.
 133 if (pipe_fds_[1] >= 0)
189 133 interrupt_reactor();
190
191 133 wakeup_event_.notify_all();
192 133 }
193
194 void
195 3782 select_scheduler::
196 post(std::coroutine_handle<> h) const
197 {
198 struct post_handler final
199 : scheduler_op
200 {
201 std::coroutine_handle<> h_;
202
203 explicit
204 3782 post_handler(std::coroutine_handle<> h)
205 3782 : h_(h)
206 {
207 3782 }
208
209 7564 ~post_handler() = default;
210
211 3782 void operator()() override
212 {
213 3782 auto h = h_;
214
1/2
✓ Branch 0 taken 3782 times.
✗ Branch 1 not taken.
 3782 delete this;
215
1/1
✓ Branch 1 taken 3782 times.
 3782 h.resume();
216 3782 }
217
218 ✗ void destroy() override
219 {
220 ✗ delete this;
221 ✗ }
222 };
223
224
1/1
✓ Branch 1 taken 3782 times.
 3782 auto ph = std::make_unique<post_handler>(h);
225 3782 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
226
227
1/1
✓ Branch 1 taken 3782 times.
 3782 std::unique_lock lock(mutex_);
228 3782 completed_ops_.push(ph.release());
229
1/1
✓ Branch 1 taken 3782 times.
 3782 wake_one_thread_and_unlock(lock);
230 3782 }
231
232 void
233 164726 select_scheduler::
234 post(scheduler_op* h) const
235 {
236 164726 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
237
238
1/1
✓ Branch 1 taken 164726 times.
 164726 std::unique_lock lock(mutex_);
239 164726 completed_ops_.push(h);
240
1/1
✓ Branch 1 taken 164726 times.
 164726 wake_one_thread_and_unlock(lock);
241 164726 }
242
243 void
244 4019 select_scheduler::
245 on_work_started() noexcept
246 {
247 4019 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
248 4019 }
249
250 void
251 4013 select_scheduler::
252 on_work_finished() noexcept
253 {
254
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 4013 times.
 8026 if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
255 ✗ stop();
256 4013 }
257
258 bool
259 552 select_scheduler::
260 running_in_this_thread() const noexcept
261 {
262
2/2
✓ Branch 1 taken 368 times.
✓ Branch 2 taken 184 times.
 552 for (auto* c = context_stack.get(); c != nullptr; c = c->next)
263
1/2
✓ Branch 0 taken 368 times.
✗ Branch 1 not taken.
 368 if (c->key == this)
264 368 return true;
265 184 return false;
266 }
267
268 void
269 3 select_scheduler::
270 stop()
271 {
272 3 bool expected = false;
273
1/2
✓ Branch 1 taken 3 times.
✗ Branch 2 not taken.
 3 if (stopped_.compare_exchange_strong(expected, true,
274 std::memory_order_release, std::memory_order_relaxed))
275 {
276 // Wake all threads so they notice stopped_ and exit
277 {
278
1/1
✓ Branch 1 taken 3 times.
 3 std::lock_guard lock(mutex_);
279 3 wakeup_event_.notify_all();
280 3 }
281
1/1
✓ Branch 1 taken 3 times.
 3 interrupt_reactor();
282 }
283 3 }
284
285 bool
286 3 select_scheduler::
287 stopped() const noexcept
288 {
289 3 return stopped_.load(std::memory_order_acquire);
290 }
291
292 void
293 34 select_scheduler::
294 restart()
295 {
296 34 stopped_.store(false, std::memory_order_release);
297 34 }
298
299 std::size_t
300 96 select_scheduler::
301 run()
302 {
303
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 96 times.
 96 if (stopped_.load(std::memory_order_acquire))
304 ✗ return 0;
305
306
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 96 times.
 192 if (outstanding_work_.load(std::memory_order_acquire) == 0)
307 {
308 ✗ stop();
309 ✗ return 0;
310 }
311
312 96 thread_context_guard ctx(this);
313
314 96 std::size_t n = 0;
315
3/3
✓ Branch 1 taken 175158 times.
✓ Branch 3 taken 175062 times.
✓ Branch 4 taken 96 times.
 175158 while (do_one(-1))
316
1/2
✓ Branch 1 taken 175062 times.
✗ Branch 2 not taken.
 175062 if (n != (std::numeric_limits<std::size_t>::max)())
317 175062 ++n;
318 96 return n;
319 96 }
320
321 std::size_t
322 ✗ select_scheduler::
323 run_one()
324 {
325 ✗ if (stopped_.load(std::memory_order_acquire))
326 ✗ return 0;
327
328 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
329 {
330 ✗ stop();
331 ✗ return 0;
332 }
333
334 ✗ thread_context_guard ctx(this);
335 ✗ return do_one(-1);
336 ✗ }
337
338 std::size_t
339 27 select_scheduler::
340 wait_one(long usec)
341 {
342
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 27 times.
 27 if (stopped_.load(std::memory_order_acquire))
343 ✗ return 0;
344
345
2/2
✓ Branch 1 taken 3 times.
✓ Branch 2 taken 24 times.
 54 if (outstanding_work_.load(std::memory_order_acquire) == 0)
346 {
347
1/1
✓ Branch 1 taken 3 times.
 3 stop();
348 3 return 0;
349 }
350
351 24 thread_context_guard ctx(this);
352
1/1
✓ Branch 1 taken 24 times.
 24 return do_one(usec);
353 24 }
354
355 std::size_t
356 ✗ select_scheduler::
357 poll()
358 {
359 ✗ if (stopped_.load(std::memory_order_acquire))
360 ✗ return 0;
361
362 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
363 {
364 ✗ stop();
365 ✗ return 0;
366 }
367
368 ✗ thread_context_guard ctx(this);
369
370 ✗ std::size_t n = 0;
371 ✗ while (do_one(0))
372 ✗ if (n != (std::numeric_limits<std::size_t>::max)())
373 ✗ ++n;
374 ✗ return n;
375 ✗ }
376
377 std::size_t
378 ✗ select_scheduler::
379 poll_one()
380 {
381 ✗ if (stopped_.load(std::memory_order_acquire))
382 ✗ return 0;
383
384 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
385 {
386 ✗ stop();
387 ✗ return 0;
388 }
389
390 ✗ thread_context_guard ctx(this);
391 ✗ return do_one(0);
392 ✗ }
393
394 void
395 6739 select_scheduler::
396 register_fd(int fd, select_op* op, int events) const
397 {
398 // Validate fd is within select() limits
399
2/4
✓ Branch 0 taken 6739 times.
✗ Branch 1 not taken.
✗ Branch 2 not taken.
✓ Branch 3 taken 6739 times.
 6739 if (fd < 0 || fd >= FD_SETSIZE)
400 ✗ detail::throw_system_error(make_err(EINVAL), "select: fd out of range");
401
402 {
403
1/1
✓ Branch 1 taken 6739 times.
 6739 std::lock_guard lock(mutex_);
404
405
1/1
✓ Branch 1 taken 6739 times.
 6739 auto& state = registered_fds_[fd];
406
2/2
✓ Branch 0 taken 3510 times.
✓ Branch 1 taken 3229 times.
 6739 if (events & event_read)
407 3510 state.read_op = op;
408
2/2
✓ Branch 0 taken 3229 times.
✓ Branch 1 taken 3510 times.
 6739 if (events & event_write)
409 3229 state.write_op = op;
410
411
2/2
✓ Branch 0 taken 227 times.
✓ Branch 1 taken 6512 times.
 6739 if (fd > max_fd_)
412 227 max_fd_ = fd;
413 6739 }
414
415 // Wake the reactor so a thread blocked in select() rebuilds its fd_sets
416 // with the newly registered fd.
417 6739 interrupt_reactor();
418 6739 }
419
420 void
421 6670 select_scheduler::
422 deregister_fd(int fd, int events) const
423 {
424
1/1
✓ Branch 1 taken 6670 times.
 6670 std::lock_guard lock(mutex_);
425
426
1/1
✓ Branch 1 taken 6670 times.
 6670 auto it = registered_fds_.find(fd);
427
2/2
✓ Branch 2 taken 6509 times.
✓ Branch 3 taken 161 times.
 6670 if (it == registered_fds_.end())
428 6509 return;
429
430
1/2
✓ Branch 0 taken 161 times.
✗ Branch 1 not taken.
 161 if (events & event_read)
431 161 it->second.read_op = nullptr;
432
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 161 times.
 161 if (events & event_write)
433 ✗ it->second.write_op = nullptr;
434
435 // Remove entry if both are null
436
3/6
✓ Branch 1 taken 161 times.
✗ Branch 2 not taken.
✓ Branch 4 taken 161 times.
✗ Branch 5 not taken.
✓ Branch 6 taken 161 times.
✗ Branch 7 not taken.
 161 if (!it->second.read_op && !it->second.write_op)
437 {
438
1/1
✓ Branch 1 taken 161 times.
 161 registered_fds_.erase(it);
439
440 // Recalculate max_fd_ if needed
441
1/2
✓ Branch 0 taken 161 times.
✗ Branch 1 not taken.
 161 if (fd == max_fd_)
442 {
443 161 max_fd_ = pipe_fds_[0]; // At minimum, the pipe read end
444
1/2
✗ Branch 7 not taken.
✓ Branch 8 taken 161 times.
 161 for (auto& [registered_fd, state] : registered_fds_)
445 {
446 ✗ if (registered_fd > max_fd_)
447 ✗ max_fd_ = registered_fd;
448 }
449 }
450 }
451 6670 }
452
453 void
454 6739 select_scheduler::
455 work_started() const noexcept
456 {
457 6739 outstanding_work_.fetch_add(1, std::memory_order_relaxed);
458 6739 }
459
460 void
461 175253 select_scheduler::
462 work_finished() const noexcept
463 {
464
2/2
✓ Branch 0 taken 99 times.
✓ Branch 1 taken 175154 times.
 350506 if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
465 {
466 // Last work item completed - wake all threads so they can exit.
467 99 std::unique_lock lock(mutex_);
468 99 wakeup_event_.notify_all();
469
1/4
✗ Branch 0 not taken.
✓ Branch 1 taken 99 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
 99 if (reactor_running_ && !reactor_interrupted_)
470 {
471 ✗ reactor_interrupted_ = true;
472 ✗ lock.unlock();
473 ✗ interrupt_reactor();
474 }
475 99 }
476 175253 }
477
478 void
479 13755 select_scheduler::
480 interrupt_reactor() const
481 {
482 13755 char byte = 1;
483
1/1
✓ Branch 1 taken 13755 times.
 13755 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
484 13755 }
485
486 void
487 168508 select_scheduler::
488 wake_one_thread_and_unlock(std::unique_lock<std::mutex>& lock) const
489 {
490
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 168508 times.
 168508 if (idle_thread_count_ > 0)
491 {
492 // Idle worker exists - wake it via condvar
493 ✗ wakeup_event_.notify_one();
494 ✗ lock.unlock();
495 }
496
4/4
✓ Branch 0 taken 3441 times.
✓ Branch 1 taken 165067 times.
✓ Branch 2 taken 3435 times.
✓ Branch 3 taken 6 times.
 168508 else if (reactor_running_ && !reactor_interrupted_)
497 {
498 // No idle workers but reactor is running - interrupt it
499 3435 reactor_interrupted_ = true;
500 3435 lock.unlock();
501 3435 interrupt_reactor();
502 }
503 else
504 {
505 // No one to wake
506 165073 lock.unlock();
507 }
508 168508 }
509
510 struct work_guard
511 {
512 select_scheduler const* self;
513 175086 ~work_guard() { self->work_finished(); }
514 };
515
516 long
517 10002 select_scheduler::
518 calculate_timeout(long requested_timeout_us) const
519 {
520
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 10002 times.
 10002 if (requested_timeout_us == 0)
521 ✗ return 0;
522
523 10002 auto nearest = timer_svc_->nearest_expiry();
524
3/3
✓ Branch 2 taken 10002 times.
✓ Branch 4 taken 35 times.
✓ Branch 5 taken 9967 times.
 10002 if (nearest == timer_service::time_point::max())
525 35 return requested_timeout_us;
526
527 9967 auto now = std::chrono::steady_clock::now();
528
3/3
✓ Branch 1 taken 9967 times.
✓ Branch 4 taken 20 times.
✓ Branch 5 taken 9947 times.
 9967 if (nearest <= now)
529 20 return 0;
530
531
1/1
✓ Branch 1 taken 9947 times.
 9947 auto timer_timeout_us = std::chrono::duration_cast<std::chrono::microseconds>(
532
1/1
✓ Branch 1 taken 9947 times.
 19894 nearest - now).count();
533
534
1/2
✓ Branch 0 taken 9947 times.
✗ Branch 1 not taken.
 9947 if (requested_timeout_us < 0)
535 9947 return static_cast<long>(timer_timeout_us);
536
537 ✗ return static_cast<long>((std::min)(
538 ✗ static_cast<long long>(requested_timeout_us),
539 ✗ static_cast<long long>(timer_timeout_us)));
540 }
541
542 void
543 95825 select_scheduler::
544 run_reactor(std::unique_lock<std::mutex>& lock)
545 {
546 // Calculate timeout considering timers, use 0 if interrupted
547
3/3
✓ Branch 0 taken 85823 times.
✓ Branch 1 taken 10002 times.
✓ Branch 3 taken 10002 times.
 95825 long effective_timeout_us = reactor_interrupted_ ? 0 : calculate_timeout(-1);
548
549 // Build fd_sets from registered_fds_
550 fd_set read_fds, write_fds, except_fds;
551
2/2
✓ Branch 0 taken 1533200 times.
✓ Branch 1 taken 95825 times.
 1629025 FD_ZERO(&read_fds);
552
2/2
✓ Branch 0 taken 1533200 times.
✓ Branch 1 taken 95825 times.
 1629025 FD_ZERO(&write_fds);
553
2/2
✓ Branch 0 taken 1533200 times.
✓ Branch 1 taken 95825 times.
 1629025 FD_ZERO(&except_fds);
554
555 // Always include the interrupt pipe
556 95825 FD_SET(pipe_fds_[0], &read_fds);
557 95825 int nfds = pipe_fds_[0];
558
559 // Add registered fds
560
2/2
✓ Branch 7 taken 16191 times.
✓ Branch 8 taken 95825 times.
 112016 for (auto& [fd, state] : registered_fds_)
561 {
562
2/2
✓ Branch 0 taken 12962 times.
✓ Branch 1 taken 3229 times.
 16191 if (state.read_op)
563 12962 FD_SET(fd, &read_fds);
564
2/2
✓ Branch 0 taken 3229 times.
✓ Branch 1 taken 12962 times.
 16191 if (state.write_op)
565 {
566 3229 FD_SET(fd, &write_fds);
567 // Also monitor for errors on connect operations
568 3229 FD_SET(fd, &except_fds);
569 }
570
2/2
✓ Branch 0 taken 12965 times.
✓ Branch 1 taken 3226 times.
 16191 if (fd > nfds)
571 12965 nfds = fd;
572 }
573
574 // Convert timeout to timeval
575 struct timeval tv;
576 95825 struct timeval* tv_ptr = nullptr;
577
2/2
✓ Branch 0 taken 95790 times.
✓ Branch 1 taken 35 times.
 95825 if (effective_timeout_us >= 0)
578 {
579 95790 tv.tv_sec = effective_timeout_us / 1000000;
580 95790 tv.tv_usec = effective_timeout_us % 1000000;
581 95790 tv_ptr = &tv;
582 }
583
584
1/1
✓ Branch 1 taken 95825 times.
 95825 lock.unlock();
585
586
1/1
✓ Branch 1 taken 95825 times.
 95825 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
587 95825 int saved_errno = errno;
588
589 // Process timers outside the lock
590
1/1
✓ Branch 1 taken 95825 times.
 95825 timer_svc_->process_expired();
591
592
1/4
✗ Branch 0 not taken.
✓ Branch 1 taken 95825 times.
✗ Branch 2 not taken.
✗ Branch 3 not taken.
 95825 if (ready < 0 && saved_errno != EINTR)
593 ✗ detail::throw_system_error(make_err(saved_errno), "select");
594
595 // Re-acquire lock before modifying completed_ops_
596
1/1
✓ Branch 1 taken 95825 times.
 95825 lock.lock();
597
598 // Drain the interrupt pipe if readable
599
3/4
✓ Branch 0 taken 10333 times.
✓ Branch 1 taken 85492 times.
✓ Branch 2 taken 10333 times.
✗ Branch 3 not taken.
 95825 if (ready > 0 && FD_ISSET(pipe_fds_[0], &read_fds))
600 {
601 char buf[256];
602
3/3
✓ Branch 1 taken 20666 times.
✓ Branch 3 taken 10333 times.
✓ Branch 4 taken 10333 times.
 20666 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) {}
603 }
604
605 // Process I/O completions
606 95825 int completions_queued = 0;
607
2/2
✓ Branch 0 taken 10333 times.
✓ Branch 1 taken 85492 times.
 95825 if (ready > 0)
608 {
609 // Iterate over registered fds (copy keys to avoid iterator invalidation)
610 10333 std::vector<int> fds_to_check;
611
1/1
✓ Branch 2 taken 10333 times.
 10333 fds_to_check.reserve(registered_fds_.size());
612
2/2
✓ Branch 7 taken 12996 times.
✓ Branch 8 taken 10333 times.
 23329 for (auto& [fd, state] : registered_fds_)
613
1/1
✓ Branch 1 taken 12996 times.
 12996 fds_to_check.push_back(fd);
614
615
2/2
✓ Branch 5 taken 12996 times.
✓ Branch 6 taken 10333 times.
 23329 for (int fd : fds_to_check)
616 {
617
1/1
✓ Branch 1 taken 12996 times.
 12996 auto it = registered_fds_.find(fd);
618
1/2
✗ Branch 2 not taken.
✓ Branch 3 taken 12996 times.
 12996 if (it == registered_fds_.end())
619 ✗ continue;
620
621 12996 auto& state = it->second;
622
623 // Check for errors (especially for connect operations)
624 12996 bool has_error = FD_ISSET(fd, &except_fds);
625
626 // Process read readiness
627
5/6
✓ Branch 0 taken 9767 times.
✓ Branch 1 taken 3229 times.
✓ Branch 2 taken 6418 times.
✓ Branch 3 taken 3349 times.
✗ Branch 4 not taken.
✓ Branch 5 taken 6418 times.
 12996 if (state.read_op && (FD_ISSET(fd, &read_fds) || has_error))
628 {
629 3349 auto* op = state.read_op;
630 // Claim the op by exchanging to unregistered. Both registering and
631 // registered states mean the op is ours to complete.
632 3349 auto prev = op->registered.exchange(
633 select_registration_state::unregistered, std::memory_order_acq_rel);
634
1/2
✓ Branch 0 taken 3349 times.
✗ Branch 1 not taken.
 3349 if (prev != select_registration_state::unregistered)
635 {
636 3349 state.read_op = nullptr;
637
638
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 3349 times.
 3349 if (has_error)
639 {
640 ✗ int errn = 0;
641 ✗ socklen_t len = sizeof(errn);
642 ✗ if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, &errn, &len) < 0)
643 ✗ errn = errno;
644 ✗ if (errn == 0)
645 ✗ errn = EIO;
646 ✗ op->complete(errn, 0);
647 }
648 else
649 {
650 3349 op->perform_io();
651 }
652
653 3349 completed_ops_.push(op);
654 3349 ++completions_queued;
655 }
656 }
657
658 // Process write readiness
659
3/6
✓ Branch 0 taken 3229 times.
✓ Branch 1 taken 9767 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 3229 times.
✗ Branch 4 not taken.
✗ Branch 5 not taken.
 12996 if (state.write_op && (FD_ISSET(fd, &write_fds) || has_error))
660 {
661 3229 auto* op = state.write_op;
662 // Claim the op by exchanging to unregistered. Both registering and
663 // registered states mean the op is ours to complete.
664 3229 auto prev = op->registered.exchange(
665 select_registration_state::unregistered, std::memory_order_acq_rel);
666
1/2
✓ Branch 0 taken 3229 times.
✗ Branch 1 not taken.
 3229 if (prev != select_registration_state::unregistered)
667 {
668 3229 state.write_op = nullptr;
669
670
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 3229 times.
 3229 if (has_error)
671 {
672 ✗ int errn = 0;
673 ✗ socklen_t len = sizeof(errn);
674 ✗ if (::getsockopt(fd, SOL_SOCKET, SO_ERROR, &errn, &len) < 0)
675 ✗ errn = errno;
676 ✗ if (errn == 0)
677 ✗ errn = EIO;
678 ✗ op->complete(errn, 0);
679 }
680 else
681 {
682 3229 op->perform_io();
683 }
684
685 3229 completed_ops_.push(op);
686 3229 ++completions_queued;
687 }
688 }
689
690 // Clean up empty entries
691
3/4
✓ Branch 0 taken 6578 times.
✓ Branch 1 taken 6418 times.
✓ Branch 2 taken 6578 times.
✗ Branch 3 not taken.
 12996 if (!state.read_op && !state.write_op)
692
1/1
✓ Branch 1 taken 6578 times.
 6578 registered_fds_.erase(it);
693 }
694 10333 }
695
696
2/2
✓ Branch 0 taken 3352 times.
✓ Branch 1 taken 92473 times.
 95825 if (completions_queued > 0)
697 {
698
2/2
✓ Branch 0 taken 126 times.
✓ Branch 1 taken 3226 times.
 3352 if (completions_queued == 1)
699 126 wakeup_event_.notify_one();
700 else
701 3226 wakeup_event_.notify_all();
702 }
703 95825 }
704
705 std::size_t
706 175182 select_scheduler::
707 do_one(long timeout_us)
708 {
709
1/1
✓ Branch 1 taken 175182 times.
 175182 std::unique_lock lock(mutex_);
710
711 for (;;)
712 {
713
1/2
✗ Branch 1 not taken.
✓ Branch 2 taken 271007 times.
 271007 if (stopped_.load(std::memory_order_acquire))
714 ✗ return 0;
715
716 271007 scheduler_op* op = completed_ops_.pop();
717
718
2/2
✓ Branch 0 taken 95921 times.
✓ Branch 1 taken 175086 times.
 271007 if (op == &task_op_)
719 {
720 95921 bool more_handlers = !completed_ops_.empty();
721
722
2/2
✓ Branch 0 taken 10098 times.
✓ Branch 1 taken 85823 times.
 95921 if (!more_handlers)
723 {
724
2/2
✓ Branch 1 taken 96 times.
✓ Branch 2 taken 10002 times.
 20196 if (outstanding_work_.load(std::memory_order_acquire) == 0)
725 {
726 96 completed_ops_.push(&task_op_);
727 96 return 0;
728 }
729
1/2
✗ Branch 0 not taken.
✓ Branch 1 taken 10002 times.
 10002 if (timeout_us == 0)
730 {
731 ✗ completed_ops_.push(&task_op_);
732 ✗ return 0;
733 }
734 }
735
736
3/4
✓ Branch 0 taken 10002 times.
✓ Branch 1 taken 85823 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 10002 times.
 95825 reactor_interrupted_ = more_handlers || timeout_us == 0;
737 95825 reactor_running_ = true;
738
739
3/4
✓ Branch 0 taken 85823 times.
✓ Branch 1 taken 10002 times.
✗ Branch 2 not taken.
✓ Branch 3 taken 85823 times.
 95825 if (more_handlers && idle_thread_count_ > 0)
740 ✗ wakeup_event_.notify_one();
741
742
1/1
✓ Branch 1 taken 95825 times.
 95825 run_reactor(lock);
743
744 95825 reactor_running_ = false;
745 95825 completed_ops_.push(&task_op_);
746 95825 continue;
747 95825 }
748
749
1/2
✓ Branch 0 taken 175086 times.
✗ Branch 1 not taken.
 175086 if (op != nullptr)
750 {
751
1/1
✓ Branch 1 taken 175086 times.
 175086 lock.unlock();
752 175086 work_guard g{this};
753
1/1
✓ Branch 1 taken 175086 times.
 175086 (*op)();
754 175086 return 1;
755 175086 }
756
757 ✗ if (outstanding_work_.load(std::memory_order_acquire) == 0)
758 ✗ return 0;
759
760 ✗ if (timeout_us == 0)
761 ✗ return 0;
762
763 ✗ ++idle_thread_count_;
764 ✗ if (timeout_us < 0)
765 ✗ wakeup_event_.wait(lock);
766 else
767 ✗ wakeup_event_.wait_for(lock, std::chrono::microseconds(timeout_us));
768 ✗ --idle_thread_count_;
769 95825 }
770 175182 }
771
772 } // namespace boost::corosio::detail
773
774 #endif // BOOST_COROSIO_HAS_SELECT
775