TLA Line data 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 : #ifndef BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SCHEDULER_HPP
11 : #define BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SCHEDULER_HPP
12 :
13 : #include <boost/corosio/detail/config.hpp>
14 : #include <boost/corosio/detail/object_ref.hpp>
15 : #include <boost/capy/ex/execution_context.hpp>
16 : #include <boost/capy/ex/abandon.hpp>
17 :
18 : #include <boost/corosio/detail/ready_queue.hpp>
19 : #include <boost/corosio/detail/scheduler.hpp>
20 : #include <boost/corosio/detail/scheduler_op.hpp>
21 : #include <boost/corosio/detail/thread_local_ptr.hpp>
22 : #include <boost/corosio/detail/timer_service.hpp>
23 :
24 : #include <atomic>
25 : #include <chrono>
26 : #include <coroutine>
27 : #include <cstddef>
28 : #include <cstdint>
29 : #include <limits>
30 : #include <memory>
31 :
32 : #include <boost/corosio/detail/conditionally_enabled_mutex.hpp>
33 : #include <boost/corosio/detail/conditionally_enabled_event.hpp>
34 :
35 : namespace boost::corosio::detail {
36 :
37 : // Forward declarations
38 : class reactor_scheduler;
39 :
40 : /** A deregistered descriptor whose owner must outlive the reactor pass
41 : that may still hold it.
42 :
43 : An event the reactor has already read from the kernel can name a
44 : descriptor that another thread closes before the reactor queues it.
45 : The closing thread hands over a reference instead of dropping it, so
46 : the owner is neither freed nor recycled until that pass ends.
47 : */
48 : struct reactor_retirable
49 : {
50 : // All four fields are guarded by the scheduler's mutex.
51 :
52 : /// Next in the scheduler's retired list.
53 : reactor_retirable* retired_next_ = nullptr;
54 :
55 : /// Owner reference held until the pass ends.
56 : object_ref retired_ref_;
57 :
58 : /// Next in a settling thread's list of references to drop.
59 : reactor_retirable* dropped_next_ = nullptr;
60 :
61 : /// Owner reference waiting to be dropped outside the mutex.
62 : object_ref dropped_ref_;
63 :
64 : /// Move @p keep into a queued completion, if one is pending.
65 : virtual void hand_off(object_ref& keep) noexcept = 0;
66 :
67 : protected:
68 HIT 12288 : ~reactor_retirable() = default;
69 : };
70 :
71 : /** Per-thread state for a reactor scheduler.
72 :
73 : Each thread running a scheduler's event loop has one of these
74 : on a thread-local stack. It holds a private work queue and
75 : inline completion budget for speculative I/O fast paths.
76 : */
77 : struct BOOST_COROSIO_SYMBOL_VISIBLE reactor_scheduler_context
78 : {
79 : /// Scheduler this context belongs to.
80 : reactor_scheduler const* key;
81 :
82 : /// Next context frame on this thread's stack.
83 : reactor_scheduler_context* next;
84 :
85 : /// Private work queue for reduced contention.
86 : ready_queue private_queue;
87 :
88 : /// Unflushed work count for the private queue.
89 : std::int64_t private_outstanding_work;
90 :
91 : /// Remaining inline completions allowed this cycle.
92 : int inline_budget;
93 :
94 : /// Maximum inline budget (adaptive, 2-16).
95 : int inline_budget_max;
96 :
97 : /// True if no other thread absorbed queued work last cycle.
98 : bool unassisted;
99 :
100 : /// Construct a context frame linked to @a n.
101 : reactor_scheduler_context(
102 : reactor_scheduler const* k, reactor_scheduler_context* n);
103 : };
104 :
105 : /// Thread-local context stack for reactor schedulers.
106 : inline thread_local_ptr<reactor_scheduler_context> reactor_context_stack;
107 :
108 : /// Find the context frame for a scheduler on this thread.
109 : inline reactor_scheduler_context*
110 831818 : reactor_find_context(reactor_scheduler const* self) noexcept
111 : {
112 832406 : for (auto* c = reactor_context_stack.get(); c != nullptr; c = c->next)
113 : {
114 769748 : if (c->key == self)
115 769160 : return c;
116 : }
117 62658 : return nullptr;
118 : }
119 :
120 : /** Non-template base for reactor-backed scheduler implementations.
121 :
122 : Provides the complete threading model shared by epoll, kqueue,
123 : and select schedulers: signal state machine, inline completion
124 : budget, work counting, run/poll methods, and the do_one event
125 : loop.
126 :
127 : Derived classes provide platform-specific hooks by overriding:
128 : - `run_task(lock, ctx)` to run the reactor poll
129 : - `interrupt_reactor()` to wake a blocked reactor
130 :
131 : De-templated from the original CRTP design to eliminate
132 : duplicate instantiations when multiple backends are compiled
133 : into the same binary. Virtual dispatch for run_task (called
134 : once per reactor cycle, before a blocking syscall) has
135 : negligible overhead.
136 :
137 : @par Thread Safety
138 : All public member functions are thread-safe.
139 : */
140 : class reactor_scheduler : public scheduler
141 : {
142 : public:
143 : using context_type = reactor_scheduler_context;
144 : using mutex_type = conditionally_enabled_mutex;
145 : using lock_type = mutex_type::scoped_lock;
146 : using event_type = conditionally_enabled_event;
147 :
148 : /// Post a coroutine for deferred execution.
149 : void post(std::coroutine_handle<> h) const override;
150 :
151 : /// Post a scheduler operation for deferred execution.
152 : void post(scheduler_op* h) const override;
153 :
154 : /** Release an owner reference once no reactor pass can hold `d`.
155 :
156 : Called after a descriptor is deregistered. If a reactor pass is
157 : running, `keep` is parked on `d` until that pass ends. Then, or
158 : at once if no pass is running, it moves to `d`'s queued
159 : invocation if `d` is queued, and is dropped otherwise.
160 :
161 : @param d The deregistered descriptor.
162 : @param keep A reference to the descriptor's owner.
163 : */
164 : void retire_descriptor(reactor_retirable& d, object_ref keep) const;
165 :
166 : /// Post a continuation for deferred execution.
167 : void post(capy::continuation&) const override;
168 :
169 : /// Return true if called from a thread running this scheduler.
170 : bool running_in_this_thread() const noexcept override;
171 :
172 : /// Request the scheduler to stop dispatching handlers.
173 : void stop() override;
174 :
175 : /// Return true if the scheduler has been stopped.
176 : bool stopped() const noexcept override;
177 :
178 : /// Reset the stopped state so `run()` can resume.
179 : void restart() override;
180 :
181 : /// Run the event loop until no work remains.
182 : std::size_t run() override;
183 :
184 : /// Run until one handler completes or no work remains.
185 : std::size_t run_one() override;
186 :
187 : /// Run until one handler completes or @a usec elapses.
188 : std::size_t wait_one(long usec) override;
189 :
190 : /// Run ready handlers without blocking.
191 : std::size_t poll() override;
192 :
193 : /// Run at most one ready handler without blocking.
194 : std::size_t poll_one() override;
195 :
196 : /// Increment the outstanding work count.
197 : void work_started() noexcept override;
198 :
199 : /// Decrement the outstanding work count, stopping on zero.
200 : void work_finished() noexcept override;
201 :
202 : /** Reset the thread's inline completion budget.
203 :
204 : Called at the start of each posted completion handler to
205 : grant a fresh budget for speculative inline completions.
206 : */
207 : void reset_inline_budget() const noexcept;
208 :
209 : /** Consume one unit of inline budget if available.
210 :
211 : @return True if budget was available and consumed.
212 : */
213 : bool try_consume_inline_budget() const noexcept;
214 :
215 : /** Offset a forthcoming work_finished from work_cleanup.
216 :
217 : Called by descriptor_state when all I/O returned EAGAIN and
218 : no handler will be executed. Must be called from a scheduler
219 : thread.
220 : */
221 : /** Note that an op was parked outside the usual registration path.
222 :
223 : A reactor that builds its poll set from parked ops must rebuild
224 : it; one the kernel tracks needs nothing.
225 : */
226 465 : virtual void notify_reparked() const {}
227 :
228 : void compensating_work_started() const noexcept;
229 :
230 : /** Post an operation whose work is already counted.
231 :
232 : The posting thread touches nothing of the scheduler after this
233 : returns, unlike a @ref post followed by @ref work_finished: once
234 : posted, the operation can complete and let its context be
235 : destroyed.
236 :
237 : @pre work_started() was called for @p op.
238 :
239 : @param op The operation to post.
240 : */
241 : void post_counted(scheduler_op* op) const;
242 :
243 : /** Post completed operations for deferred invocation.
244 :
245 : If called from a thread running this scheduler, operations
246 : go to the thread's private queue (fast path). Otherwise,
247 : operations are added to the global queue under mutex and a
248 : waiter is signaled.
249 :
250 : @pre work_started() must have been called for each operation.
251 :
252 : @param ops Queue of operations to post.
253 : */
254 : void post_deferred_completions(ready_queue& ops) const;
255 :
256 : /** Apply runtime configuration to the scheduler.
257 :
258 : Called by `io_context` after construction. Values that do
259 : not apply to this backend are silently ignored.
260 :
261 : @pre `max_events` is in [ 1, `INT_MAX` ] and `budget_max` is at
262 : most `INT_MAX`; `io_context` validates both.
263 :
264 : @param max_events Event buffer size for epoll/kqueue.
265 : @param budget_init Starting inline completion budget.
266 : @param budget_max Hard ceiling on adaptive budget ramp-up.
267 : @param unassisted Budget when single-threaded.
268 : */
269 : virtual void configure_reactor(
270 : unsigned max_events,
271 : unsigned budget_init,
272 : unsigned budget_max,
273 : unsigned unassisted);
274 :
275 : /// Return the configured initial inline budget.
276 13089 : unsigned inline_budget_initial() const noexcept
277 : {
278 13089 : return inline_budget_initial_;
279 : }
280 :
281 : /// Return true when scheduler locking is disabled (fully-lockless tier).
282 1460 : bool scheduler_locking_disabled() const noexcept override
283 : {
284 1460 : return scheduler_locking_disabled_;
285 : }
286 :
287 4510 : void configure_threading(threading_config cfg) noexcept override
288 : {
289 4510 : scheduler_locking_disabled_ = !cfg.scheduler_locking;
290 : // reactor_io_locking takes effect at descriptor registration (see the
291 : // register_descriptor overrides), not here.
292 4510 : reactor_io_locking_ = cfg.reactor_io_locking;
293 4510 : one_thread_ = cfg.one_thread;
294 4510 : mutex_.set_enabled(cfg.scheduler_locking);
295 4510 : cond_.set_enabled(cfg.scheduler_locking);
296 4510 : }
297 :
298 : protected:
299 : bool scheduler_locking_disabled_ = false;
300 : bool reactor_io_locking_ = true;
301 : bool one_thread_ = false;
302 :
303 4526 : reactor_scheduler() = default;
304 :
305 : /// Destroy, destroying whatever was posted after the drain.
306 : ~reactor_scheduler() override;
307 :
308 : /** Drain completed_ops during shutdown.
309 :
310 : Pops all operations from the global queue and destroys them,
311 : skipping the task sentinel. Signals all waiting threads.
312 : Derived classes call this from their shutdown() override
313 : before performing platform-specific cleanup.
314 : */
315 : void shutdown_drain();
316 :
317 : /// Destroy every queued operation without running it.
318 : void destroy_queued(lock_type& lock) noexcept;
319 :
320 : /// RAII guard that re-inserts the task sentinel after `run_task`.
321 : struct task_cleanup
322 : {
323 : reactor_scheduler const* sched;
324 : lock_type* lock;
325 : context_type& ctx;
326 : ~task_cleanup();
327 : };
328 :
329 : mutable mutex_type mutex_{true};
330 : mutable event_type cond_{true};
331 : mutable ready_queue completed_ops_;
332 : mutable std::atomic<std::int64_t> outstanding_work_{0};
333 : std::atomic<bool> stopped_{false};
334 : mutable std::atomic<bool> task_running_{false};
335 : mutable bool task_interrupted_ = false;
336 :
337 : // Descriptors retired during the running reactor pass (guarded by
338 : // mutex_).
339 : mutable reactor_retirable* retired_ = nullptr;
340 :
341 : /// Settle every descriptor retired before the current pass ended.
342 : /// @pre `lock` holds `mutex_`; it is held again on return.
343 : void settle_retired(lock_type& lock) const;
344 :
345 : // Runtime-configurable reactor tuning parameters.
346 : // Defaults match the library's built-in values.
347 : unsigned max_events_per_poll_ = 128;
348 : unsigned inline_budget_initial_ = 2;
349 : unsigned inline_budget_max_ = 16;
350 : unsigned unassisted_budget_ = 4;
351 :
352 : /// Bit 0 of `state_`: set when the condvar should be signaled.
353 : static constexpr std::size_t signaled_bit = 1;
354 :
355 : /// Increment per waiting thread in `state_`.
356 : static constexpr std::size_t waiter_increment = 2;
357 : mutable std::size_t state_ = 0;
358 :
359 : /// Sentinel op that triggers a reactor poll when dequeued.
360 : struct task_op final : scheduler_op
361 : {
362 : // LCOV_EXCL_START: the sentinel is intercepted by pointer
363 : // identity; its virtuals exist for vtable completeness.
364 : void operator()() override {}
365 : void destroy() override {}
366 : // LCOV_EXCL_STOP
367 : };
368 : task_op task_op_;
369 :
370 : /** Run the platform-specific reactor poll.
371 :
372 : @par Postconditions
373 : `lock` is owned on return, however the poll ended. An
374 : implementation that unlocks around the blocking call owes the
375 : caller a matching re-acquire on every path out, including the
376 : errors it retries rather than reports.
377 : */
378 : virtual void
379 : run_task(lock_type& lock, context_type& ctx, long timeout_us) = 0;
380 :
381 : /// Wake a blocked reactor (e.g. write to eventfd or pipe).
382 : virtual void interrupt_reactor() const = 0;
383 :
384 : /// Wake the reactor whenever the earliest timer changes.
385 : void on_timer_service_attached(timer_service& svc) override;
386 :
387 : private:
388 : struct work_cleanup
389 : {
390 : reactor_scheduler* sched;
391 : lock_type* lock;
392 : context_type& ctx;
393 : ~work_cleanup();
394 : };
395 :
396 : std::size_t do_one(lock_type& lock, long timeout_us, context_type& ctx);
397 :
398 : void signal_all(lock_type& lock) const;
399 : bool maybe_unlock_and_signal_one(lock_type& lock) const;
400 : bool unlock_and_signal_one(lock_type& lock) const;
401 : void clear_signal() const;
402 : void wait_for_signal(lock_type& lock) const;
403 : void wait_for_signal_for(lock_type& lock, long timeout_us) const;
404 : void wake_one_thread_and_unlock(lock_type& lock) const;
405 : };
406 :
407 : /** RAII guard that pushes/pops a scheduler context frame.
408 :
409 : On construction, pushes a new context frame onto the
410 : thread-local stack. On destruction, drains any remaining
411 : private queue items to the global queue and pops the frame.
412 : */
413 : struct reactor_thread_context_guard
414 : {
415 : /// The context frame managed by this guard.
416 : reactor_scheduler_context frame_;
417 :
418 : /// Marks the scheduler innermost for the executor's fast check.
419 : running_scheduler_guard running_;
420 :
421 : /// Construct the guard, pushing a frame for @a sched.
422 13089 : explicit reactor_thread_context_guard(
423 : reactor_scheduler const* sched) noexcept
424 13089 : : frame_(sched, reactor_context_stack.get())
425 13089 : , running_(sched)
426 : {
427 13089 : reactor_context_stack.set(&frame_);
428 13089 : }
429 :
430 : /** Destroy the guard, popping the frame.
431 :
432 : The private queue is empty here by invariant: work_cleanup and
433 : task_cleanup splice it to the global queue after every handler
434 : and every reactor pass.
435 : */
436 13089 : ~reactor_thread_context_guard() noexcept
437 : {
438 13089 : reactor_context_stack.set(frame_.next);
439 13089 : }
440 : };
441 :
442 : // ---- Inline implementations ------------------------------------------------
443 :
444 13089 : inline reactor_scheduler_context::reactor_scheduler_context(
445 13089 : reactor_scheduler const* k, reactor_scheduler_context* n)
446 13089 : : key(k)
447 13089 : , next(n)
448 13089 : , private_outstanding_work(0)
449 13089 : , inline_budget(0)
450 13089 : , inline_budget_max(static_cast<int>(k->inline_budget_initial()))
451 13089 : , unassisted(false)
452 : {
453 13089 : }
454 :
455 : inline void
456 50 : reactor_scheduler::configure_reactor(
457 : unsigned max_events,
458 : unsigned budget_init,
459 : unsigned budget_max,
460 : unsigned unassisted)
461 : {
462 50 : BOOST_COROSIO_ASSERT(
463 : max_events >= 1 &&
464 : max_events <= static_cast<unsigned>((std::numeric_limits<int>::max)()));
465 50 : BOOST_COROSIO_ASSERT(
466 : budget_max <= static_cast<unsigned>((std::numeric_limits<int>::max)()));
467 :
468 : // Clamp initial and unassisted to budget_max.
469 50 : if (budget_init > budget_max)
470 20 : budget_init = budget_max;
471 50 : if (unassisted > budget_max)
472 20 : unassisted = budget_max;
473 :
474 50 : max_events_per_poll_ = max_events;
475 50 : inline_budget_initial_ = budget_init;
476 50 : inline_budget_max_ = budget_max;
477 50 : unassisted_budget_ = unassisted;
478 50 : }
479 :
480 : inline void
481 87185 : reactor_scheduler::reset_inline_budget() const noexcept
482 : {
483 : // When budget is disabled (max==0), all paths below would no-op
484 : // (inline_budget stays 0). Skip the TLS lookup entirely.
485 87185 : if (inline_budget_max_ == 0)
486 58 : return;
487 87127 : if (auto* ctx = reactor_find_context(this))
488 : {
489 : // Cap when no other thread absorbed queued work
490 87127 : if (ctx->unassisted)
491 : {
492 86088 : ctx->inline_budget_max = static_cast<int>(unassisted_budget_);
493 86088 : ctx->inline_budget = static_cast<int>(unassisted_budget_);
494 86088 : return;
495 : }
496 : // Ramp up when previous cycle fully consumed budget.
497 : // max(1, ...) ensures the doubling escapes zero.
498 : // Doubled in a wider type: the cap may be as large as INT_MAX.
499 1039 : if (ctx->inline_budget == 0)
500 : {
501 : long long const doubled =
502 339 : 2LL * (std::max)(1, ctx->inline_budget_max);
503 339 : long long const cap = inline_budget_max_;
504 339 : ctx->inline_budget_max = static_cast<int>((std::min)(doubled, cap));
505 : }
506 700 : else if (ctx->inline_budget < ctx->inline_budget_max)
507 : {
508 234 : ctx->inline_budget_max = static_cast<int>(inline_budget_initial_);
509 : }
510 1039 : ctx->inline_budget = ctx->inline_budget_max;
511 : }
512 : }
513 :
514 : inline bool
515 352506 : reactor_scheduler::try_consume_inline_budget() const noexcept
516 : {
517 352506 : if (inline_budget_max_ == 0)
518 44 : return false;
519 352462 : if (auto* ctx = reactor_find_context(this))
520 : {
521 352445 : if (ctx->inline_budget > 0)
522 : {
523 281693 : --ctx->inline_budget;
524 281693 : return true;
525 : }
526 : }
527 70769 : return false;
528 : }
529 :
530 : inline void
531 3678 : reactor_scheduler::post(std::coroutine_handle<> h) const
532 : {
533 : struct post_handler final : scheduler_op
534 : {
535 : std::coroutine_handle<> h_;
536 :
537 3678 : explicit post_handler(std::coroutine_handle<> h) : h_(h) {}
538 7356 : ~post_handler() override = default;
539 :
540 3662 : void operator()() override
541 : {
542 3662 : auto saved = h_;
543 3662 : delete this;
544 3662 : saved.resume();
545 3662 : }
546 :
547 16 : void destroy() override
548 : {
549 : // A bare handle carries no owner to unwind from: it is
550 : // destroyed directly.
551 16 : auto saved = h_;
552 16 : delete this;
553 16 : saved.destroy();
554 16 : }
555 : };
556 :
557 3678 : auto ph = std::make_unique<post_handler>(h);
558 :
559 3678 : if (auto* ctx = reactor_find_context(this))
560 : {
561 12 : ++ctx->private_outstanding_work;
562 12 : ctx->private_queue.push(ph.release());
563 12 : return;
564 : }
565 :
566 3666 : outstanding_work_.fetch_add(1, std::memory_order_relaxed);
567 :
568 3666 : lock_type lock(mutex_);
569 3666 : completed_ops_.push(ph.release());
570 3666 : wake_one_thread_and_unlock(lock);
571 3678 : }
572 :
573 : inline void
574 94782 : reactor_scheduler::post(scheduler_op* h) const
575 : {
576 94782 : if (auto* ctx = reactor_find_context(this))
577 : {
578 93270 : ++ctx->private_outstanding_work;
579 93270 : ctx->private_queue.push(h);
580 93270 : return;
581 : }
582 :
583 1512 : outstanding_work_.fetch_add(1, std::memory_order_relaxed);
584 :
585 1512 : lock_type lock(mutex_);
586 1512 : completed_ops_.push(h);
587 1512 : wake_one_thread_and_unlock(lock);
588 1512 : }
589 :
590 : inline void
591 236794 : reactor_scheduler::post(capy::continuation& c) const
592 : {
593 236794 : if (auto* ctx = reactor_find_context(this))
594 : {
595 204508 : ++ctx->private_outstanding_work;
596 204508 : ctx->private_queue.push(c);
597 204508 : return;
598 : }
599 :
600 32286 : outstanding_work_.fetch_add(1, std::memory_order_relaxed);
601 :
602 32286 : lock_type lock(mutex_);
603 32286 : completed_ops_.push(c);
604 32286 : wake_one_thread_and_unlock(lock);
605 32286 : }
606 :
607 : inline bool
608 23781 : reactor_scheduler::running_in_this_thread() const noexcept
609 : {
610 23781 : return reactor_find_context(this) != nullptr;
611 : }
612 :
613 : inline void
614 8401 : reactor_scheduler::stop()
615 : {
616 8401 : lock_type lock(mutex_);
617 8401 : if (!stopped_.load(std::memory_order_acquire))
618 : {
619 7332 : stopped_.store(true, std::memory_order_release);
620 7332 : signal_all(lock);
621 7332 : interrupt_reactor();
622 : }
623 8401 : }
624 :
625 : inline bool
626 3569 : reactor_scheduler::stopped() const noexcept
627 : {
628 3569 : return stopped_.load(std::memory_order_acquire);
629 : }
630 :
631 : inline void
632 5679 : reactor_scheduler::restart()
633 : {
634 5679 : stopped_.store(false, std::memory_order_release);
635 5679 : }
636 :
637 : inline std::size_t
638 6496 : reactor_scheduler::run()
639 : {
640 12992 : if (outstanding_work_.load(std::memory_order_acquire) == 0)
641 : {
642 288 : stop();
643 288 : return 0;
644 : }
645 :
646 6208 : reactor_thread_context_guard ctx(this);
647 6208 : lock_type lock(mutex_);
648 :
649 6208 : std::size_t n = 0;
650 : for (;;)
651 : {
652 369666 : if (!do_one(lock, -1, ctx.frame_))
653 6205 : break;
654 363458 : if (n != (std::numeric_limits<std::size_t>::max)())
655 363458 : ++n;
656 363458 : if (!lock.owns_lock())
657 84207 : lock.lock();
658 : }
659 6205 : return n;
660 6211 : }
661 :
662 : inline std::size_t
663 128 : reactor_scheduler::run_one()
664 : {
665 256 : if (outstanding_work_.load(std::memory_order_acquire) == 0)
666 : {
667 3 : stop();
668 3 : return 0;
669 : }
670 :
671 125 : reactor_thread_context_guard ctx(this);
672 125 : lock_type lock(mutex_);
673 125 : return do_one(lock, -1, ctx.frame_);
674 125 : }
675 :
676 : inline std::size_t
677 6187 : reactor_scheduler::wait_one(long usec)
678 : {
679 12374 : if (outstanding_work_.load(std::memory_order_acquire) == 0)
680 : {
681 808 : stop();
682 808 : return 0;
683 : }
684 :
685 5379 : reactor_thread_context_guard ctx(this);
686 5379 : lock_type lock(mutex_);
687 5379 : return do_one(lock, usec, ctx.frame_);
688 5379 : }
689 :
690 : inline std::size_t
691 1349 : reactor_scheduler::poll()
692 : {
693 2698 : if (outstanding_work_.load(std::memory_order_acquire) == 0)
694 : {
695 29 : stop();
696 29 : return 0;
697 : }
698 :
699 1320 : reactor_thread_context_guard ctx(this);
700 1320 : lock_type lock(mutex_);
701 :
702 1320 : std::size_t n = 0;
703 : for (;;)
704 : {
705 9344 : if (!do_one(lock, 0, ctx.frame_))
706 1320 : break;
707 8024 : if (n != (std::numeric_limits<std::size_t>::max)())
708 8024 : ++n;
709 8024 : if (!lock.owns_lock())
710 8022 : lock.lock();
711 : }
712 1320 : return n;
713 1320 : }
714 :
715 : inline std::size_t
716 62 : reactor_scheduler::poll_one()
717 : {
718 124 : if (outstanding_work_.load(std::memory_order_acquire) == 0)
719 : {
720 5 : stop();
721 5 : return 0;
722 : }
723 :
724 57 : reactor_thread_context_guard ctx(this);
725 57 : lock_type lock(mutex_);
726 57 : return do_one(lock, 0, ctx.frame_);
727 57 : }
728 :
729 : inline void
730 66905 : reactor_scheduler::work_started() noexcept
731 : {
732 66905 : outstanding_work_.fetch_add(1, std::memory_order_relaxed);
733 66905 : }
734 :
735 : inline void
736 111566 : reactor_scheduler::work_finished() noexcept
737 : {
738 223132 : if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
739 7203 : stop();
740 111566 : }
741 :
742 : inline void
743 31188 : reactor_scheduler::compensating_work_started() const noexcept
744 : {
745 31188 : auto* ctx = reactor_find_context(this);
746 31188 : if (ctx)
747 31186 : ++ctx->private_outstanding_work;
748 31188 : }
749 :
750 : inline void
751 2004 : reactor_scheduler::post_counted(scheduler_op* op) const
752 : {
753 2004 : if (auto* ctx = reactor_find_context(this))
754 : {
755 610 : ctx->private_queue.push(op);
756 610 : return;
757 : }
758 :
759 1394 : lock_type lock(mutex_);
760 1394 : completed_ops_.push(op);
761 1394 : wake_one_thread_and_unlock(lock);
762 1394 : }
763 :
764 : inline void
765 15934 : reactor_scheduler::post_deferred_completions(ready_queue& ops) const
766 : {
767 15934 : if (ops.empty())
768 15934 : return;
769 :
770 2 : if (auto* ctx = reactor_find_context(this))
771 : {
772 2 : ctx->private_queue.splice(ops);
773 2 : return;
774 : }
775 :
776 MIS 0 : lock_type lock(mutex_);
777 0 : completed_ops_.splice(ops);
778 0 : wake_one_thread_and_unlock(lock);
779 0 : }
780 :
781 : inline void
782 HIT 23032 : reactor_scheduler::retire_descriptor(
783 : reactor_retirable& d, object_ref keep) const
784 : {
785 23032 : lock_type lock(mutex_);
786 23032 : if (!task_running_.load(std::memory_order_relaxed))
787 : {
788 : // No pass can hold an event, but an earlier one may have
789 : // queued d.
790 17769 : d.hand_off(keep);
791 17769 : return;
792 : }
793 : // Already parked for this pass: the held reference suffices.
794 5263 : if (d.retired_ref_)
795 117 : return;
796 5146 : d.retired_ref_ = std::move(keep);
797 5146 : d.retired_next_ = retired_;
798 5146 : retired_ = &d;
799 23032 : }
800 :
801 : inline void
802 286761 : reactor_scheduler::settle_retired(lock_type& lock) const
803 : {
804 : // Handed off under the lock, since a later pass may retire the same
805 : // descriptor again as soon as it is released. A reference that is
806 : // not handed off may be the owner's last, and its release recycles
807 : // through the pool mutex, so it is dropped with the lock released.
808 286761 : reactor_retirable* dropped = nullptr;
809 291907 : while (auto* d = retired_)
810 : {
811 5146 : retired_ = d->retired_next_;
812 5146 : d->retired_next_ = nullptr;
813 5146 : auto keep = std::move(d->retired_ref_);
814 5146 : d->hand_off(keep);
815 : // A drop already pending keeps the owner alive, so this one
816 : // cannot be the last and is released here.
817 5146 : if (!keep || d->dropped_ref_)
818 376 : continue;
819 4770 : d->dropped_ref_ = std::move(keep);
820 4770 : d->dropped_next_ = dropped;
821 4770 : dropped = d;
822 10292 : }
823 291531 : while (auto* d = dropped)
824 : {
825 4770 : dropped = d->dropped_next_;
826 4770 : d->dropped_next_ = nullptr;
827 4770 : auto keep = std::move(d->dropped_ref_);
828 4770 : lock.unlock();
829 4770 : keep.reset();
830 4770 : lock.lock();
831 4770 : }
832 286761 : }
833 :
834 : inline void
835 393 : reactor_scheduler::on_timer_service_attached(timer_service& svc)
836 : {
837 393 : svc.set_on_earliest_changed(timer_service::callback(this, [](void* p) {
838 3212 : static_cast<reactor_scheduler*>(p)->interrupt_reactor();
839 3212 : }));
840 393 : }
841 :
842 : inline void
843 4510 : reactor_scheduler::shutdown_drain()
844 : {
845 4510 : wait_cancels_posting();
846 :
847 4510 : lock_type lock(mutex_);
848 4510 : settle_retired(lock);
849 4510 : destroy_queued(lock);
850 4510 : signal_all(lock);
851 4510 : }
852 :
853 4526 : inline reactor_scheduler::~reactor_scheduler()
854 : {
855 : // Services give up their work in shutdown(), but anything posted
856 : // after the drain, such as from a destructor, is still destroyed.
857 4526 : lock_type lock(mutex_);
858 4526 : destroy_queued(lock);
859 4526 : }
860 :
861 : inline void
862 9036 : reactor_scheduler::destroy_queued(lock_type& lock) noexcept
863 : {
864 22928 : while (auto e = completed_ops_.pop())
865 : {
866 13892 : if (ready_is_continuation(e))
867 : {
868 7843 : lock.unlock();
869 7843 : if (auto* c = ready_as_cont(e); c->h)
870 7843 : capy::abandon(*c);
871 7843 : lock.lock();
872 : }
873 : else
874 : {
875 6049 : auto* op = ready_as_op(e);
876 6049 : if (op == &task_op_)
877 4507 : continue;
878 1542 : lock.unlock();
879 1542 : op->destroy();
880 1542 : lock.lock();
881 : }
882 13892 : }
883 9036 : }
884 :
885 : inline void
886 11842 : reactor_scheduler::signal_all(lock_type&) const
887 : {
888 11842 : state_ |= signaled_bit;
889 11842 : cond_.notify_all();
890 11842 : }
891 :
892 : inline bool
893 42681 : reactor_scheduler::maybe_unlock_and_signal_one(lock_type& lock) const
894 : {
895 42681 : state_ |= signaled_bit;
896 42681 : if (state_ > signaled_bit)
897 : {
898 : // Signalled before unlocking: a post from another context's
899 : // thread may be the last touch of this scheduler before the
900 : // posted work runs, finishes and lets it be destroyed.
901 178 : cond_.notify_one();
902 178 : lock.unlock();
903 178 : return true;
904 : }
905 42503 : return false;
906 : }
907 :
908 : inline bool
909 620857 : reactor_scheduler::unlock_and_signal_one(lock_type& lock) const
910 : {
911 620857 : state_ |= signaled_bit;
912 620857 : bool have_waiters = state_ > signaled_bit;
913 620857 : lock.unlock();
914 620857 : if (have_waiters)
915 4194 : cond_.notify_one();
916 620857 : return have_waiters;
917 : }
918 :
919 : inline void
920 791 : reactor_scheduler::clear_signal() const
921 : {
922 791 : state_ &= ~signaled_bit;
923 791 : }
924 :
925 : inline void
926 762 : reactor_scheduler::wait_for_signal(lock_type& lock) const
927 : {
928 1590 : while ((state_ & signaled_bit) == 0)
929 : {
930 828 : state_ += waiter_increment;
931 828 : cond_.wait(lock);
932 828 : state_ -= waiter_increment;
933 : }
934 762 : }
935 :
936 : inline void
937 29 : reactor_scheduler::wait_for_signal_for(lock_type& lock, long timeout_us) const
938 : {
939 29 : if ((state_ & signaled_bit) == 0)
940 : {
941 29 : state_ += waiter_increment;
942 29 : cond_.wait_for(lock, std::chrono::microseconds(timeout_us));
943 29 : state_ -= waiter_increment;
944 : }
945 29 : }
946 :
947 : inline void
948 38858 : reactor_scheduler::wake_one_thread_and_unlock(lock_type& lock) const
949 : {
950 38858 : if (maybe_unlock_and_signal_one(lock))
951 159 : return;
952 :
953 38699 : if (task_running_.load(std::memory_order_relaxed) && !task_interrupted_)
954 : {
955 1836 : task_interrupted_ = true;
956 : // Under the lock, for the same reason as the signal above.
957 1836 : interrupt_reactor();
958 1836 : lock.unlock();
959 : }
960 : else
961 : {
962 36863 : lock.unlock();
963 : }
964 : }
965 :
966 374354 : inline reactor_scheduler::work_cleanup::~work_cleanup()
967 : {
968 374354 : std::int64_t produced = ctx.private_outstanding_work;
969 374354 : if (produced > 1)
970 1000 : sched->outstanding_work_.fetch_add(
971 : produced - 1, std::memory_order_relaxed);
972 373354 : else if (produced < 1)
973 64946 : sched->work_finished();
974 374354 : ctx.private_outstanding_work = 0;
975 :
976 374354 : if (!ctx.private_queue.empty())
977 : {
978 279555 : lock->lock();
979 279555 : sched->completed_ops_.splice(ctx.private_queue);
980 : }
981 374354 : }
982 :
983 282254 : inline reactor_scheduler::task_cleanup::~task_cleanup()
984 : {
985 282254 : if (ctx.private_outstanding_work > 0)
986 : {
987 9598 : sched->outstanding_work_.fetch_add(
988 9598 : ctx.private_outstanding_work, std::memory_order_relaxed);
989 9598 : ctx.private_outstanding_work = 0;
990 : }
991 :
992 282254 : if (!ctx.private_queue.empty())
993 : {
994 9598 : if (!lock->owns_lock())
995 MIS 0 : lock->lock();
996 HIT 9598 : sched->completed_ops_.splice(ctx.private_queue);
997 : }
998 282254 : }
999 :
1000 : inline std::size_t
1001 384571 : reactor_scheduler::do_one(lock_type& lock, long timeout_us, context_type& ctx)
1002 : {
1003 : for (;;)
1004 : {
1005 663788 : if (stopped_.load(std::memory_order_acquire))
1006 6380 : return 0;
1007 :
1008 657408 : auto const e = completed_ops_.pop();
1009 657408 : scheduler_op* op = ready_is_continuation(e) ? nullptr : ready_as_op(e);
1010 :
1011 : // Handle reactor sentinel — time to poll for I/O
1012 657408 : if (op == &task_op_)
1013 : {
1014 282260 : bool more_handlers = !completed_ops_.empty();
1015 :
1016 316150 : if (!more_handlers &&
1017 67780 : outstanding_work_.load(std::memory_order_acquire) == 0)
1018 : {
1019 6 : completed_ops_.push(&task_op_);
1020 6 : return 0;
1021 : }
1022 :
1023 282254 : long task_timeout_us = more_handlers ? 0 : timeout_us;
1024 282254 : task_interrupted_ = task_timeout_us == 0;
1025 282254 : task_running_.store(true, std::memory_order_release);
1026 :
1027 : // Wake a peer to take the pending handlers while this thread
1028 : // polls the reactor; skipped when one_thread_ (no peer exists).
1029 282254 : if (more_handlers && !one_thread_)
1030 248359 : unlock_and_signal_one(lock);
1031 :
1032 : try
1033 : {
1034 282254 : run_task(lock, ctx, task_timeout_us);
1035 : }
1036 3 : catch (...)
1037 : {
1038 3 : task_running_.store(false, std::memory_order_relaxed);
1039 3 : throw;
1040 3 : }
1041 :
1042 282251 : task_running_.store(false, std::memory_order_relaxed);
1043 282251 : bool const reaped = !completed_ops_.empty();
1044 282251 : completed_ops_.push(&task_op_);
1045 282251 : settle_retired(lock);
1046 :
1047 : // wait_one() returns after one pass; poll() and poll_one()
1048 : // return after a pass that reaps nothing. Either way, wake a
1049 : // parked peer to take the sentinel.
1050 282251 : if (timeout_us > 0 || (timeout_us == 0 && !reaped))
1051 : {
1052 3825 : if (!one_thread_)
1053 3823 : maybe_unlock_and_signal_one(lock);
1054 3825 : return 0;
1055 : }
1056 278426 : continue;
1057 278426 : }
1058 :
1059 : // Handle ready entry (op or continuation)
1060 375148 : if (e != nullptr)
1061 : {
1062 374354 : bool more = !completed_ops_.empty();
1063 :
1064 374354 : if (more && !one_thread_)
1065 : {
1066 : // Wake a peer for the remaining work; unassisted if none
1067 : // was parked to take it.
1068 372498 : ctx.unassisted = !unlock_and_signal_one(lock);
1069 : }
1070 : else
1071 : {
1072 : // No peer to wake (one_thread_, or nothing more queued).
1073 1856 : ctx.unassisted = more;
1074 1856 : lock.unlock();
1075 : }
1076 :
1077 374354 : [[maybe_unused]] work_cleanup on_exit{this, &lock, ctx};
1078 :
1079 374354 : if (ready_is_continuation(e))
1080 228951 : ready_as_cont(e)->h.resume();
1081 : else
1082 145403 : (*op)();
1083 374354 : return 1;
1084 374354 : }
1085 :
1086 1588 : if (outstanding_work_.load(std::memory_order_acquire) == 0 ||
1087 : timeout_us == 0)
1088 3 : return 0;
1089 :
1090 791 : clear_signal();
1091 791 : if (timeout_us < 0)
1092 762 : wait_for_signal(lock);
1093 : else
1094 29 : wait_for_signal_for(lock, timeout_us);
1095 279217 : }
1096 : }
1097 :
1098 : } // namespace boost::corosio::detail
1099 :
1100 : #endif // BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SCHEDULER_HPP
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