include/boost/corosio/native/detail/reactor/reactor_scheduler.hpp

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reactor_scheduler.hpp

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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/capy/ex/execution_context.hpp>
15
16		#include <boost/corosio/detail/ready_queue.hpp>
17		#include <boost/corosio/detail/scheduler.hpp>
18		#include <boost/corosio/detail/scheduler_op.hpp>
19		#include <boost/corosio/detail/thread_local_ptr.hpp>
20
21		#include <atomic>
22		#include <chrono>
23		#include <coroutine>
24		#include <cstddef>
25		#include <cstdint>
26		#include <limits>
27		#include <memory>
28		#include <stdexcept>
29
30		#include <boost/corosio/detail/conditionally_enabled_mutex.hpp>
31		#include <boost/corosio/detail/conditionally_enabled_event.hpp>
32
33		namespace boost::corosio::detail {
34
35		// Forward declarations
36		class reactor_scheduler;
37		class timer_service;
38
39		/** Per-thread state for a reactor scheduler.
40
41		Each thread running a scheduler's event loop has one of these
42		on a thread-local stack. It holds a private work queue and
43		inline completion budget for speculative I/O fast paths.
44		*/
45		struct BOOST_COROSIO_SYMBOL_VISIBLE reactor_scheduler_context
46		{
47		/// Scheduler this context belongs to.
48		reactor_scheduler const* key;
49
50		/// Next context frame on this thread's stack.
51		reactor_scheduler_context* next;
52
53		/// Private work queue for reduced contention.
54		ready_queue private_queue;
55
56		/// Unflushed work count for the private queue.
57		std::int64_t private_outstanding_work;
58
59		/// Remaining inline completions allowed this cycle.
60		int inline_budget;
61
62		/// Maximum inline budget (adaptive, 2-16).
63		int inline_budget_max;
64
65		/// True if no other thread absorbed queued work last cycle.
66		bool unassisted;
67
68		/// Construct a context frame linked to @a n.
69		reactor_scheduler_context(
70		reactor_scheduler const* k,
71		reactor_scheduler_context* n);
72		};
73
74		/// Thread-local context stack for reactor schedulers.
75		inline thread_local_ptr<reactor_scheduler_context> reactor_context_stack;
76
77		/// Find the context frame for a scheduler on this thread.
78		inline reactor_scheduler_context*
79	860211x	reactor_find_context(reactor_scheduler const* self) noexcept
80		{
81	860211x	for (auto* c = reactor_context_stack.get(); c != nullptr; c = c->next)
82		{
83	845291x	if (c->key == self)
84	845291x	return c;
85		}
86	14920x	return nullptr;
87		}
88
89		/// Flush private work count to global counter.
90		inline void
91	✗	reactor_flush_private_work(
92		reactor_scheduler_context* ctx,
93		std::atomic<std::int64_t>& outstanding_work) noexcept
94		{
95	✗	if (ctx && ctx->private_outstanding_work > 0)
96		{
97	✗	outstanding_work.fetch_add(
98		ctx->private_outstanding_work, std::memory_order_relaxed);
99	✗	ctx->private_outstanding_work = 0;
100		}
101	✗	}
102
103		/** Drain private queue to global queue, flushing work count first.
104
105		@return True if any ops were drained.
106		*/
107		inline bool
108	10x	reactor_drain_private_queue(
109		reactor_scheduler_context* ctx,
110		std::atomic<std::int64_t>& outstanding_work,
111		ready_queue& completed_ops) noexcept
112		{
113	10x	if (!ctx \|\| ctx->private_queue.empty())
114	10x	return false;
115
116	✗	reactor_flush_private_work(ctx, outstanding_work);
117	✗	completed_ops.splice(ctx->private_queue);
118	✗	return true;
119		}
120
121		/** Non-template base for reactor-backed scheduler implementations.
122
123		Provides the complete threading model shared by epoll, kqueue,
124		and select schedulers: signal state machine, inline completion
125		budget, work counting, run/poll methods, and the do_one event
126		loop.
127
128		Derived classes provide platform-specific hooks by overriding:
129		- `run_task(lock, ctx)` to run the reactor poll
130		- `interrupt_reactor()` to wake a blocked reactor
131
132		De-templated from the original CRTP design to eliminate
133		duplicate instantiations when multiple backends are compiled
134		into the same binary. Virtual dispatch for run_task (called
135		once per reactor cycle, before a blocking syscall) has
136		negligible overhead.
137
138		@par Thread Safety
139		All public member functions are thread-safe.
140		*/
141		class reactor_scheduler
142		: public scheduler
143		, public capy::execution_context::service
144		{
145		public:
146		using key_type = scheduler;
147		using context_type = reactor_scheduler_context;
148		using mutex_type = conditionally_enabled_mutex;
149		using lock_type = mutex_type::scoped_lock;
150		using event_type = conditionally_enabled_event;
151
152		/// Post a coroutine for deferred execution.
153		void post(std::coroutine_handle<> h) const override;
154
155		/// Post a scheduler operation for deferred execution.
156		void post(scheduler_op* h) const override;
157
158		/// Post a continuation for deferred execution.
159		void post(capy::continuation&) const override;
160
161		/// Return true if called from a thread running this scheduler.
162		bool running_in_this_thread() const noexcept override;
163
164		/// Request the scheduler to stop dispatching handlers.
165		void stop() override;
166
167		/// Return true if the scheduler has been stopped.
168		bool stopped() const noexcept override;
169
170		/// Reset the stopped state so `run()` can resume.
171		void restart() override;
172
173		/// Run the event loop until no work remains.
174		std::size_t run() override;
175
176		/// Run until one handler completes or no work remains.
177		std::size_t run_one() override;
178
179		/// Run until one handler completes or @a usec elapses.
180		std::size_t wait_one(long usec) override;
181
182		/// Run ready handlers without blocking.
183		std::size_t poll() override;
184
185		/// Run at most one ready handler without blocking.
186		std::size_t poll_one() override;
187
188		/// Increment the outstanding work count.
189		void work_started() noexcept override;
190
191		/// Decrement the outstanding work count, stopping on zero.
192		void work_finished() noexcept override;
193
194		/** Reset the thread's inline completion budget.
195
196		Called at the start of each posted completion handler to
197		grant a fresh budget for speculative inline completions.
198		*/
199		void reset_inline_budget() const noexcept;
200
201		/** Consume one unit of inline budget if available.
202
203		@return True if budget was available and consumed.
204		*/
205		bool try_consume_inline_budget() const noexcept;
206
207		/** Offset a forthcoming work_finished from work_cleanup.
208
209		Called by descriptor_state when all I/O returned EAGAIN and
210		no handler will be executed. Must be called from a scheduler
211		thread.
212		*/
213		void compensating_work_started() const noexcept;
214
215		/** Drain work from thread context's private queue to global queue.
216
217		Flushes private work count to the global counter, then
218		transfers the queue under mutex protection.
219
220		@param queue The private queue to drain.
221		@param count Private work count to flush before draining.
222		*/
223		void drain_thread_queue(ready_queue& queue, std::int64_t count) const;
224
225		/** Post completed operations for deferred invocation.
226
227		If called from a thread running this scheduler, operations
228		go to the thread's private queue (fast path). Otherwise,
229		operations are added to the global queue under mutex and a
230		waiter is signaled.
231
232		@par Preconditions
233		work_started() must have been called for each operation.
234
235		@param ops Queue of operations to post.
236		*/
237		void post_deferred_completions(ready_queue& ops) const;
238
239		/** Apply runtime configuration to the scheduler.
240
241		Called by `io_context` after construction. Values that do
242		not apply to this backend are silently ignored.
243
244		@param max_events Event buffer size for epoll/kqueue.
245		@param budget_init Starting inline completion budget.
246		@param budget_max Hard ceiling on adaptive budget ramp-up.
247		@param unassisted Budget when single-threaded.
248		*/
249		virtual void configure_reactor(
250		unsigned max_events,
251		unsigned budget_init,
252		unsigned budget_max,
253		unsigned unassisted);
254
255		/// Return the configured initial inline budget.
256	918x	unsigned inline_budget_initial() const noexcept
257		{
258	918x	return inline_budget_initial_;
259		}
260
261		/// Return true when scheduler locking is disabled (fully-lockless tier).
262	162x	bool scheduler_locking_disabled() const noexcept override
263		{
264	162x	return scheduler_locking_disabled_;
265		}
266
267	1219x	void configure_threading(threading_config cfg) noexcept override
268		{
269	1219x	scheduler_locking_disabled_ = !cfg.scheduler_locking;
270		// reactor_io_locking takes effect at descriptor registration (see the
271		// register_descriptor overrides), not here.
272	1219x	reactor_io_locking_ = cfg.reactor_io_locking;
273	1219x	one_thread_ = cfg.one_thread;
274	1219x	mutex_.set_enabled(cfg.scheduler_locking);
275	1219x	cond_.set_enabled(cfg.scheduler_locking);
276	1219x	}
277
278		protected:
279		timer_service* timer_svc_ = nullptr;
280		bool scheduler_locking_disabled_ = false;
281		bool reactor_io_locking_ = true;
282		bool one_thread_ = false;
283
284	1219x	reactor_scheduler() = default;
285
286		/** Drain completed_ops during shutdown.
287
288		Pops all operations from the global queue and destroys them,
289		skipping the task sentinel. Signals all waiting threads.
290		Derived classes call this from their shutdown() override
291		before performing platform-specific cleanup.
292		*/
293		void shutdown_drain();
294
295		/// RAII guard that re-inserts the task sentinel after `run_task`.
296		struct task_cleanup
297		{
298		reactor_scheduler const* sched;
299		lock_type* lock;
300		context_type* ctx;
301		~task_cleanup();
302		};
303
304		mutable mutex_type mutex_{true};
305		mutable event_type cond_{true};
306		mutable ready_queue completed_ops_;
307		mutable std::atomic<std::int64_t> outstanding_work_{0};
308		std::atomic<bool> stopped_{false};
309		mutable std::atomic<bool> task_running_{false};
310		mutable bool task_interrupted_ = false;
311
312		// Runtime-configurable reactor tuning parameters.
313		// Defaults match the library's built-in values.
314		unsigned max_events_per_poll_ = 128;
315		unsigned inline_budget_initial_ = 2;
316		unsigned inline_budget_max_ = 16;
317		unsigned unassisted_budget_ = 4;
318
319		/// Bit 0 of `state_`: set when the condvar should be signaled.
320		static constexpr std::size_t signaled_bit = 1;
321
322		/// Increment per waiting thread in `state_`.
323		static constexpr std::size_t waiter_increment = 2;
324		mutable std::size_t state_ = 0;
325
326		/// Sentinel op that triggers a reactor poll when dequeued.
327		struct task_op final : scheduler_op
328		{
329	✗	void operator()() override {}
330	✗	void destroy() override {}
331		};
332		task_op task_op_;
333
334		/// Run the platform-specific reactor poll.
335		virtual void
336		run_task(lock_type& lock, context_type* ctx,
337		long timeout_us) = 0;
338
339		/// Wake a blocked reactor (e.g. write to eventfd or pipe).
340		virtual void interrupt_reactor() const = 0;
341
342		private:
343		struct work_cleanup
344		{
345		reactor_scheduler* sched;
346		lock_type* lock;
347		context_type* ctx;
348		~work_cleanup();
349		};
350
351		std::size_t do_one(
352		lock_type& lock, long timeout_us, context_type* ctx);
353
354		void signal_all(lock_type& lock) const;
355		bool maybe_unlock_and_signal_one(lock_type& lock) const;
356		bool unlock_and_signal_one(lock_type& lock) const;
357		void clear_signal() const;
358		void wait_for_signal(lock_type& lock) const;
359		void wait_for_signal_for(
360		lock_type& lock, long timeout_us) const;
361		void wake_one_thread_and_unlock(lock_type& lock) const;
362		};
363
364		/** RAII guard that pushes/pops a scheduler context frame.
365
366		On construction, pushes a new context frame onto the
367		thread-local stack. On destruction, drains any remaining
368		private queue items to the global queue and pops the frame.
369		*/
370		struct reactor_thread_context_guard
371		{
372		/// The context frame managed by this guard.
373		reactor_scheduler_context frame_;
374
375		/// Construct the guard, pushing a frame for @a sched.
376	918x	explicit reactor_thread_context_guard(
377		reactor_scheduler const* sched) noexcept
378	918x	: frame_(sched, reactor_context_stack.get())
379		{
380	918x	reactor_context_stack.set(&frame_);
381	918x	}
382
383		/// Destroy the guard, draining private work and popping the frame.
384	918x	~reactor_thread_context_guard() noexcept
385		{
386	918x	if (!frame_.private_queue.empty())
387	✗	frame_.key->drain_thread_queue(
388	✗	frame_.private_queue, frame_.private_outstanding_work);
389	918x	reactor_context_stack.set(frame_.next);
390	918x	}
391		};
392
393		// ---- Inline implementations ------------------------------------------------
394
395		inline
396	918x	reactor_scheduler_context::reactor_scheduler_context(
397		reactor_scheduler const* k,
398	918x	reactor_scheduler_context* n)
399	918x	: key(k)
400	918x	, next(n)
401	918x	, private_outstanding_work(0)
402	918x	, inline_budget(0)
403	918x	, inline_budget_max(
404	918x	static_cast<int>(k->inline_budget_initial()))
405	918x	, unassisted(false)
406		{
407	918x	}
408
409		inline void
410	25x	reactor_scheduler::configure_reactor(
411		unsigned max_events,
412		unsigned budget_init,
413		unsigned budget_max,
414		unsigned unassisted)
415		{
416	48x	if (max_events < 1 \|\|
417	23x	max_events > static_cast<unsigned>(std::numeric_limits<int>::max()))
418		throw std::out_of_range(
419	2x	"max_events_per_poll must be in [1, INT_MAX]");
420	23x	if (budget_max > static_cast<unsigned>(std::numeric_limits<int>::max()))
421		throw std::out_of_range(
422	✗	"inline_budget_max must be in [0, INT_MAX]");
423
424		// Clamp initial and unassisted to budget_max.
425	23x	if (budget_init > budget_max)
426	2x	budget_init = budget_max;
427	23x	if (unassisted > budget_max)
428	2x	unassisted = budget_max;
429
430	23x	max_events_per_poll_ = max_events;
431	23x	inline_budget_initial_ = budget_init;
432	23x	inline_budget_max_ = budget_max;
433	23x	unassisted_budget_ = unassisted;
434	23x	}
435
436		inline void
437	96105x	reactor_scheduler::reset_inline_budget() const noexcept
438		{
439		// When budget is disabled (max==0), all paths below would no-op
440		// (inline_budget stays 0). Skip the TLS lookup entirely.
441	96105x	if (inline_budget_max_ == 0)
442	✗	return;
443	96105x	if (auto* ctx = reactor_find_context(this))
444		{
445		// Cap when no other thread absorbed queued work
446	96105x	if (ctx->unassisted)
447		{
448	96105x	ctx->inline_budget_max =
449	96105x	static_cast<int>(unassisted_budget_);
450	96105x	ctx->inline_budget =
451	96105x	static_cast<int>(unassisted_budget_);
452	96105x	return;
453		}
454		// Ramp up when previous cycle fully consumed budget.
455		// max(1, ...) ensures the doubling escapes zero.
456	✗	if (ctx->inline_budget == 0)
457	✗	ctx->inline_budget_max = (std::min)(
458	✗	(std::max)(1, ctx->inline_budget_max) * 2,
459	✗	static_cast<int>(inline_budget_max_));
460	✗	else if (ctx->inline_budget < ctx->inline_budget_max)
461	✗	ctx->inline_budget_max =
462	✗	static_cast<int>(inline_budget_initial_);
463	✗	ctx->inline_budget = ctx->inline_budget_max;
464		}
465		}
466
467		inline bool
468	408241x	reactor_scheduler::try_consume_inline_budget() const noexcept
469		{
470	408241x	if (inline_budget_max_ == 0)
471	✗	return false;
472	408241x	if (auto* ctx = reactor_find_context(this))
473		{
474	408241x	if (ctx->inline_budget > 0)
475		{
476	326552x	--ctx->inline_budget;
477	326552x	return true;
478		}
479		}
480	81689x	return false;
481		}
482
483		inline void
484	3686x	reactor_scheduler::post(std::coroutine_handle<> h) const
485		{
486		struct post_handler final : scheduler_op
487		{
488		std::coroutine_handle<> h_;
489
490	3686x	explicit post_handler(std::coroutine_handle<> h) : h_(h) {}
491	7372x	~post_handler() override = default;
492
493	3674x	void operator()() override
494		{
495	3674x	auto saved = h_;
496	3674x	delete this;
497	3674x	saved.resume();
498	3674x	}
499
500	12x	void destroy() override
501		{
502	12x	auto saved = h_;
503	12x	delete this;
504	12x	saved.destroy();
505	12x	}
506		};
507
508	3686x	auto ph = std::make_unique<post_handler>(h);
509
510	3686x	if (auto* ctx = reactor_find_context(this))
511		{
512	26x	++ctx->private_outstanding_work;
513	26x	ctx->private_queue.push(ph.release());
514	26x	return;
515		}
516
517	3660x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
518
519	3660x	lock_type lock(mutex_);
520	3660x	completed_ops_.push(ph.release());
521	3660x	wake_one_thread_and_unlock(lock);
522	3686x	}
523
524		inline void
525	91271x	reactor_scheduler::post(scheduler_op* h) const
526		{
527	91271x	if (auto* ctx = reactor_find_context(this))
528		{
529	90883x	++ctx->private_outstanding_work;
530	90883x	ctx->private_queue.push(h);
531	90883x	return;
532		}
533
534	388x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
535
536	388x	lock_type lock(mutex_);
537	388x	completed_ops_.push(h);
538	388x	wake_one_thread_and_unlock(lock);
539	388x	}
540
541		inline void
542	15094x	reactor_scheduler::post(capy::continuation& c) const
543		{
544	15094x	if (auto* ctx = reactor_find_context(this))
545		{
546	9656x	++ctx->private_outstanding_work;
547	9656x	ctx->private_queue.push(c);
548	9656x	return;
549		}
550
551	5438x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
552
553	5438x	lock_type lock(mutex_);
554	5438x	completed_ops_.push(c);
555	5438x	wake_one_thread_and_unlock(lock);
556	5438x	}
557
558		inline bool
559	6109x	reactor_scheduler::running_in_this_thread() const noexcept
560		{
561	6109x	return reactor_find_context(this) != nullptr;
562		}
563
564		inline void
565	910x	reactor_scheduler::stop()
566		{
567	910x	lock_type lock(mutex_);
568	910x	if (!stopped_.load(std::memory_order_acquire))
569		{
570	846x	stopped_.store(true, std::memory_order_release);
571	846x	signal_all(lock);
572	846x	interrupt_reactor();
573		}
574	910x	}
575
576		inline bool
577	90x	reactor_scheduler::stopped() const noexcept
578		{
579	90x	return stopped_.load(std::memory_order_acquire);
580		}
581
582		inline void
583	177x	reactor_scheduler::restart()
584		{
585	177x	stopped_.store(false, std::memory_order_release);
586	177x	}
587
588		inline std::size_t
589	890x	reactor_scheduler::run()
590		{
591	1780x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
592		{
593	56x	stop();
594	56x	return 0;
595		}
596
597	834x	reactor_thread_context_guard ctx(this);
598	834x	lock_type lock(mutex_);
599
600	834x	std::size_t n = 0;
601		for (;;)
602		{
603	364467x	if (!do_one(lock, -1, &ctx.frame_))
604	834x	break;
605	363633x	if (n != (std::numeric_limits<std::size_t>::max)())
606	363633x	++n;
607	363633x	if (!lock.owns_lock())
608	270172x	lock.lock();
609		}
610	834x	return n;
611	834x	}
612
613		inline std::size_t
614	22x	reactor_scheduler::run_one()
615		{
616	44x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
617		{
618	✗	stop();
619	✗	return 0;
620		}
621
622	22x	reactor_thread_context_guard ctx(this);
623	22x	lock_type lock(mutex_);
624	22x	return do_one(lock, -1, &ctx.frame_);
625	22x	}
626
627		inline std::size_t
628	62x	reactor_scheduler::wait_one(long usec)
629		{
630	124x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
631		{
632	20x	stop();
633	20x	return 0;
634		}
635
636	42x	reactor_thread_context_guard ctx(this);
637	42x	lock_type lock(mutex_);
638	42x	return do_one(lock, usec, &ctx.frame_);
639	42x	}
640
641		inline std::size_t
642	18x	reactor_scheduler::poll()
643		{
644	36x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
645		{
646	2x	stop();
647	2x	return 0;
648		}
649
650	16x	reactor_thread_context_guard ctx(this);
651	16x	lock_type lock(mutex_);
652
653	16x	std::size_t n = 0;
654		for (;;)
655		{
656	50x	if (!do_one(lock, 0, &ctx.frame_))
657	16x	break;
658	34x	if (n != (std::numeric_limits<std::size_t>::max)())
659	34x	++n;
660	34x	if (!lock.owns_lock())
661	34x	lock.lock();
662		}
663	16x	return n;
664	16x	}
665
666		inline std::size_t
667	8x	reactor_scheduler::poll_one()
668		{
669	16x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
670		{
671	4x	stop();
672	4x	return 0;
673		}
674
675	4x	reactor_thread_context_guard ctx(this);
676	4x	lock_type lock(mutex_);
677	4x	return do_one(lock, 0, &ctx.frame_);
678	4x	}
679
680		inline void
681	29616x	reactor_scheduler::work_started() noexcept
682		{
683	29616x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
684	29616x	}
685
686		inline void
687	46464x	reactor_scheduler::work_finished() noexcept
688		{
689	92928x	if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
690	822x	stop();
691	46464x	}
692
693		inline void
694	239705x	reactor_scheduler::compensating_work_started() const noexcept
695		{
696	239705x	auto* ctx = reactor_find_context(this);
697	239705x	if (ctx)
698	239705x	++ctx->private_outstanding_work;
699	239705x	}
700
701		inline void
702	✗	reactor_scheduler::drain_thread_queue(
703		ready_queue& queue, std::int64_t count) const
704		{
705	✗	if (count > 0)
706	✗	outstanding_work_.fetch_add(count, std::memory_order_relaxed);
707
708	✗	lock_type lock(mutex_);
709	✗	completed_ops_.splice(queue);
710	✗	if (count > 0)
711	✗	maybe_unlock_and_signal_one(lock);
712	✗	}
713
714		inline void
715	13991x	reactor_scheduler::post_deferred_completions(ready_queue& ops) const
716		{
717	13991x	if (ops.empty())
718	13991x	return;
719
720	✗	if (auto* ctx = reactor_find_context(this))
721		{
722	✗	ctx->private_queue.splice(ops);
723	✗	return;
724		}
725
726	✗	lock_type lock(mutex_);
727	✗	completed_ops_.splice(ops);
728	✗	wake_one_thread_and_unlock(lock);
729	✗	}
730
731		inline void
732	1219x	reactor_scheduler::shutdown_drain()
733		{
734	1219x	lock_type lock(mutex_);
735
736	2621x	while (auto e = completed_ops_.pop())
737		{
738	1402x	if (ready_is_continuation(e))
739		{
740	4x	lock.unlock();
741	4x	if (auto h = ready_as_cont(e)->h)
742	4x	h.destroy();
743	4x	lock.lock();
744		}
745		else
746		{
747	1398x	auto* op = ready_as_op(e);
748	1398x	if (op == &task_op_)
749	1219x	continue;
750	179x	lock.unlock();
751	179x	op->destroy();
752	179x	lock.lock();
753		}
754	1402x	}
755
756	1219x	signal_all(lock);
757	1219x	}
758
759		inline void
760	2065x	reactor_scheduler::signal_all(lock_type&) const
761		{
762	2065x	state_ \|= signaled_bit;
763	2065x	cond_.notify_all();
764	2065x	}
765
766		inline bool
767	9486x	reactor_scheduler::maybe_unlock_and_signal_one(
768		lock_type& lock) const
769		{
770	9486x	state_ \|= signaled_bit;
771	9486x	if (state_ > signaled_bit)
772		{
773	✗	lock.unlock();
774	✗	cond_.notify_one();
775	✗	return true;
776		}
777	9486x	return false;
778		}
779
780		inline bool
781	409575x	reactor_scheduler::unlock_and_signal_one(
782		lock_type& lock) const
783		{
784	409575x	state_ \|= signaled_bit;
785	409575x	bool have_waiters = state_ > signaled_bit;
786	409575x	lock.unlock();
787	409575x	if (have_waiters)
788	6x	cond_.notify_one();
789	409575x	return have_waiters;
790		}
791
792		inline void
793	8x	reactor_scheduler::clear_signal() const
794		{
795	8x	state_ &= ~signaled_bit;
796	8x	}
797
798		inline void
799	8x	reactor_scheduler::wait_for_signal(
800		lock_type& lock) const
801		{
802	17x	while ((state_ & signaled_bit) == 0)
803		{
804	9x	state_ += waiter_increment;
805	9x	cond_.wait(lock);
806	9x	state_ -= waiter_increment;
807		}
808	8x	}
809
810		inline void
811	✗	reactor_scheduler::wait_for_signal_for(
812		lock_type& lock, long timeout_us) const
813		{
814	✗	if ((state_ & signaled_bit) == 0)
815		{
816	✗	state_ += waiter_increment;
817	✗	cond_.wait_for(lock, std::chrono::microseconds(timeout_us));
818	✗	state_ -= waiter_increment;
819		}
820	✗	}
821
822		inline void
823	9486x	reactor_scheduler::wake_one_thread_and_unlock(
824		lock_type& lock) const
825		{
826	9486x	if (maybe_unlock_and_signal_one(lock))
827	✗	return;
828
829	9486x	if (task_running_.load(std::memory_order_relaxed) && !task_interrupted_)
830		{
831	108x	task_interrupted_ = true;
832	108x	lock.unlock();
833	108x	interrupt_reactor();
834		}
835		else
836		{
837	9378x	lock.unlock();
838		}
839		}
840
841	363717x	inline reactor_scheduler::work_cleanup::~work_cleanup()
842		{
843	363717x	if (ctx)
844		{
845	363717x	std::int64_t produced = ctx->private_outstanding_work;
846	363717x	if (produced > 1)
847	306x	sched->outstanding_work_.fetch_add(
848		produced - 1, std::memory_order_relaxed);
849	363411x	else if (produced < 1)
850	30851x	sched->work_finished();
851	363717x	ctx->private_outstanding_work = 0;
852
853	363717x	if (!ctx->private_queue.empty())
854		{
855	93461x	lock->lock();
856	93461x	sched->completed_ops_.splice(ctx->private_queue);
857		}
858		}
859		else
860		{
861	✗	sched->work_finished();
862		}
863	363717x	}
864
865	538476x	inline reactor_scheduler::task_cleanup::~task_cleanup()
866		{
867	269238x	if (!ctx)
868	✗	return;
869
870	269238x	if (ctx->private_outstanding_work > 0)
871		{
872	7090x	sched->outstanding_work_.fetch_add(
873	7090x	ctx->private_outstanding_work, std::memory_order_relaxed);
874	7090x	ctx->private_outstanding_work = 0;
875		}
876
877	269238x	if (!ctx->private_queue.empty())
878		{
879	7090x	if (!lock->owns_lock())
880	✗	lock->lock();
881	7090x	sched->completed_ops_.splice(ctx->private_queue);
882		}
883	269238x	}
884
885		inline std::size_t
886	364585x	reactor_scheduler::do_one(
887		lock_type& lock, long timeout_us, context_type* ctx)
888		{
889		for (;;)
890		{
891	633813x	if (stopped_.load(std::memory_order_acquire))
892	835x	return 0;
893
894	632978x	std::uintptr_t e = completed_ops_.pop();
895	632978x	scheduler_op* op = ready_is_continuation(e) ? nullptr : ready_as_op(e);
896
897		// Handle reactor sentinel — time to poll for I/O
898	632978x	if (op == &task_op_)
899		{
900		bool more_handlers =
901	269251x	!completed_ops_.empty() \|\| (ctx && !ctx->private_queue.empty());
902
903	492616x	if (!more_handlers &&
904	446730x	(outstanding_work_.load(std::memory_order_acquire) == 0 \|\|
905		timeout_us == 0))
906		{
907	13x	completed_ops_.push(&task_op_);
908	13x	return 0;
909		}
910
911	269238x	long task_timeout_us = more_handlers ? 0 : timeout_us;
912	269238x	task_interrupted_ = task_timeout_us == 0;
913	269238x	task_running_.store(true, std::memory_order_release);
914
915		// Wake a peer to take the pending handlers while this thread
916		// polls the reactor; skipped when one_thread_ (no peer exists).
917	269238x	if (more_handlers && !one_thread_)
918	45879x	unlock_and_signal_one(lock);
919
920		try
921		{
922	269238x	run_task(lock, ctx, task_timeout_us);
923		}
924	✗	catch (...)
925		{
926	✗	task_running_.store(false, std::memory_order_relaxed);
927	✗	throw;
928	✗	}
929
930	269238x	task_running_.store(false, std::memory_order_relaxed);
931	269238x	completed_ops_.push(&task_op_);
932	269238x	if (timeout_us > 0)
933	18x	return 0;
934	269220x	continue;
935	269220x	}
936
937		// Handle ready entry (op or continuation)
938	363727x	if (e != 0)
939		{
940	363717x	bool more = !completed_ops_.empty();
941
942	363717x	if (more && !one_thread_)
943		{
944		// Wake a peer for the remaining work; unassisted if none
945		// was parked to take it.
946	363696x	ctx->unassisted = !unlock_and_signal_one(lock);
947		}
948		else
949		{
950		// No peer to wake (one_thread_, or nothing more queued).
951	21x	ctx->unassisted = more;
952	21x	lock.unlock();
953		}
954
955	363717x	work_cleanup on_exit{this, &lock, ctx};
956		(void)on_exit;
957
958	363717x	if (ready_is_continuation(e))
959	15090x	ready_as_cont(e)->h.resume();
960		else
961	348627x	(*op)();
962	363717x	return 1;
963	363717x	}
964
965		// Try private queue before blocking
966	10x	if (reactor_drain_private_queue(ctx, outstanding_work_, completed_ops_))
967	✗	continue;
968
969	20x	if (outstanding_work_.load(std::memory_order_acquire) == 0 \|\|
970		timeout_us == 0)
971	2x	return 0;
972
973	8x	clear_signal();
974	8x	if (timeout_us < 0)
975	8x	wait_for_signal(lock);
976		else
977	✗	wait_for_signal_for(lock, timeout_us);
978	269228x	}
979		}
980
981		} // namespace boost::corosio::detail
982
983		#endif // BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SCHEDULER_HPP
984