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

78.7% Lines (299/380) 85.7% List of functions (42/49) 56.1% Branches (120/214)

[ ] prev/next file n p prev/next uncovered line

reactor_scheduler.hpp

f(x) Functions (49)

Function Calls Lines Branches Blocks

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			#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/scheduler.hpp>
17			#include <boost/corosio/detail/scheduler_op.hpp>
18			#include <boost/corosio/detail/thread_local_ptr.hpp>
19
20			#include <atomic>
21			#include <chrono>
22			#include <coroutine>
23			#include <cstddef>
24			#include <cstdint>
25			#include <limits>
26			#include <memory>
27			#include <stdexcept>
28
29			#include <boost/corosio/detail/conditionally_enabled_mutex.hpp>
30			#include <boost/corosio/detail/conditionally_enabled_event.hpp>
31
32			namespace boost::corosio::detail {
33
34			// Forward declarations
35			class reactor_scheduler;
36			class timer_service;
37
38			/** Per-thread state for a reactor scheduler.
39
40			Each thread running a scheduler's event loop has one of these
41			on a thread-local stack. It holds a private work queue and
42			inline completion budget for speculative I/O fast paths.
43			*/
44			struct BOOST_COROSIO_SYMBOL_VISIBLE reactor_scheduler_context
45			{
46			/// Scheduler this context belongs to.
47			reactor_scheduler const* key;
48
49			/// Next context frame on this thread's stack.
50			reactor_scheduler_context* next;
51
52			/// Private work queue for reduced contention.
53			op_queue private_queue;
54
55			/// Unflushed work count for the private queue.
56			std::int64_t private_outstanding_work;
57
58			/// Remaining inline completions allowed this cycle.
59			int inline_budget;
60
61			/// Maximum inline budget (adaptive, 2-16).
62			int inline_budget_max;
63
64			/// True if no other thread absorbed queued work last cycle.
65			bool unassisted;
66
67			/// Construct a context frame linked to @a n.
68			reactor_scheduler_context(
69			reactor_scheduler const* k,
70			reactor_scheduler_context* n);
71			};
72
73			/// Thread-local context stack for reactor schedulers.
74			inline thread_local_ptr<reactor_scheduler_context> reactor_context_stack;
75
76			/// Find the context frame for a scheduler on this thread.
77			inline reactor_scheduler_context*
78		3074229x	reactor_find_context(reactor_scheduler const* self) noexcept
79			{
80	2/2 ✓ Branch 0 taken 3061829 times. ✓ Branch 1 taken 12400 times.	3074229x	for (auto* c = reactor_context_stack.get(); c != nullptr; c = c->next)
81			{
82	1/2 ✓ Branch 0 taken 3061829 times. ✗ Branch 1 not taken.	3061829x	if (c->key == self)
83		3061829x	return c;
84		✗	}
85		12400x	return nullptr;
86		3074229x	}
87
88			/// Flush private work count to global counter.
89			inline void
90		✗	reactor_flush_private_work(
91			reactor_scheduler_context* ctx,
92			std::atomic<std::int64_t>& outstanding_work) noexcept
93			{
94		✗	if (ctx && ctx->private_outstanding_work > 0)
95			{
96		✗	outstanding_work.fetch_add(
97		✗	ctx->private_outstanding_work, std::memory_order_relaxed);
98		✗	ctx->private_outstanding_work = 0;
99		✗	}
100		✗	}
101
102			/** Drain private queue to global queue, flushing work count first.
103
104			@return True if any ops were drained.
105			*/
106			inline bool
107		11x	reactor_drain_private_queue(
108			reactor_scheduler_context* ctx,
109			std::atomic<std::int64_t>& outstanding_work,
110			op_queue& completed_ops) noexcept
111			{
112	2/4 ✓ Branch 0 taken 11 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 11 times. ✗ Branch 3 not taken.	11x	if (!ctx \|\| ctx->private_queue.empty())
113		11x	return false;
114
115		✗	reactor_flush_private_work(ctx, outstanding_work);
116		✗	completed_ops.splice(ctx->private_queue);
117		✗	return true;
118		11x	}
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
141			: public scheduler
142			, public capy::execution_context::service
143			{
144			public:
145			using key_type = scheduler;
146			using context_type = reactor_scheduler_context;
147			using mutex_type = conditionally_enabled_mutex;
148			using lock_type = mutex_type::scoped_lock;
149			using event_type = conditionally_enabled_event;
150
151			/// Post a coroutine for deferred execution.
152			void post(std::coroutine_handle<> h) const override;
153
154			/// Post a scheduler operation for deferred execution.
155			void post(scheduler_op* h) const override;
156
157			/// Return true if called from a thread running this scheduler.
158			bool running_in_this_thread() const noexcept override;
159
160			/// Request the scheduler to stop dispatching handlers.
161			void stop() override;
162
163			/// Return true if the scheduler has been stopped.
164			bool stopped() const noexcept override;
165
166			/// Reset the stopped state so `run()` can resume.
167			void restart() override;
168
169			/// Run the event loop until no work remains.
170			std::size_t run() override;
171
172			/// Run until one handler completes or no work remains.
173			std::size_t run_one() override;
174
175			/// Run until one handler completes or @a usec elapses.
176			std::size_t wait_one(long usec) override;
177
178			/// Run ready handlers without blocking.
179			std::size_t poll() override;
180
181			/// Run at most one ready handler without blocking.
182			std::size_t poll_one() override;
183
184			/// Increment the outstanding work count.
185			void work_started() noexcept override;
186
187			/// Decrement the outstanding work count, stopping on zero.
188			void work_finished() noexcept override;
189
190			/** Reset the thread's inline completion budget.
191
192			Called at the start of each posted completion handler to
193			grant a fresh budget for speculative inline completions.
194			*/
195			void reset_inline_budget() const noexcept;
196
197			/** Consume one unit of inline budget if available.
198
199			@return True if budget was available and consumed.
200			*/
201			bool try_consume_inline_budget() const noexcept;
202
203			/** Offset a forthcoming work_finished from work_cleanup.
204
205			Called by descriptor_state when all I/O returned EAGAIN and
206			no handler will be executed. Must be called from a scheduler
207			thread.
208			*/
209			void compensating_work_started() const noexcept;
210
211			/** Drain work from thread context's private queue to global queue.
212
213			Flushes private work count to the global counter, then
214			transfers the queue under mutex protection.
215
216			@param queue The private queue to drain.
217			@param count Private work count to flush before draining.
218			*/
219			void drain_thread_queue(op_queue& queue, std::int64_t count) const;
220
221			/** Post completed operations for deferred invocation.
222
223			If called from a thread running this scheduler, operations
224			go to the thread's private queue (fast path). Otherwise,
225			operations are added to the global queue under mutex and a
226			waiter is signaled.
227
228			@par Preconditions
229			work_started() must have been called for each operation.
230
231			@param ops Queue of operations to post.
232			*/
233			void post_deferred_completions(op_queue& ops) const;
234
235			/** Apply runtime configuration to the scheduler.
236
237			Called by `io_context` after construction. Values that do
238			not apply to this backend are silently ignored.
239
240			@param max_events Event buffer size for epoll/kqueue.
241			@param budget_init Starting inline completion budget.
242			@param budget_max Hard ceiling on adaptive budget ramp-up.
243			@param unassisted Budget when single-threaded.
244			*/
245			virtual void configure_reactor(
246			unsigned max_events,
247			unsigned budget_init,
248			unsigned budget_max,
249			unsigned unassisted);
250
251			/// Return the configured initial inline budget.
252		2720x	unsigned inline_budget_initial() const noexcept
253			{
254		2720x	return inline_budget_initial_;
255			}
256
257			/// Return true if single-threaded (lockless) mode is active.
258		66x	bool is_single_threaded() const noexcept
259			{
260		66x	return single_threaded_;
261			}
262
263			/** Enable or disable single-threaded (lockless) mode.
264
265			When enabled, all scheduler mutex and condition variable
266			operations become no-ops. Cross-thread post() is
267			undefined behavior.
268			*/
269		✗	void configure_single_threaded(bool v) noexcept
270			{
271		✗	single_threaded_ = v;
272		✗	mutex_.set_enabled(!v);
273		✗	cond_.set_enabled(!v);
274		✗	}
275
276			protected:
277		679x	timer_service* timer_svc_ = nullptr;
278		679x	bool single_threaded_ = false;
279
280		2037x	reactor_scheduler() = default;
281
282			/** Drain completed_ops during shutdown.
283
284			Pops all operations from the global queue and destroys them,
285			skipping the task sentinel. Signals all waiting threads.
286			Derived classes call this from their shutdown() override
287			before performing platform-specific cleanup.
288			*/
289			void shutdown_drain();
290
291			/// RAII guard that re-inserts the task sentinel after `run_task`.
292			struct task_cleanup
293			{
294			reactor_scheduler const* sched;
295			lock_type* lock;
296			context_type* ctx;
297			~task_cleanup();
298			};
299
300		679x	mutable mutex_type mutex_{true};
301		679x	mutable event_type cond_{true};
302			mutable op_queue completed_ops_;
303		679x	mutable std::atomic<std::int64_t> outstanding_work_{0};
304		679x	std::atomic<bool> stopped_{false};
305		679x	mutable std::atomic<bool> task_running_{false};
306		679x	mutable bool task_interrupted_ = false;
307
308			// Runtime-configurable reactor tuning parameters.
309			// Defaults match the library's built-in values.
310		679x	unsigned max_events_per_poll_ = 128;
311		679x	unsigned inline_budget_initial_ = 2;
312		679x	unsigned inline_budget_max_ = 16;
313		679x	unsigned unassisted_budget_ = 4;
314
315			/// Bit 0 of `state_`: set when the condvar should be signaled.
316			static constexpr std::size_t signaled_bit = 1;
317
318			/// Increment per waiting thread in `state_`.
319			static constexpr std::size_t waiter_increment = 2;
320		679x	mutable std::size_t state_ = 0;
321
322			/// Sentinel op that triggers a reactor poll when dequeued.
323			struct task_op final : scheduler_op
324			{
325		✗	void operator()() override {}
326		✗	void destroy() override {}
327			};
328			task_op task_op_;
329
330			/// Run the platform-specific reactor poll.
331			virtual void
332			run_task(lock_type& lock, context_type* ctx,
333			long timeout_us) = 0;
334
335			/// Wake a blocked reactor (e.g. write to eventfd or pipe).
336			virtual void interrupt_reactor() const = 0;
337
338			private:
339			struct work_cleanup
340			{
341			reactor_scheduler* sched;
342			lock_type* lock;
343			context_type* ctx;
344			~work_cleanup();
345			};
346
347			std::size_t do_one(
348			lock_type& lock, long timeout_us, context_type* ctx);
349
350			void signal_all(lock_type& lock) const;
351			bool maybe_unlock_and_signal_one(lock_type& lock) const;
352			bool unlock_and_signal_one(lock_type& lock) const;
353			void clear_signal() const;
354			void wait_for_signal(lock_type& lock) const;
355			void wait_for_signal_for(
356			lock_type& lock, long timeout_us) const;
357			void wake_one_thread_and_unlock(lock_type& lock) const;
358			};
359
360			/** RAII guard that pushes/pops a scheduler context frame.
361
362			On construction, pushes a new context frame onto the
363			thread-local stack. On destruction, drains any remaining
364			private queue items to the global queue and pops the frame.
365			*/
366			struct reactor_thread_context_guard
367			{
368			/// The context frame managed by this guard.
369			reactor_scheduler_context frame_;
370
371			/// Construct the guard, pushing a frame for @a sched.
372		5440x	explicit reactor_thread_context_guard(
373			reactor_scheduler const* sched) noexcept
374	1/2 ✓ Branch 0 taken 2720 times. ✗ Branch 1 not taken.	2720x	: frame_(sched, reactor_context_stack.get())
375		2720x	{
376		2720x	reactor_context_stack.set(&frame_);
377		5440x	}
378
379			/// Destroy the guard, draining private work and popping the frame.
380		5440x	~reactor_thread_context_guard() noexcept
381		2720x	{
382	1/2 ✓ Branch 0 taken 2720 times. ✗ Branch 1 not taken.	2720x	if (!frame_.private_queue.empty())
383		✗	frame_.key->drain_thread_queue(
384		✗	frame_.private_queue, frame_.private_outstanding_work);
385		2720x	reactor_context_stack.set(frame_.next);
386		5440x	}
387			};
388
389			// ---- Inline implementations ------------------------------------------------
390
391			inline
392		8160x	reactor_scheduler_context::reactor_scheduler_context(
393			reactor_scheduler const* k,
394			reactor_scheduler_context* n)
395		2720x	: key(k)
396		2720x	, next(n)
397		2720x	, private_outstanding_work(0)
398		2720x	, inline_budget(0)
399		5440x	, inline_budget_max(
400		2720x	static_cast<int>(k->inline_budget_initial()))
401		2720x	, unassisted(false)
402		2720x	{
403		5440x	}
404
405			inline void
406		✗	reactor_scheduler::configure_reactor(
407			unsigned max_events,
408			unsigned budget_init,
409			unsigned budget_max,
410			unsigned unassisted)
411			{
412		✗	if (max_events < 1 \|\|
413		✗	max_events > static_cast<unsigned>(std::numeric_limits<int>::max()))
414		✗	throw std::out_of_range(
415			"max_events_per_poll must be in [1, INT_MAX]");
416		✗	if (budget_max < 1 \|\|
417		✗	budget_max > static_cast<unsigned>(std::numeric_limits<int>::max()))
418		✗	throw std::out_of_range(
419			"inline_budget_max must be in [1, INT_MAX]");
420
421			// Clamp initial and unassisted to budget_max.
422		✗	if (budget_init > budget_max)
423		✗	budget_init = budget_max;
424		✗	if (unassisted > budget_max)
425		✗	unassisted = budget_max;
426
427		✗	max_events_per_poll_ = max_events;
428		✗	inline_budget_initial_ = budget_init;
429		✗	inline_budget_max_ = budget_max;
430		✗	unassisted_budget_ = unassisted;
431		✗	}
432
433			inline void
434		431910x	reactor_scheduler::reset_inline_budget() const noexcept
435			{
436	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 431910 times.	431910x	if (auto* ctx = reactor_find_context(this))
437			{
438			// Cap when no other thread absorbed queued work
439	1/2 ✓ Branch 0 taken 431910 times. ✗ Branch 1 not taken.	431910x	if (ctx->unassisted)
440			{
441		431910x	ctx->inline_budget_max =
442		431910x	static_cast<int>(unassisted_budget_);
443		431910x	ctx->inline_budget =
444		431910x	static_cast<int>(unassisted_budget_);
445		431910x	return;
446			}
447			// Ramp up when previous cycle fully consumed budget
448		✗	if (ctx->inline_budget == 0)
449		✗	ctx->inline_budget_max = (std::min)(
450		✗	ctx->inline_budget_max * 2,
451		✗	static_cast<int>(inline_budget_max_));
452		✗	else if (ctx->inline_budget < ctx->inline_budget_max)
453		✗	ctx->inline_budget_max =
454		✗	static_cast<int>(inline_budget_initial_);
455		✗	ctx->inline_budget = ctx->inline_budget_max;
456		✗	}
457		431910x	}
458
459			inline bool
460		1648888x	reactor_scheduler::try_consume_inline_budget() const noexcept
461			{
462	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 1648888 times.	1648888x	if (auto* ctx = reactor_find_context(this))
463			{
464	2/2 ✓ Branch 0 taken 1342515 times. ✓ Branch 1 taken 306373 times.	1648888x	if (ctx->inline_budget > 0)
465			{
466		1342515x	--ctx->inline_budget;
467		1342515x	return true;
468			}
469		306373x	}
470		306373x	return false;
471		1648888x	}
472
473			inline void
474		6830x	reactor_scheduler::post(std::coroutine_handle<> h) const
475			{
476			struct post_handler final : scheduler_op
477			{
478			std::coroutine_handle<> h_;
479
480		13654x	explicit post_handler(std::coroutine_handle<> h) : h_(h) {}
481		13656x	~post_handler() override = default;
482
483		6819x	void operator()() override
484			{
485		6819x	auto saved = h_;
486	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 6819 times.	6819x	delete this;
487			// Ensure stores from the posting thread are visible
488		6819x	std::atomic_thread_fence(std::memory_order_acquire);
489		6819x	saved.resume();
490		6819x	}
491
492		9x	void destroy() override
493			{
494		9x	auto saved = h_;
495	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 9 times.	9x	delete this;
496		9x	saved.destroy();
497		9x	}
498			};
499
500		6830x	auto ph = std::make_unique<post_handler>(h);
501
502	2/2 ✓ Branch 0 taken 6 times. ✓ Branch 1 taken 6824 times.	6830x	if (auto* ctx = reactor_find_context(this))
503			{
504		6x	++ctx->private_outstanding_work;
505		6x	ctx->private_queue.push(ph.release());
506		6x	return;
507			}
508
509		6824x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
510
511	1/2 ✓ Branch 0 taken 6824 times. ✗ Branch 1 not taken.	6824x	lock_type lock(mutex_);
512		6824x	completed_ops_.push(ph.release());
513	1/2 ✓ Branch 0 taken 6824 times. ✗ Branch 1 not taken.	6824x	wake_one_thread_and_unlock(lock);
514		6830x	}
515
516			inline void
517		321803x	reactor_scheduler::post(scheduler_op* h) const
518			{
519	2/2 ✓ Branch 0 taken 321629 times. ✓ Branch 1 taken 174 times.	321803x	if (auto* ctx = reactor_find_context(this))
520			{
521		321629x	++ctx->private_outstanding_work;
522		321629x	ctx->private_queue.push(h);
523		321629x	return;
524			}
525
526		174x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
527
528		174x	lock_type lock(mutex_);
529		174x	completed_ops_.push(h);
530	1/2 ✓ Branch 0 taken 174 times. ✗ Branch 1 not taken.	174x	wake_one_thread_and_unlock(lock);
531		321803x	}
532
533			inline bool
534		5815x	reactor_scheduler::running_in_this_thread() const noexcept
535			{
536		5815x	return reactor_find_context(this) != nullptr;
537			}
538
539			inline void
540		2625x	reactor_scheduler::stop()
541			{
542		2625x	lock_type lock(mutex_);
543	2/2 ✓ Branch 0 taken 15 times. ✓ Branch 1 taken 2610 times.	2625x	if (!stopped_.load(std::memory_order_acquire))
544			{
545		2610x	stopped_.store(true, std::memory_order_release);
546	1/2 ✓ Branch 0 taken 2610 times. ✗ Branch 1 not taken.	2610x	signal_all(lock);
547	1/2 ✓ Branch 0 taken 2610 times. ✗ Branch 1 not taken.	2610x	interrupt_reactor();
548		2610x	}
549		2625x	}
550
551			inline bool
552		72x	reactor_scheduler::stopped() const noexcept
553			{
554		72x	return stopped_.load(std::memory_order_acquire);
555			}
556
557			inline void
558		2241x	reactor_scheduler::restart()
559			{
560		2241x	stopped_.store(false, std::memory_order_release);
561		2241x	}
562
563			inline std::size_t
564		2616x	reactor_scheduler::run()
565			{
566	2/2 ✓ Branch 0 taken 2613 times. ✓ Branch 1 taken 3 times.	2616x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
567			{
568		3x	stop();
569		3x	return 0;
570			}
571
572		2613x	reactor_thread_context_guard ctx(this);
573	1/2 ✓ Branch 0 taken 2613 times. ✗ Branch 1 not taken.	2613x	lock_type lock(mutex_);
574
575		2613x	std::size_t n = 0;
576		1114876x	for (;;)
577			{
578	3/4 ✓ Branch 0 taken 1114876 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 1112263 times. ✓ Branch 3 taken 2613 times.	1114876x	if (!do_one(lock, -1, &ctx.frame_))
579		2613x	break;
580	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 1112263 times.	1112263x	if (n != (std::numeric_limits<std::size_t>::max)())
581		1112263x	++n;
582	2/2 ✓ Branch 0 taken 797199 times. ✓ Branch 1 taken 315064 times.	1112263x	if (!lock.owns_lock())
583	1/2 ✓ Branch 0 taken 797199 times. ✗ Branch 1 not taken.	797199x	lock.lock();
584			}
585		2613x	return n;
586		2616x	}
587
588			inline std::size_t
589		2x	reactor_scheduler::run_one()
590			{
591	1/2 ✓ Branch 0 taken 2 times. ✗ Branch 1 not taken.	2x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
592			{
593		✗	stop();
594		✗	return 0;
595			}
596
597		2x	reactor_thread_context_guard ctx(this);
598	1/2 ✓ Branch 0 taken 2 times. ✗ Branch 1 not taken.	2x	lock_type lock(mutex_);
599	1/2 ✓ Branch 0 taken 2 times. ✗ Branch 1 not taken.	2x	return do_one(lock, -1, &ctx.frame_);
600		2x	}
601
602			inline std::size_t
603		108x	reactor_scheduler::wait_one(long usec)
604			{
605	2/2 ✓ Branch 0 taken 96 times. ✓ Branch 1 taken 12 times.	108x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
606			{
607		12x	stop();
608		12x	return 0;
609			}
610
611		96x	reactor_thread_context_guard ctx(this);
612	1/2 ✓ Branch 0 taken 96 times. ✗ Branch 1 not taken.	96x	lock_type lock(mutex_);
613	1/2 ✓ Branch 0 taken 96 times. ✗ Branch 1 not taken.	96x	return do_one(lock, usec, &ctx.frame_);
614		108x	}
615
616			inline std::size_t
617		8x	reactor_scheduler::poll()
618			{
619	2/2 ✓ Branch 0 taken 7 times. ✓ Branch 1 taken 1 time.	8x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
620			{
621		1x	stop();
622		1x	return 0;
623			}
624
625		7x	reactor_thread_context_guard ctx(this);
626	1/2 ✓ Branch 0 taken 7 times. ✗ Branch 1 not taken.	7x	lock_type lock(mutex_);
627
628		7x	std::size_t n = 0;
629		15x	for (;;)
630			{
631	3/4 ✓ Branch 0 taken 15 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 8 times. ✓ Branch 3 taken 7 times.	15x	if (!do_one(lock, 0, &ctx.frame_))
632		7x	break;
633	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 8 times.	8x	if (n != (std::numeric_limits<std::size_t>::max)())
634		8x	++n;
635	1/2 ✓ Branch 0 taken 8 times. ✗ Branch 1 not taken.	8x	if (!lock.owns_lock())
636	1/2 ✓ Branch 0 taken 8 times. ✗ Branch 1 not taken.	8x	lock.lock();
637			}
638		7x	return n;
639		8x	}
640
641			inline std::size_t
642		4x	reactor_scheduler::poll_one()
643			{
644	2/2 ✓ Branch 0 taken 2 times. ✓ Branch 1 taken 2 times.	4x	if (outstanding_work_.load(std::memory_order_acquire) == 0)
645			{
646		2x	stop();
647		2x	return 0;
648			}
649
650		2x	reactor_thread_context_guard ctx(this);
651	1/2 ✓ Branch 0 taken 2 times. ✗ Branch 1 not taken.	2x	lock_type lock(mutex_);
652	1/2 ✓ Branch 0 taken 2 times. ✗ Branch 1 not taken.	2x	return do_one(lock, 0, &ctx.frame_);
653		4x	}
654
655			inline void
656		138708x	reactor_scheduler::work_started() noexcept
657			{
658		138708x	outstanding_work_.fetch_add(1, std::memory_order_relaxed);
659		138708x	}
660
661			inline void
662		152229x	reactor_scheduler::work_finished() noexcept
663			{
664	2/2 ✓ Branch 0 taken 149629 times. ✓ Branch 1 taken 2600 times.	152229x	if (outstanding_work_.fetch_sub(1, std::memory_order_acq_rel) == 1)
665	1/2 ✓ Branch 0 taken 2600 times. ✗ Branch 1 not taken.	2600x	stop();
666		152229x	}
667
668			inline void
669		658984x	reactor_scheduler::compensating_work_started() const noexcept
670			{
671		658984x	auto* ctx = reactor_find_context(this);
672	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 658984 times.	658984x	if (ctx)
673		658984x	++ctx->private_outstanding_work;
674		658984x	}
675
676			inline void
677		✗	reactor_scheduler::drain_thread_queue(
678			op_queue& queue, std::int64_t count) const
679			{
680		✗	if (count > 0)
681		✗	outstanding_work_.fetch_add(count, std::memory_order_relaxed);
682
683		✗	lock_type lock(mutex_);
684		✗	completed_ops_.splice(queue);
685		✗	if (count > 0)
686		✗	maybe_unlock_and_signal_one(lock);
687		✗	}
688
689			inline void
690		124727x	reactor_scheduler::post_deferred_completions(op_queue& ops) const
691			{
692	1/2 ✓ Branch 0 taken 124727 times. ✗ Branch 1 not taken.	124727x	if (ops.empty())
693		124727x	return;
694
695		✗	if (auto* ctx = reactor_find_context(this))
696			{
697		✗	ctx->private_queue.splice(ops);
698		✗	return;
699			}
700
701		✗	lock_type lock(mutex_);
702		✗	completed_ops_.splice(ops);
703		✗	wake_one_thread_and_unlock(lock);
704		124727x	}
705
706			inline void
707		679x	reactor_scheduler::shutdown_drain()
708			{
709		679x	lock_type lock(mutex_);
710
711	2/2 ✓ Branch 0 taken 679 times. ✓ Branch 1 taken 781 times.	1460x	while (auto* h = completed_ops_.pop())
712			{
713	2/2 ✓ Branch 0 taken 102 times. ✓ Branch 1 taken 679 times.	781x	if (h == &task_op_)
714		679x	continue;
715	1/2 ✓ Branch 0 taken 102 times. ✗ Branch 1 not taken.	102x	lock.unlock();
716	1/2 ✓ Branch 0 taken 102 times. ✗ Branch 1 not taken.	102x	h->destroy();
717	1/2 ✓ Branch 0 taken 102 times. ✗ Branch 1 not taken.	102x	lock.lock();
718			}
719
720	1/2 ✓ Branch 0 taken 679 times. ✗ Branch 1 not taken.	679x	signal_all(lock);
721		679x	}
722
723			inline void
724		3289x	reactor_scheduler::signal_all(lock_type&) const
725			{
726		3289x	state_ \|= signaled_bit;
727		3289x	cond_.notify_all();
728		3289x	}
729
730			inline bool
731		6999x	reactor_scheduler::maybe_unlock_and_signal_one(
732			lock_type& lock) const
733			{
734		6999x	state_ \|= signaled_bit;
735	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 6999 times.	6999x	if (state_ > signaled_bit)
736			{
737		✗	lock.unlock();
738		✗	cond_.notify_one();
739		✗	return true;
740			}
741		6999x	return false;
742		6999x	}
743
744			inline bool
745		1173869x	reactor_scheduler::unlock_and_signal_one(
746			lock_type& lock) const
747			{
748		1173869x	state_ \|= signaled_bit;
749		1173869x	bool have_waiters = state_ > signaled_bit;
750		1173869x	lock.unlock();
751	1/2 ✓ Branch 0 taken 1173869 times. ✗ Branch 1 not taken.	1173869x	if (have_waiters)
752		✗	cond_.notify_one();
753		1173869x	return have_waiters;
754			}
755
756			inline void
757		3x	reactor_scheduler::clear_signal() const
758			{
759		3x	state_ &= ~signaled_bit;
760		3x	}
761
762			inline void
763		3x	reactor_scheduler::wait_for_signal(
764			lock_type& lock) const
765			{
766	2/2 ✓ Branch 0 taken 3 times. ✓ Branch 1 taken 3 times.	6x	while ((state_ & signaled_bit) == 0)
767			{
768		3x	state_ += waiter_increment;
769		3x	cond_.wait(lock);
770		3x	state_ -= waiter_increment;
771			}
772		3x	}
773
774			inline void
775		✗	reactor_scheduler::wait_for_signal_for(
776			lock_type& lock, long timeout_us) const
777			{
778		✗	if ((state_ & signaled_bit) == 0)
779			{
780		✗	state_ += waiter_increment;
781		✗	cond_.wait_for(lock, std::chrono::microseconds(timeout_us));
782		✗	state_ -= waiter_increment;
783		✗	}
784		✗	}
785
786			inline void
787		6999x	reactor_scheduler::wake_one_thread_and_unlock(
788			lock_type& lock) const
789			{
790	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 6999 times.	6999x	if (maybe_unlock_and_signal_one(lock))
791		✗	return;
792
793	4/4 ✓ Branch 0 taken 96 times. ✓ Branch 1 taken 6903 times. ✓ Branch 2 taken 37 times. ✓ Branch 3 taken 59 times.	6999x	if (task_running_.load(std::memory_order_relaxed) && !task_interrupted_)
794			{
795		59x	task_interrupted_ = true;
796		59x	lock.unlock();
797		59x	interrupt_reactor();
798		59x	}
799			else
800			{
801		6940x	lock.unlock();
802			}
803		6999x	}
804
805		2224647x	inline reactor_scheduler::work_cleanup::~work_cleanup()
806		1112319x	{
807	1/2 ✓ Branch 0 taken 1112328 times. ✗ Branch 1 not taken.	1112328x	if (ctx)
808			{
809		1112328x	std::int64_t produced = ctx->private_outstanding_work;
810	2/2 ✓ Branch 0 taken 16 times. ✓ Branch 1 taken 1112312 times.	1112328x	if (produced > 1)
811		32x	sched->outstanding_work_.fetch_add(
812		16x	produced - 1, std::memory_order_relaxed);
813	2/2 ✓ Branch 0 taken 974063 times. ✓ Branch 1 taken 138249 times.	1112312x	else if (produced < 1)
814		138249x	sched->work_finished();
815		1112328x	ctx->private_outstanding_work = 0;
816
817	2/2 ✓ Branch 0 taken 797242 times. ✓ Branch 1 taken 315086 times.	1112328x	if (!ctx->private_queue.empty())
818			{
819	1/2 ✓ Branch 0 taken 315086 times. ✗ Branch 1 not taken.	315086x	lock->lock();
820		315086x	sched->completed_ops_.splice(ctx->private_queue);
821		315086x	}
822		1112328x	}
823			else
824			{
825		✗	sched->work_finished();
826			}
827		2224647x	}
828
829		1382248x	inline reactor_scheduler::task_cleanup::~task_cleanup()
830		691124x	{
831	1/2 ✓ Branch 0 taken 691124 times. ✗ Branch 1 not taken.	691124x	if (!ctx)
832		✗	return;
833
834	2/2 ✓ Branch 0 taken 684604 times. ✓ Branch 1 taken 6520 times.	691124x	if (ctx->private_outstanding_work > 0)
835			{
836		13040x	sched->outstanding_work_.fetch_add(
837		6520x	ctx->private_outstanding_work, std::memory_order_relaxed);
838		6520x	ctx->private_outstanding_work = 0;
839		6520x	}
840
841	2/2 ✓ Branch 0 taken 684604 times. ✓ Branch 1 taken 6520 times.	691124x	if (!ctx->private_queue.empty())
842			{
843	1/2 ✓ Branch 0 taken 6520 times. ✗ Branch 1 not taken.	6520x	if (!lock->owns_lock())
844		✗	lock->lock();
845		6520x	sched->completed_ops_.splice(ctx->private_queue);
846		6520x	}
847		1382248x	}
848
849			inline std::size_t
850		1114991x	reactor_scheduler::do_one(
851			lock_type& lock, long timeout_us, context_type* ctx)
852			{
853		1114994x	for (;;)
854			{
855	2/2 ✓ Branch 0 taken 1803467 times. ✓ Branch 1 taken 2608 times.	1806075x	if (stopped_.load(std::memory_order_acquire))
856		2608x	return 0;
857
858		1803467x	scheduler_op* op = completed_ops_.pop();
859
860			// Handle reactor sentinel — time to poll for I/O
861	2/2 ✓ Branch 0 taken 1112339 times. ✓ Branch 1 taken 691128 times.	1803467x	if (op == &task_op_)
862			{
863		691128x	bool more_handlers =
864	3/4 ✓ Branch 0 taken 61545 times. ✓ Branch 1 taken 629583 times. ✗ Branch 2 not taken. ✓ Branch 3 taken 629583 times.	691128x	!completed_ops_.empty() \|\| (ctx && !ctx->private_queue.empty());
865
866	4/4 ✓ Branch 0 taken 629583 times. ✓ Branch 1 taken 61545 times. ✓ Branch 2 taken 629579 times. ✓ Branch 3 taken 4 times.	1320711x	if (!more_handlers &&
867	1/2 ✓ Branch 0 taken 629583 times. ✗ Branch 1 not taken.	629583x	(outstanding_work_.load(std::memory_order_acquire) == 0 \|\|
868		629583x	timeout_us == 0))
869			{
870		4x	completed_ops_.push(&task_op_);
871		4x	return 0;
872			}
873
874	2/2 ✓ Branch 0 taken 61545 times. ✓ Branch 1 taken 629579 times.	691124x	long task_timeout_us = more_handlers ? 0 : timeout_us;
875		691124x	task_interrupted_ = task_timeout_us == 0;
876		691124x	task_running_.store(true, std::memory_order_release);
877
878	2/2 ✓ Branch 0 taken 629579 times. ✓ Branch 1 taken 61545 times.	691124x	if (more_handlers)
879		61545x	unlock_and_signal_one(lock);
880
881			try
882			{
883	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 691124 times.	691124x	run_task(lock, ctx, task_timeout_us);
884		691124x	}
885			catch (...)
886			{
887		✗	task_running_.store(false, std::memory_order_relaxed);
888		✗	throw;
889		✗	}
890
891		691124x	task_running_.store(false, std::memory_order_relaxed);
892		691124x	completed_ops_.push(&task_op_);
893	2/2 ✓ Branch 0 taken 43 times. ✓ Branch 1 taken 691081 times.	691124x	if (timeout_us > 0)
894		43x	return 0;
895		691081x	continue;
896			}
897
898			// Handle operation
899	2/2 ✓ Branch 0 taken 11 times. ✓ Branch 1 taken 1112328 times.	1112339x	if (op != nullptr)
900			{
901		1112328x	bool more = !completed_ops_.empty();
902
903	2/2 ✓ Branch 0 taken 1112324 times. ✓ Branch 1 taken 4 times.	1112328x	if (more)
904		1112324x	ctx->unassisted = !unlock_and_signal_one(lock);
905			else
906			{
907		4x	ctx->unassisted = false;
908		4x	lock.unlock();
909			}
910
911		1112328x	work_cleanup on_exit{this, &lock, ctx};
912			(void)on_exit;
913
914	1/2 ✓ Branch 0 taken 1112328 times. ✗ Branch 1 not taken.	1112328x	(*op)();
915		1112328x	return 1;
916		1112328x	}
917
918			// Try private queue before blocking
919	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 11 times.	11x	if (reactor_drain_private_queue(ctx, outstanding_work_, completed_ops_))
920		✗	continue;
921
922	3/4 ✓ Branch 0 taken 3 times. ✓ Branch 1 taken 8 times. ✗ Branch 2 not taken. ✓ Branch 3 taken 3 times.	11x	if (outstanding_work_.load(std::memory_order_acquire) == 0 \|\|
923		3x	timeout_us == 0)
924		8x	return 0;
925
926		3x	clear_signal();
927	1/2 ✗ Branch 0 not taken. ✓ Branch 1 taken 3 times.	3x	if (timeout_us < 0)
928		3x	wait_for_signal(lock);
929			else
930		✗	wait_for_signal_for(lock, timeout_us);
931			}
932		1114991x	}
933
934			} // namespace boost::corosio::detail
935
936			#endif // BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SCHEDULER_HPP
937