include/boost/corosio/native/detail/posix/posix_signal_service.hpp

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posix_signal_service.hpp

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1		//
2		// Copyright (c) 2026 Steve Gerbino
3		// Copyright (c) 2026 Michael Vandeberg
4		//
5		// Distributed under the Boost Software License, Version 1.0. (See accompanying
6		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7		//
8		// Official repository: https://github.com/cppalliance/corosio
9		//
10
11		#ifndef BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
12		#define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
13
14		#include <boost/corosio/detail/platform.hpp>
15
16		#if BOOST_COROSIO_POSIX
17
18		#include <boost/corosio/native/detail/posix/posix_signal.hpp>
19
20		#include <boost/corosio/detail/config.hpp>
21		#include <boost/capy/ex/execution_context.hpp>
22		#include <boost/corosio/detail/scheduler.hpp>
23		#include <boost/capy/error.hpp>
24
25		#include <mutex>
26
27		#include <errno.h>
28		#include <fcntl.h>
29		#include <signal.h>
30		#include <unistd.h>
31
32		/*
33		POSIX Signal Service
34		====================
35
36		Concrete signal service implementation for POSIX backends. Manages signal
37		registrations via sigaction() and dispatches completions through the
38		scheduler. One instance per execution_context, created by
39		get_signal_service().
40
41		See the block comment further down for the full architecture overview.
42		*/
43
44		/*
45		POSIX Signal Implementation
46		===========================
47
48		This file implements signal handling for POSIX systems using sigaction().
49		The implementation supports signal flags (SA_RESTART, etc.) and integrates
50		with any POSIX-compatible scheduler via the abstract scheduler interface.
51
52		Architecture Overview
53		---------------------
54
55		Three layers manage signal registrations:
56
57		1. signal_state (global singleton)
58		- Tracks the global service list and per-signal registration counts
59		- Stores the flags used for first registration of each signal (for
60		conflict detection when multiple signal_sets register same signal)
61		- Owns the mutex that protects signal handler installation/removal
62
63		2. posix_signal_service (one per execution_context)
64		- Maintains registrations_[] table indexed by signal number
65		- Each slot is a doubly-linked list of signal_registrations for that signal
66		- Also maintains impl_list_ of all posix_signal objects it owns
67
68		3. posix_signal (one per signal_set)
69		- Owns a singly-linked list (sorted by signal number) of signal_registrations
70		- Contains the pending_op_ used for wait operations
71
72		Signal Delivery Flow
73		--------------------
74
75		Delivery uses the self-pipe trick so the signal handler itself performs
76		only async-signal-safe work (mirrors Boost.Asio):
77
78		1. Signal arrives -> corosio_posix_signal_handler(). The handler only
79		write()s the signal number to the global self-pipe (write_fd) and
80		restores errno. No locks, no allocation, no scheduler dispatch.
81
82		2. The read end of the pipe is watched by one backend's event loop
83		(registered via scheduler::register_signal_reader on the first
84		registration). When it becomes readable the backend drains it
85		(drain_signal_pipe) and calls deliver_signal() in normal context.
86
87		3. deliver_signal() iterates all posix_signal_service services:
88		- If a signal_set is waiting (impl->waiting_ == true), post the signal_op
89		to the scheduler for immediate completion
90		- Otherwise, increment reg->undelivered to queue the signal
91
92		4. When wait() is called via start_wait():
93		- First check for queued signals (undelivered > 0); if found, post
94		immediate completion without blocking
95		- Otherwise, set waiting_ = true and call work_started() to keep
96		the io_context alive
97
98		Locking Protocol
99		----------------
100
101		Two mutex levels exist (MUST acquire in this order to avoid deadlock):
102		1. signal_state::mutex - protects handler registration and service list
103		2. posix_signal_service::mutex_ - protects per-service registration tables
104
105		Async-Signal-Safety
106		-------------------
107
108		The C signal handler (corosio_posix_signal_handler) performs only
109		async-signal-safe operations: it reads the single global write_fd and
110		calls write(), saving/restoring errno. It never locks a mutex, allocates
111		memory, or dispatches through the scheduler. All of that happens in
112		deliver_signal(), which runs in normal thread context from the backend
113		event loop after draining the self-pipe. There is therefore no
114		self-deadlock risk if a signal arrives while a thread holds state->mutex
115		or service->mutex_.
116
117		Flag Handling
118		-------------
119
120		- Flags are abstract values in the public API (signal_set::flags_t)
121		- flags_supported() validates that requested flags are available on
122		this platform; returns false if SA_NOCLDWAIT is unavailable and
123		no_child_wait is requested
124		- to_sigaction_flags() maps validated flags to actual SA_* constants
125		- First registration of a signal establishes the flags; subsequent
126		registrations must be compatible (same flags or dont_care)
127		- Requesting unavailable flags returns operation_not_supported
128
129		Work Tracking
130		-------------
131
132		When waiting for a signal:
133		- start_wait() calls sched_->work_started() to prevent io_context::run()
134		from returning while we wait
135		- signal_op::svc is set to point to the service
136		- signal_op::operator()() calls work_finished() after resuming the coroutine
137
138		If a signal was already queued (undelivered > 0), no work tracking is needed
139		because completion is posted immediately.
140		*/
141
142		namespace boost::corosio {
143
144		namespace detail {
145
146		/** Signal service for POSIX backends.
147
148		Manages signal registrations via sigaction() and dispatches signal
149		completions through the scheduler. One instance per execution_context.
150		*/
151		class BOOST_COROSIO_DECL posix_signal_service final
152		: public capy::execution_context::service
153		, public io_object::io_service
154		{
155		public:
156		using key_type = posix_signal_service;
157
158		posix_signal_service(capy::execution_context& ctx, scheduler& sched);
159		~posix_signal_service() override;
160
161		posix_signal_service(posix_signal_service const&) = delete;
162		posix_signal_service& operator=(posix_signal_service const&) = delete;
163
164		io_object::implementation* construct() override;
165
166	181x	void destroy(io_object::implementation* p) override
167		{
168	181x	auto& impl = static_cast<posix_signal&>(*p);
169	181x	[[maybe_unused]] auto n = impl.clear();
170	181x	impl.cancel();
171	181x	destroy_impl(impl);
172	181x	}
173
174		void shutdown() override;
175
176		void destroy_impl(posix_signal& impl);
177
178		std::error_code add_signal(
179		posix_signal& impl, int signal_number, signal_set::flags_t flags);
180
181		std::error_code remove_signal(posix_signal& impl, int signal_number);
182
183		std::error_code clear_signals(posix_signal& impl);
184
185		void cancel_wait(posix_signal& impl);
186		void start_wait(posix_signal& impl, signal_op* op);
187
188		static void deliver_signal(int signal_number);
189
190		void work_started() noexcept;
191		void work_finished() noexcept;
192		void post(signal_op* op);
193
194		private:
195		static void add_service(posix_signal_service* service);
196		static void remove_service(posix_signal_service* service);
197
198		scheduler* sched_;
199		std::mutex mutex_;
200
201		// Registers the signal self-pipe's read end with sched_ exactly once per
202		// service, so every io_context that waits on a signal can drain the pipe.
203		// A once_flag (not a bool under mutex_) because registration must run
204		// without holding mutex_ or the signal-state mutex — see add_signal.
205		std::mutex reader_mutex_;
206		bool reader_registered_ = false;
207
208		intrusive_list<posix_signal> impl_list_;
209
210		// Per-signal registration table
211		signal_registration* registrations_[max_signal_number];
212
213		// Registration counts for each signal
214		std::size_t registration_count_[max_signal_number];
215
216		// Linked list of all posix_signal_service services for signal delivery
217		posix_signal_service* next_ = nullptr;
218		posix_signal_service* prev_ = nullptr;
219		};
220
221		/** Get or create the signal service for the given context.
222
223		This function is called by the concrete scheduler during initialization
224		to create the signal service with a reference to itself.
225
226		@param ctx Reference to the owning execution_context.
227		@param sched Reference to the scheduler for posting completions.
228		@return Reference to the signal service.
229		*/
230		posix_signal_service&
231		get_signal_service(capy::execution_context& ctx, scheduler& sched);
232
233		} // namespace detail
234
235		} // namespace boost::corosio
236
237		// ---------------------------------------------------------------------------
238		// Inline implementation
239		// ---------------------------------------------------------------------------
240
241		namespace boost::corosio {
242
243		namespace detail {
244
245		namespace posix_signal_detail {
246
247		struct signal_state
248		{
249		std::mutex mutex;
250		posix_signal_service* service_list = nullptr;
251		std::size_t registration_count[max_signal_number] = {};
252		signal_set::flags_t registered_flags[max_signal_number] = {};
253
254		// Self-pipe used to defer signal delivery out of handler context.
255		// The C handler writes the signal number to write_fd (async-signal-
256		// safe); a backend event loop drains read_fd and calls deliver_signal()
257		// in normal context. Created once (on the first signal registration) and
258		// kept for the process lifetime. Each posix_signal_service registers the
259		// read end with its own scheduler (see reader_once_) so every running
260		// io_context can drain it; multiple readers on one pipe are safe because
261		// each signal is a fixed sizeof(int) record read atomically.
262		int read_fd = -1;
263		int write_fd = -1;
264		};
265
266		BOOST_COROSIO_DECL signal_state* get_signal_state();
267
268		// Check if requested flags are supported on this platform.
269		// Returns true if all flags are supported, false otherwise.
270		inline bool
271	195x	flags_supported([[maybe_unused]] signal_set::flags_t flags)
272		{
273		#ifndef SA_NOCLDWAIT
274		if (flags & signal_set::no_child_wait)
275		return false;
276		#endif
277	195x	return true;
278		}
279
280		// Map abstract flags to sigaction() flags.
281		// Caller must ensure flags_supported() returns true first.
282		inline int
283	161x	to_sigaction_flags(signal_set::flags_t flags)
284		{
285	161x	int sa_flags = 0;
286	161x	if (flags & signal_set::restart)
287	30x	sa_flags \|= SA_RESTART;
288	161x	if (flags & signal_set::no_child_stop)
289	1x	sa_flags \|= SA_NOCLDSTOP;
290		#ifdef SA_NOCLDWAIT
291	161x	if (flags & signal_set::no_child_wait)
292	✗	sa_flags \|= SA_NOCLDWAIT;
293		#endif
294	161x	if (flags & signal_set::no_defer)
295	3x	sa_flags \|= SA_NODEFER;
296	161x	if (flags & signal_set::reset_handler)
297	✗	sa_flags \|= SA_RESETHAND;
298	161x	return sa_flags;
299		}
300
301		// Check if two flag values are compatible
302		inline bool
303	34x	flags_compatible(signal_set::flags_t existing, signal_set::flags_t requested)
304		{
305		// dont_care is always compatible
306	65x	if ((existing & signal_set::dont_care) \|\|
307	31x	(requested & signal_set::dont_care))
308	10x	return true;
309
310		// Mask out dont_care bit for comparison
311	24x	constexpr auto mask = ~signal_set::dont_care;
312	24x	return (existing & mask) == (requested & mask);
313		}
314
315		// Lazily create the global signal self-pipe. Idempotent; call under
316		// state->mutex before installing the first signal handler so write_fd is
317		// valid by the time the handler can fire. Both ends are non-blocking and
318		// close-on-exec (mirrors the reactor self-pipe setup in select_scheduler).
319		// Returns false and leaves the fds at -1 if creation fails.
320		inline bool
321	195x	open_signal_pipe(signal_state* state)
322		{
323	195x	if (state->read_fd >= 0)
324	192x	return true;
325
326		int fds[2];
327	3x	if (::pipe(fds) < 0)
328	✗	return false;
329
330	9x	for (int i = 0; i < 2; ++i)
331		{
332	6x	int fl = ::fcntl(fds[i], F_GETFL, 0);
333	12x	if (fl == -1 \|\| ::fcntl(fds[i], F_SETFL, fl \| O_NONBLOCK) == -1 \|\|
334	6x	::fcntl(fds[i], F_SETFD, FD_CLOEXEC) == -1)
335		{
336	✗	::close(fds[0]);
337	✗	::close(fds[1]);
338	✗	return false;
339		}
340		}
341
342	3x	state->read_fd = fds[0];
343	3x	state->write_fd = fds[1];
344	3x	return true;
345		}
346
347		// C signal handler. Async-signal-safe: it touches only the single global
348		// write_fd (an int set before any handler is installed) and calls write(),
349		// which POSIX lists as async-signal-safe. errno is saved and restored so an
350		// interrupted foreground syscall is unaffected. A full pipe (write returns
351		// EAGAIN) or a short write is intentionally dropped — the reactor still
352		// coalesces because deliver_signal reports the signal to every waiting set.
353		inline void
354	452x	corosio_posix_signal_handler(int signal_number)
355		{
356	452x	int saved_errno = errno;
357	452x	signal_state* state = get_signal_state();
358		[[maybe_unused]] ssize_t r =
359	452x	::write(state->write_fd, &signal_number, sizeof(int));
360	452x	errno = saved_errno;
361		// With sigaction(), the handler persists automatically (unlike some
362		// signal() implementations that reset to SIG_DFL).
363	452x	}
364
365		// Drain the signal self-pipe and deliver each pending signal. Runs in normal
366		// thread context from the backend event loop, so deliver_signal()'s mutex
367		// locking and scheduler post are safe here. Reads until EAGAIN (edge-
368		// triggered backends require a full drain per readiness event).
369		inline void
370	452x	drain_signal_pipe()
371		{
372	452x	signal_state* state = get_signal_state();
373		int signal_number;
374	904x	while (::read(state->read_fd, &signal_number, sizeof(int)) ==
375		static_cast<ssize_t>(sizeof(int)))
376		{
377	452x	posix_signal_service::deliver_signal(signal_number);
378		}
379	452x	}
380
381		} // namespace posix_signal_detail
382
383		// signal_op implementation
384
385		inline void
386	455x	signal_op::operator()()
387		{
388	455x	if (ec_out)
389	455x	*ec_out = {};
390	455x	if (signal_out)
391	455x	*signal_out = signal_number;
392
393		// Capture svc before resuming (coro may destroy us)
394	455x	auto* service = svc;
395	455x	svc = nullptr;
396
397	455x	cont.h = h;
398	455x	d.post(cont);
399
400		// Balance the work_started() from start_wait
401	455x	if (service)
402	455x	service->work_finished();
403	455x	}
404
405		inline void
406	✗	signal_op::destroy()
407		{
408		// No-op: signal_op is embedded in posix_signal
409	✗	}
410
411		// posix_signal implementation
412
413	181x	inline posix_signal::posix_signal(posix_signal_service& svc) noexcept
414	181x	: svc_(svc)
415		{
416	181x	}
417
418		inline std::coroutine_handle<>
419	468x	posix_signal::wait(
420		std::coroutine_handle<> h,
421		capy::executor_ref d,
422		std::stop_token token,
423		std::error_code* ec,
424		int* signal_out)
425		{
426	468x	pending_op_.h = h;
427	468x	pending_op_.d = d;
428	468x	pending_op_.ec_out = ec;
429	468x	pending_op_.signal_out = signal_out;
430	468x	pending_op_.signal_number = 0;
431
432	468x	if (token.stop_requested())
433		{
434	3x	if (ec)
435	3x	*ec = make_error_code(capy::error::canceled);
436	3x	if (signal_out)
437	3x	*signal_out = 0;
438	3x	pending_op_.cont.h = h;
439	3x	d.post(pending_op_.cont);
440		// completion is always posted to scheduler queue, never inline.
441	3x	return std::noop_coroutine();
442		}
443
444	465x	svc_.start_wait(*this, &pending_op_);
445		// completion is always posted to scheduler queue, never inline.
446	465x	return std::noop_coroutine();
447		}
448
449		inline std::error_code
450	201x	posix_signal::add(int signal_number, signal_set::flags_t flags)
451		{
452	201x	return svc_.add_signal(*this, signal_number, flags);
453		}
454
455		inline std::error_code
456	11x	posix_signal::remove(int signal_number)
457		{
458	11x	return svc_.remove_signal(*this, signal_number);
459		}
460
461		inline std::error_code
462	188x	posix_signal::clear()
463		{
464	188x	return svc_.clear_signals(*this);
465		}
466
467		inline void
468	203x	posix_signal::cancel() noexcept
469		{
470	203x	svc_.cancel_wait(*this);
471	203x	}
472
473		// posix_signal_service implementation
474
475	2603x	inline posix_signal_service::posix_signal_service(
476	2603x	capy::execution_context&, scheduler& sched)
477	2603x	: sched_(&sched)
478		{
479	169195x	for (int i = 0; i < max_signal_number; ++i)
480		{
481	166592x	registrations_[i] = nullptr;
482	166592x	registration_count_[i] = 0;
483		}
484	2603x	add_service(this);
485	2603x	}
486
487	5206x	inline posix_signal_service::~posix_signal_service()
488		{
489	2603x	remove_service(this);
490	5206x	}
491
492		inline void
493	2603x	posix_signal_service::shutdown()
494		{
495	2603x	std::lock_guard lock(mutex_);
496
497	2603x	for (auto* impl = impl_list_.pop_front(); impl != nullptr;
498	✗	impl = impl_list_.pop_front())
499		{
500	✗	while (auto* reg = impl->signals_)
501		{
502	✗	impl->signals_ = reg->next_in_set;
503	✗	delete reg;
504	✗	}
505	✗	delete impl;
506		}
507	2603x	}
508
509		inline io_object::implementation*
510	181x	posix_signal_service::construct()
511		{
512	181x	auto* impl = new posix_signal(*this);
513
514		{
515	181x	std::lock_guard lock(mutex_);
516	181x	impl_list_.push_back(impl);
517	181x	}
518
519	181x	return impl;
520		}
521
522		inline void
523	181x	posix_signal_service::destroy_impl(posix_signal& impl)
524		{
525		{
526	181x	std::lock_guard lock(mutex_);
527	181x	impl_list_.remove(&impl);
528	181x	}
529
530	181x	delete &impl;
531	181x	}
532
533		inline std::error_code
534	201x	posix_signal_service::add_signal(
535		posix_signal& impl, int signal_number, signal_set::flags_t flags)
536		{
537	201x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
538	6x	return make_error_code(std::errc::invalid_argument);
539
540		// Validate that requested flags are supported on this platform
541		// (e.g., SA_NOCLDWAIT may not be available on all POSIX systems)
542	195x	if (!posix_signal_detail::flags_supported(flags))
543	✗	return make_error_code(std::errc::operation_not_supported);
544
545		posix_signal_detail::signal_state* state =
546	195x	posix_signal_detail::get_signal_state();
547
548		// Ensure the global self-pipe exists and this service's scheduler is
549		// watching its read end, BEFORE taking the registration locks. The
550		// reactor drain path locks the descriptor mutex and then the signal-state
551		// and service mutexes; register_signal_reader locks the descriptor mutex
552		// (via register_descriptor), so it must run holding neither of those or
553		// the lock order would invert (a real deadlock, caught by TSan). call_once
554		// makes the once-per-service registration safe when two signal_sets on
555		// this context race add() from different threads.
556		{
557	195x	std::lock_guard state_lock(state->mutex);
558	195x	if (!posix_signal_detail::open_signal_pipe(state))
559	✗	return make_error_code(std::errc::io_error);
560	195x	}
561		{
562		// Success-latched so a failed environmental registration
563		// (epoll_ctl ENOMEM/ENOSPC) is retried by the next add()
564		// instead of being lost; the code travels the return channel.
565	195x	std::lock_guard reg_lock(reader_mutex_);
566	195x	if (!reader_registered_)
567		{
568	133x	if (auto ec = sched_->register_signal_reader(state->read_fd))
569	✗	return ec;
570	133x	reader_registered_ = true;
571		}
572	195x	}
573
574	195x	std::lock_guard state_lock(state->mutex);
575	195x	std::lock_guard lock(mutex_);
576
577		// Find insertion point (list is sorted by signal number)
578	195x	signal_registration** insertion_point = &impl.signals_;
579	195x	signal_registration* reg = impl.signals_;
580	223x	while (reg && reg->signal_number < signal_number)
581		{
582	28x	insertion_point = &reg->next_in_set;
583	28x	reg = reg->next_in_set;
584		}
585
586		// Already registered in this set - check flag compatibility
587		// (same signal_set adding same signal twice with different flags)
588	195x	if (reg && reg->signal_number == signal_number)
589		{
590	18x	if (!posix_signal_detail::flags_compatible(reg->flags, flags))
591	5x	return make_error_code(std::errc::invalid_argument);
592	13x	return {};
593		}
594
595		// Check flag compatibility with global registration
596		// (different signal_set already registered this signal with different flags)
597	177x	if (state->registration_count[signal_number] > 0)
598		{
599	16x	if (!posix_signal_detail::flags_compatible(
600		state->registered_flags[signal_number], flags))
601	3x	return make_error_code(std::errc::invalid_argument);
602		}
603
604	174x	auto* new_reg = new signal_registration;
605	174x	new_reg->signal_number = signal_number;
606	174x	new_reg->flags = flags;
607	174x	new_reg->owner = &impl;
608	174x	new_reg->undelivered = 0;
609
610		// Install signal handler on first global registration
611	174x	if (state->registration_count[signal_number] == 0)
612		{
613	161x	struct sigaction sa = {};
614	161x	sa.sa_handler = posix_signal_detail::corosio_posix_signal_handler;
615	161x	sigemptyset(&sa.sa_mask);
616	161x	sa.sa_flags = posix_signal_detail::to_sigaction_flags(flags);
617
618	161x	if (::sigaction(signal_number, &sa, nullptr) < 0)
619		{
620	✗	delete new_reg;
621	✗	return make_error_code(std::errc::invalid_argument);
622		}
623
624		// Store the flags used for first registration
625	161x	state->registered_flags[signal_number] = flags;
626		}
627
628	174x	new_reg->next_in_set = reg;
629	174x	*insertion_point = new_reg;
630
631	174x	new_reg->next_in_table = registrations_[signal_number];
632	174x	new_reg->prev_in_table = nullptr;
633	174x	if (registrations_[signal_number])
634	13x	registrations_[signal_number]->prev_in_table = new_reg;
635	174x	registrations_[signal_number] = new_reg;
636
637	174x	++state->registration_count[signal_number];
638	174x	++registration_count_[signal_number];
639
640	174x	return {};
641	195x	}
642
643		inline std::error_code
644	11x	posix_signal_service::remove_signal(posix_signal& impl, int signal_number)
645		{
646	11x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
647	3x	return make_error_code(std::errc::invalid_argument);
648
649		posix_signal_detail::signal_state* state =
650	8x	posix_signal_detail::get_signal_state();
651	8x	std::lock_guard state_lock(state->mutex);
652	8x	std::lock_guard lock(mutex_);
653
654	8x	signal_registration** deletion_point = &impl.signals_;
655	8x	signal_registration* reg = impl.signals_;
656	8x	while (reg && reg->signal_number < signal_number)
657		{
658	✗	deletion_point = &reg->next_in_set;
659	✗	reg = reg->next_in_set;
660		}
661
662	8x	if (!reg \|\| reg->signal_number != signal_number)
663	4x	return {};
664
665		// Restore default handler on last global unregistration
666	4x	if (state->registration_count[signal_number] == 1)
667		{
668	4x	struct sigaction sa = {};
669	4x	sa.sa_handler = SIG_DFL;
670	4x	sigemptyset(&sa.sa_mask);
671	4x	sa.sa_flags = 0;
672
673	4x	if (::sigaction(signal_number, &sa, nullptr) < 0)
674	✗	return make_error_code(std::errc::invalid_argument);
675
676		// Clear stored flags
677	4x	state->registered_flags[signal_number] = signal_set::none;
678		}
679
680	4x	*deletion_point = reg->next_in_set;
681
682	4x	if (registrations_[signal_number] == reg)
683	4x	registrations_[signal_number] = reg->next_in_table;
684	4x	if (reg->prev_in_table)
685	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
686	4x	if (reg->next_in_table)
687	✗	reg->next_in_table->prev_in_table = reg->prev_in_table;
688
689	4x	--state->registration_count[signal_number];
690	4x	--registration_count_[signal_number];
691
692	4x	delete reg;
693	4x	return {};
694	8x	}
695
696		inline std::error_code
697	188x	posix_signal_service::clear_signals(posix_signal& impl)
698		{
699		posix_signal_detail::signal_state* state =
700	188x	posix_signal_detail::get_signal_state();
701	188x	std::lock_guard state_lock(state->mutex);
702	188x	std::lock_guard lock(mutex_);
703
704	188x	std::error_code first_error;
705
706	358x	while (signal_registration* reg = impl.signals_)
707		{
708	170x	int signal_number = reg->signal_number;
709
710	170x	if (state->registration_count[signal_number] == 1)
711		{
712	157x	struct sigaction sa = {};
713	157x	sa.sa_handler = SIG_DFL;
714	157x	sigemptyset(&sa.sa_mask);
715	157x	sa.sa_flags = 0;
716
717	157x	if (::sigaction(signal_number, &sa, nullptr) < 0 && !first_error)
718	✗	first_error = make_error_code(std::errc::invalid_argument);
719
720		// Clear stored flags
721	157x	state->registered_flags[signal_number] = signal_set::none;
722		}
723
724	170x	impl.signals_ = reg->next_in_set;
725
726	170x	if (registrations_[signal_number] == reg)
727	170x	registrations_[signal_number] = reg->next_in_table;
728	170x	if (reg->prev_in_table)
729	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
730	170x	if (reg->next_in_table)
731	13x	reg->next_in_table->prev_in_table = reg->prev_in_table;
732
733	170x	--state->registration_count[signal_number];
734	170x	--registration_count_[signal_number];
735
736	170x	delete reg;
737	170x	}
738
739	188x	if (first_error)
740	✗	return first_error;
741	188x	return {};
742	188x	}
743
744		inline void
745	203x	posix_signal_service::cancel_wait(posix_signal& impl)
746		{
747	203x	bool was_waiting = false;
748	203x	signal_op* op = nullptr;
749
750		{
751	203x	std::lock_guard lock(mutex_);
752	203x	impl.cancelled_ = true;
753	203x	if (impl.waiting_)
754		{
755	7x	was_waiting = true;
756	7x	impl.waiting_ = false;
757	7x	op = &impl.pending_op_;
758		}
759	203x	}
760
761	203x	if (was_waiting)
762		{
763	7x	if (op->ec_out)
764	7x	*op->ec_out = make_error_code(capy::error::canceled);
765	7x	if (op->signal_out)
766	7x	*op->signal_out = 0;
767	7x	op->cont.h = op->h;
768	7x	op->d.post(op->cont);
769	7x	sched_->work_finished();
770		}
771	203x	}
772
773		inline void
774	465x	posix_signal_service::start_wait(posix_signal& impl, signal_op* op)
775		{
776		{
777	465x	std::lock_guard lock(mutex_);
778
779		// Check if cancel() was called before this wait started
780	465x	if (impl.cancelled_)
781		{
782	3x	impl.cancelled_ = false;
783	3x	if (op->ec_out)
784	3x	*op->ec_out = make_error_code(capy::error::canceled);
785	3x	if (op->signal_out)
786	3x	*op->signal_out = 0;
787	3x	op->cont.h = op->h;
788	3x	op->d.post(op->cont);
789	3x	return;
790		}
791
792		// Check for queued signals first (signal arrived before wait started)
793	462x	signal_registration* reg = impl.signals_;
794	929x	while (reg)
795		{
796	467x	if (reg->undelivered > 0)
797		{
798	✗	--reg->undelivered;
799	✗	op->signal_number = reg->signal_number;
800		// svc=nullptr: no work_finished needed since we never called work_started
801	✗	op->svc = nullptr;
802	✗	sched_->post(op);
803	✗	return;
804		}
805	467x	reg = reg->next_in_set;
806		}
807
808		// No queued signals - wait for delivery
809	462x	impl.waiting_ = true;
810		// svc=this: signal_op::operator() will call work_finished() to balance this
811	462x	op->svc = this;
812	462x	sched_->work_started();
813	465x	}
814		}
815
816		inline void
817	452x	posix_signal_service::deliver_signal(int signal_number)
818		{
819	452x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
820	✗	return;
821
822		posix_signal_detail::signal_state* state =
823	452x	posix_signal_detail::get_signal_state();
824	452x	std::lock_guard lock(state->mutex);
825
826	452x	posix_signal_service* service = state->service_list;
827	904x	while (service)
828		{
829	452x	std::lock_guard svc_lock(service->mutex_);
830
831	452x	signal_registration* reg = service->registrations_[signal_number];
832	907x	while (reg)
833		{
834	455x	posix_signal* impl = static_cast<posix_signal*>(reg->owner);
835
836	455x	if (impl->waiting_)
837		{
838	455x	impl->waiting_ = false;
839	455x	impl->pending_op_.signal_number = signal_number;
840	455x	service->post(&impl->pending_op_);
841		}
842		else
843		{
844	✗	++reg->undelivered;
845		}
846
847	455x	reg = reg->next_in_table;
848		}
849
850	452x	service = service->next_;
851	452x	}
852	452x	}
853
854		inline void
855		posix_signal_service::work_started() noexcept
856		{
857		sched_->work_started();
858		}
859
860		inline void
861	455x	posix_signal_service::work_finished() noexcept
862		{
863	455x	sched_->work_finished();
864	455x	}
865
866		inline void
867	455x	posix_signal_service::post(signal_op* op)
868		{
869	455x	sched_->post(op);
870	455x	}
871
872		inline void
873	2603x	posix_signal_service::add_service(posix_signal_service* service)
874		{
875		posix_signal_detail::signal_state* state =
876	2603x	posix_signal_detail::get_signal_state();
877	2603x	std::lock_guard lock(state->mutex);
878
879	2603x	service->next_ = state->service_list;
880	2603x	service->prev_ = nullptr;
881	2603x	if (state->service_list)
882	7x	state->service_list->prev_ = service;
883	2603x	state->service_list = service;
884	2603x	}
885
886		inline void
887	2603x	posix_signal_service::remove_service(posix_signal_service* service)
888		{
889		posix_signal_detail::signal_state* state =
890	2603x	posix_signal_detail::get_signal_state();
891	2603x	std::lock_guard lock(state->mutex);
892
893	2603x	if (service->next_ \|\| service->prev_ \|\| state->service_list == service)
894		{
895	2603x	if (state->service_list == service)
896	2603x	state->service_list = service->next_;
897	2603x	if (service->prev_)
898	✗	service->prev_->next_ = service->next_;
899	2603x	if (service->next_)
900	7x	service->next_->prev_ = service->prev_;
901	2603x	service->next_ = nullptr;
902	2603x	service->prev_ = nullptr;
903		}
904	2603x	}
905
906		// get_signal_service - factory function
907
908		inline posix_signal_service&
909	2603x	get_signal_service(capy::execution_context& ctx, scheduler& sched)
910		{
911	2603x	return ctx.make_service<posix_signal_service>(sched);
912		}
913
914		} // namespace detail
915		} // namespace boost::corosio
916
917		#endif // BOOST_COROSIO_POSIX
918
919		#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
920