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	168x	void destroy(io_object::implementation* p) override
167		{
168	168x	auto& impl = static_cast<posix_signal&>(*p);
169	168x	[[maybe_unused]] auto n = impl.clear();
170	168x	impl.cancel();
171	168x	destroy_impl(impl);
172	168x	}
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::once_flag reader_once_;
206
207		intrusive_list<posix_signal> impl_list_;
208
209		// Per-signal registration table
210		signal_registration* registrations_[max_signal_number];
211
212		// Registration counts for each signal
213		std::size_t registration_count_[max_signal_number];
214
215		// Linked list of all posix_signal_service services for signal delivery
216		posix_signal_service* next_ = nullptr;
217		posix_signal_service* prev_ = nullptr;
218		};
219
220		/** Get or create the signal service for the given context.
221
222		This function is called by the concrete scheduler during initialization
223		to create the signal service with a reference to itself.
224
225		@param ctx Reference to the owning execution_context.
226		@param sched Reference to the scheduler for posting completions.
227		@return Reference to the signal service.
228		*/
229		posix_signal_service&
230		get_signal_service(capy::execution_context& ctx, scheduler& sched);
231
232		} // namespace detail
233
234		} // namespace boost::corosio
235
236		// ---------------------------------------------------------------------------
237		// Inline implementation
238		// ---------------------------------------------------------------------------
239
240		namespace boost::corosio {
241
242		namespace detail {
243
244		namespace posix_signal_detail {
245
246		struct signal_state
247		{
248		std::mutex mutex;
249		posix_signal_service* service_list = nullptr;
250		std::size_t registration_count[max_signal_number] = {};
251		signal_set::flags_t registered_flags[max_signal_number] = {};
252
253		// Self-pipe used to defer signal delivery out of handler context.
254		// The C handler writes the signal number to write_fd (async-signal-
255		// safe); a backend event loop drains read_fd and calls deliver_signal()
256		// in normal context. Created once (on the first signal registration) and
257		// kept for the process lifetime. Each posix_signal_service registers the
258		// read end with its own scheduler (see reader_once_) so every running
259		// io_context can drain it; multiple readers on one pipe are safe because
260		// each signal is a fixed sizeof(int) record read atomically.
261		int read_fd = -1;
262		int write_fd = -1;
263		};
264
265		BOOST_COROSIO_DECL signal_state* get_signal_state();
266
267		// Check if requested flags are supported on this platform.
268		// Returns true if all flags are supported, false otherwise.
269		inline bool
270	171x	flags_supported([[maybe_unused]] signal_set::flags_t flags)
271		{
272		#ifndef SA_NOCLDWAIT
273		if (flags & signal_set::no_child_wait)
274		return false;
275		#endif
276	171x	return true;
277		}
278
279		// Map abstract flags to sigaction() flags.
280		// Caller must ensure flags_supported() returns true first.
281		inline int
282	144x	to_sigaction_flags(signal_set::flags_t flags)
283		{
284	144x	int sa_flags = 0;
285	144x	if (flags & signal_set::restart)
286	27x	sa_flags \|= SA_RESTART;
287	144x	if (flags & signal_set::no_child_stop)
288	✗	sa_flags \|= SA_NOCLDSTOP;
289		#ifdef SA_NOCLDWAIT
290	144x	if (flags & signal_set::no_child_wait)
291	✗	sa_flags \|= SA_NOCLDWAIT;
292		#endif
293	144x	if (flags & signal_set::no_defer)
294	3x	sa_flags \|= SA_NODEFER;
295	144x	if (flags & signal_set::reset_handler)
296	✗	sa_flags \|= SA_RESETHAND;
297	144x	return sa_flags;
298		}
299
300		// Check if two flag values are compatible
301		inline bool
302	27x	flags_compatible(signal_set::flags_t existing, signal_set::flags_t requested)
303		{
304		// dont_care is always compatible
305	51x	if ((existing & signal_set::dont_care) \|\|
306	24x	(requested & signal_set::dont_care))
307	9x	return true;
308
309		// Mask out dont_care bit for comparison
310	18x	constexpr auto mask = ~signal_set::dont_care;
311	18x	return (existing & mask) == (requested & mask);
312		}
313
314		// Lazily create the global signal self-pipe. Idempotent; call under
315		// state->mutex before installing the first signal handler so write_fd is
316		// valid by the time the handler can fire. Both ends are non-blocking and
317		// close-on-exec (mirrors the reactor self-pipe setup in select_scheduler).
318		// Returns false and leaves the fds at -1 if creation fails.
319		inline bool
320	171x	open_signal_pipe(signal_state* state)
321		{
322	171x	if (state->read_fd >= 0)
323	169x	return true;
324
325		int fds[2];
326	2x	if (::pipe(fds) < 0)
327	✗	return false;
328
329	6x	for (int i = 0; i < 2; ++i)
330		{
331	4x	int fl = ::fcntl(fds[i], F_GETFL, 0);
332	8x	if (fl == -1 \|\| ::fcntl(fds[i], F_SETFL, fl \| O_NONBLOCK) == -1 \|\|
333	4x	::fcntl(fds[i], F_SETFD, FD_CLOEXEC) == -1)
334		{
335	✗	::close(fds[0]);
336	✗	::close(fds[1]);
337	✗	return false;
338		}
339		}
340
341	2x	state->read_fd = fds[0];
342	2x	state->write_fd = fds[1];
343	2x	return true;
344		}
345
346		// C signal handler. Async-signal-safe: it touches only the single global
347		// write_fd (an int set before any handler is installed) and calls write(),
348		// which POSIX lists as async-signal-safe. errno is saved and restored so an
349		// interrupted foreground syscall is unaffected. A full pipe (write returns
350		// EAGAIN) or a short write is intentionally dropped — the reactor still
351		// coalesces because deliver_signal reports the signal to every waiting set.
352		inline void
353	450x	corosio_posix_signal_handler(int signal_number)
354		{
355	450x	int saved_errno = errno;
356	450x	signal_state* state = get_signal_state();
357		[[maybe_unused]] ssize_t r =
358	450x	::write(state->write_fd, &signal_number, sizeof(int));
359	450x	errno = saved_errno;
360		// With sigaction(), the handler persists automatically (unlike some
361		// signal() implementations that reset to SIG_DFL).
362	450x	}
363
364		// Drain the signal self-pipe and deliver each pending signal. Runs in normal
365		// thread context from the backend event loop, so deliver_signal()'s mutex
366		// locking and scheduler post are safe here. Reads until EAGAIN (edge-
367		// triggered backends require a full drain per readiness event).
368		inline void
369	450x	drain_signal_pipe()
370		{
371	450x	signal_state* state = get_signal_state();
372		int signal_number;
373	900x	while (::read(state->read_fd, &signal_number, sizeof(int)) ==
374		static_cast<ssize_t>(sizeof(int)))
375		{
376	450x	posix_signal_service::deliver_signal(signal_number);
377		}
378	450x	}
379
380		} // namespace posix_signal_detail
381
382		// signal_op implementation
383
384		inline void
385	453x	signal_op::operator()()
386		{
387	453x	if (ec_out)
388	453x	*ec_out = {};
389	453x	if (signal_out)
390	453x	*signal_out = signal_number;
391
392		// Capture svc before resuming (coro may destroy us)
393	453x	auto* service = svc;
394	453x	svc = nullptr;
395
396	453x	cont.h = h;
397	453x	d.post(cont);
398
399		// Balance the work_started() from start_wait
400	453x	if (service)
401	453x	service->work_finished();
402	453x	}
403
404		inline void
405	✗	signal_op::destroy()
406		{
407		// No-op: signal_op is embedded in posix_signal
408	✗	}
409
410		// posix_signal implementation
411
412	168x	inline posix_signal::posix_signal(posix_signal_service& svc) noexcept
413	168x	: svc_(svc)
414		{
415	168x	}
416
417		inline std::coroutine_handle<>
418	465x	posix_signal::wait(
419		std::coroutine_handle<> h,
420		capy::executor_ref d,
421		std::stop_token token,
422		std::error_code* ec,
423		int* signal_out)
424		{
425	465x	pending_op_.h = h;
426	465x	pending_op_.d = d;
427	465x	pending_op_.ec_out = ec;
428	465x	pending_op_.signal_out = signal_out;
429	465x	pending_op_.signal_number = 0;
430
431	465x	if (token.stop_requested())
432		{
433	3x	if (ec)
434	3x	*ec = make_error_code(capy::error::canceled);
435	3x	if (signal_out)
436	3x	*signal_out = 0;
437	3x	pending_op_.cont.h = h;
438	3x	d.post(pending_op_.cont);
439		// completion is always posted to scheduler queue, never inline.
440	3x	return std::noop_coroutine();
441		}
442
443	462x	svc_.start_wait(*this, &pending_op_);
444		// completion is always posted to scheduler queue, never inline.
445	462x	return std::noop_coroutine();
446		}
447
448		inline std::error_code
449	177x	posix_signal::add(int signal_number, signal_set::flags_t flags)
450		{
451	177x	return svc_.add_signal(*this, signal_number, flags);
452		}
453
454		inline std::error_code
455	9x	posix_signal::remove(int signal_number)
456		{
457	9x	return svc_.remove_signal(*this, signal_number);
458		}
459
460		inline std::error_code
461	174x	posix_signal::clear()
462		{
463	174x	return svc_.clear_signals(*this);
464		}
465
466		inline void
467	189x	posix_signal::cancel()
468		{
469	189x	svc_.cancel_wait(*this);
470	189x	}
471
472		// posix_signal_service implementation
473
474	1876x	inline posix_signal_service::posix_signal_service(
475	1876x	capy::execution_context&, scheduler& sched)
476	1876x	: sched_(&sched)
477		{
478	121940x	for (int i = 0; i < max_signal_number; ++i)
479		{
480	120064x	registrations_[i] = nullptr;
481	120064x	registration_count_[i] = 0;
482		}
483	1876x	add_service(this);
484	1876x	}
485
486	3752x	inline posix_signal_service::~posix_signal_service()
487		{
488	1876x	remove_service(this);
489	3752x	}
490
491		inline void
492	1876x	posix_signal_service::shutdown()
493		{
494	1876x	std::lock_guard lock(mutex_);
495
496	1876x	for (auto* impl = impl_list_.pop_front(); impl != nullptr;
497	✗	impl = impl_list_.pop_front())
498		{
499	✗	while (auto* reg = impl->signals_)
500		{
501	✗	impl->signals_ = reg->next_in_set;
502	✗	delete reg;
503	✗	}
504	✗	delete impl;
505		}
506	1876x	}
507
508		inline io_object::implementation*
509	168x	posix_signal_service::construct()
510		{
511	168x	auto* impl = new posix_signal(*this);
512
513		{
514	168x	std::lock_guard lock(mutex_);
515	168x	impl_list_.push_back(impl);
516	168x	}
517
518	168x	return impl;
519		}
520
521		inline void
522	168x	posix_signal_service::destroy_impl(posix_signal& impl)
523		{
524		{
525	168x	std::lock_guard lock(mutex_);
526	168x	impl_list_.remove(&impl);
527	168x	}
528
529	168x	delete &impl;
530	168x	}
531
532		inline std::error_code
533	177x	posix_signal_service::add_signal(
534		posix_signal& impl, int signal_number, signal_set::flags_t flags)
535		{
536	177x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
537	6x	return make_error_code(std::errc::invalid_argument);
538
539		// Validate that requested flags are supported on this platform
540		// (e.g., SA_NOCLDWAIT may not be available on all POSIX systems)
541	171x	if (!posix_signal_detail::flags_supported(flags))
542	✗	return make_error_code(std::errc::operation_not_supported);
543
544		posix_signal_detail::signal_state* state =
545	171x	posix_signal_detail::get_signal_state();
546
547		// Ensure the global self-pipe exists and this service's scheduler is
548		// watching its read end, BEFORE taking the registration locks. The
549		// reactor drain path locks the descriptor mutex and then the signal-state
550		// and service mutexes; register_signal_reader locks the descriptor mutex
551		// (via register_descriptor), so it must run holding neither of those or
552		// the lock order would invert (a real deadlock, caught by TSan). call_once
553		// makes the once-per-service registration safe when two signal_sets on
554		// this context race add() from different threads.
555		{
556	171x	std::lock_guard state_lock(state->mutex);
557	171x	if (!posix_signal_detail::open_signal_pipe(state))
558	✗	return make_error_code(std::errc::io_error);
559	171x	}
560	171x	std::call_once(reader_once_, [this, state] {
561	123x	sched_->register_signal_reader(state->read_fd);
562	123x	});
563
564	171x	std::lock_guard state_lock(state->mutex);
565	171x	std::lock_guard lock(mutex_);
566
567		// Find insertion point (list is sorted by signal number)
568	171x	signal_registration** insertion_point = &impl.signals_;
569	171x	signal_registration* reg = impl.signals_;
570	192x	while (reg && reg->signal_number < signal_number)
571		{
572	21x	insertion_point = &reg->next_in_set;
573	21x	reg = reg->next_in_set;
574		}
575
576		// Already registered in this set - check flag compatibility
577		// (same signal_set adding same signal twice with different flags)
578	171x	if (reg && reg->signal_number == signal_number)
579		{
580	15x	if (!posix_signal_detail::flags_compatible(reg->flags, flags))
581	3x	return make_error_code(std::errc::invalid_argument);
582	12x	return {};
583		}
584
585		// Check flag compatibility with global registration
586		// (different signal_set already registered this signal with different flags)
587	156x	if (state->registration_count[signal_number] > 0)
588		{
589	12x	if (!posix_signal_detail::flags_compatible(
590		state->registered_flags[signal_number], flags))
591	3x	return make_error_code(std::errc::invalid_argument);
592		}
593
594	153x	auto* new_reg = new signal_registration;
595	153x	new_reg->signal_number = signal_number;
596	153x	new_reg->flags = flags;
597	153x	new_reg->owner = &impl;
598	153x	new_reg->undelivered = 0;
599
600		// Install signal handler on first global registration
601	153x	if (state->registration_count[signal_number] == 0)
602		{
603	144x	struct sigaction sa = {};
604	144x	sa.sa_handler = posix_signal_detail::corosio_posix_signal_handler;
605	144x	sigemptyset(&sa.sa_mask);
606	144x	sa.sa_flags = posix_signal_detail::to_sigaction_flags(flags);
607
608	144x	if (::sigaction(signal_number, &sa, nullptr) < 0)
609		{
610	✗	delete new_reg;
611	✗	return make_error_code(std::errc::invalid_argument);
612		}
613
614		// Store the flags used for first registration
615	144x	state->registered_flags[signal_number] = flags;
616		}
617
618	153x	new_reg->next_in_set = reg;
619	153x	*insertion_point = new_reg;
620
621	153x	new_reg->next_in_table = registrations_[signal_number];
622	153x	new_reg->prev_in_table = nullptr;
623	153x	if (registrations_[signal_number])
624	9x	registrations_[signal_number]->prev_in_table = new_reg;
625	153x	registrations_[signal_number] = new_reg;
626
627	153x	++state->registration_count[signal_number];
628	153x	++registration_count_[signal_number];
629
630	153x	return {};
631	171x	}
632
633		inline std::error_code
634	9x	posix_signal_service::remove_signal(posix_signal& impl, int signal_number)
635		{
636	9x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
637	3x	return make_error_code(std::errc::invalid_argument);
638
639		posix_signal_detail::signal_state* state =
640	6x	posix_signal_detail::get_signal_state();
641	6x	std::lock_guard state_lock(state->mutex);
642	6x	std::lock_guard lock(mutex_);
643
644	6x	signal_registration** deletion_point = &impl.signals_;
645	6x	signal_registration* reg = impl.signals_;
646	6x	while (reg && reg->signal_number < signal_number)
647		{
648	✗	deletion_point = &reg->next_in_set;
649	✗	reg = reg->next_in_set;
650		}
651
652	6x	if (!reg \|\| reg->signal_number != signal_number)
653	3x	return {};
654
655		// Restore default handler on last global unregistration
656	3x	if (state->registration_count[signal_number] == 1)
657		{
658	3x	struct sigaction sa = {};
659	3x	sa.sa_handler = SIG_DFL;
660	3x	sigemptyset(&sa.sa_mask);
661	3x	sa.sa_flags = 0;
662
663	3x	if (::sigaction(signal_number, &sa, nullptr) < 0)
664	✗	return make_error_code(std::errc::invalid_argument);
665
666		// Clear stored flags
667	3x	state->registered_flags[signal_number] = signal_set::none;
668		}
669
670	3x	*deletion_point = reg->next_in_set;
671
672	3x	if (registrations_[signal_number] == reg)
673	3x	registrations_[signal_number] = reg->next_in_table;
674	3x	if (reg->prev_in_table)
675	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
676	3x	if (reg->next_in_table)
677	✗	reg->next_in_table->prev_in_table = reg->prev_in_table;
678
679	3x	--state->registration_count[signal_number];
680	3x	--registration_count_[signal_number];
681
682	3x	delete reg;
683	3x	return {};
684	6x	}
685
686		inline std::error_code
687	174x	posix_signal_service::clear_signals(posix_signal& impl)
688		{
689		posix_signal_detail::signal_state* state =
690	174x	posix_signal_detail::get_signal_state();
691	174x	std::lock_guard state_lock(state->mutex);
692	174x	std::lock_guard lock(mutex_);
693
694	174x	std::error_code first_error;
695
696	324x	while (signal_registration* reg = impl.signals_)
697		{
698	150x	int signal_number = reg->signal_number;
699
700	150x	if (state->registration_count[signal_number] == 1)
701		{
702	141x	struct sigaction sa = {};
703	141x	sa.sa_handler = SIG_DFL;
704	141x	sigemptyset(&sa.sa_mask);
705	141x	sa.sa_flags = 0;
706
707	141x	if (::sigaction(signal_number, &sa, nullptr) < 0 && !first_error)
708	✗	first_error = make_error_code(std::errc::invalid_argument);
709
710		// Clear stored flags
711	141x	state->registered_flags[signal_number] = signal_set::none;
712		}
713
714	150x	impl.signals_ = reg->next_in_set;
715
716	150x	if (registrations_[signal_number] == reg)
717	150x	registrations_[signal_number] = reg->next_in_table;
718	150x	if (reg->prev_in_table)
719	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
720	150x	if (reg->next_in_table)
721	9x	reg->next_in_table->prev_in_table = reg->prev_in_table;
722
723	150x	--state->registration_count[signal_number];
724	150x	--registration_count_[signal_number];
725
726	150x	delete reg;
727	150x	}
728
729	174x	if (first_error)
730	✗	return first_error;
731	174x	return {};
732	174x	}
733
734		inline void
735	189x	posix_signal_service::cancel_wait(posix_signal& impl)
736		{
737	189x	bool was_waiting = false;
738	189x	signal_op* op = nullptr;
739
740		{
741	189x	std::lock_guard lock(mutex_);
742	189x	impl.cancelled_ = true;
743	189x	if (impl.waiting_)
744		{
745	6x	was_waiting = true;
746	6x	impl.waiting_ = false;
747	6x	op = &impl.pending_op_;
748		}
749	189x	}
750
751	189x	if (was_waiting)
752		{
753	6x	if (op->ec_out)
754	6x	*op->ec_out = make_error_code(capy::error::canceled);
755	6x	if (op->signal_out)
756	6x	*op->signal_out = 0;
757	6x	op->cont.h = op->h;
758	6x	op->d.post(op->cont);
759	6x	sched_->work_finished();
760		}
761	189x	}
762
763		inline void
764	462x	posix_signal_service::start_wait(posix_signal& impl, signal_op* op)
765		{
766		{
767	462x	std::lock_guard lock(mutex_);
768
769		// Check if cancel() was called before this wait started
770	462x	if (impl.cancelled_)
771		{
772	3x	impl.cancelled_ = false;
773	3x	if (op->ec_out)
774	3x	*op->ec_out = make_error_code(capy::error::canceled);
775	3x	if (op->signal_out)
776	3x	*op->signal_out = 0;
777	3x	op->cont.h = op->h;
778	3x	op->d.post(op->cont);
779	3x	return;
780		}
781
782		// Check for queued signals first (signal arrived before wait started)
783	459x	signal_registration* reg = impl.signals_;
784	921x	while (reg)
785		{
786	462x	if (reg->undelivered > 0)
787		{
788	✗	--reg->undelivered;
789	✗	op->signal_number = reg->signal_number;
790		// svc=nullptr: no work_finished needed since we never called work_started
791	✗	op->svc = nullptr;
792	✗	sched_->post(op);
793	✗	return;
794		}
795	462x	reg = reg->next_in_set;
796		}
797
798		// No queued signals - wait for delivery
799	459x	impl.waiting_ = true;
800		// svc=this: signal_op::operator() will call work_finished() to balance this
801	459x	op->svc = this;
802	459x	sched_->work_started();
803	462x	}
804		}
805
806		inline void
807	450x	posix_signal_service::deliver_signal(int signal_number)
808		{
809	450x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
810	✗	return;
811
812		posix_signal_detail::signal_state* state =
813	450x	posix_signal_detail::get_signal_state();
814	450x	std::lock_guard lock(state->mutex);
815
816	450x	posix_signal_service* service = state->service_list;
817	900x	while (service)
818		{
819	450x	std::lock_guard svc_lock(service->mutex_);
820
821	450x	signal_registration* reg = service->registrations_[signal_number];
822	903x	while (reg)
823		{
824	453x	posix_signal* impl = static_cast<posix_signal*>(reg->owner);
825
826	453x	if (impl->waiting_)
827		{
828	453x	impl->waiting_ = false;
829	453x	impl->pending_op_.signal_number = signal_number;
830	453x	service->post(&impl->pending_op_);
831		}
832		else
833		{
834	✗	++reg->undelivered;
835		}
836
837	453x	reg = reg->next_in_table;
838		}
839
840	450x	service = service->next_;
841	450x	}
842	450x	}
843
844		inline void
845		posix_signal_service::work_started() noexcept
846		{
847		sched_->work_started();
848		}
849
850		inline void
851	453x	posix_signal_service::work_finished() noexcept
852		{
853	453x	sched_->work_finished();
854	453x	}
855
856		inline void
857	453x	posix_signal_service::post(signal_op* op)
858		{
859	453x	sched_->post(op);
860	453x	}
861
862		inline void
863	1876x	posix_signal_service::add_service(posix_signal_service* service)
864		{
865		posix_signal_detail::signal_state* state =
866	1876x	posix_signal_detail::get_signal_state();
867	1876x	std::lock_guard lock(state->mutex);
868
869	1876x	service->next_ = state->service_list;
870	1876x	service->prev_ = nullptr;
871	1876x	if (state->service_list)
872	7x	state->service_list->prev_ = service;
873	1876x	state->service_list = service;
874	1876x	}
875
876		inline void
877	1876x	posix_signal_service::remove_service(posix_signal_service* service)
878		{
879		posix_signal_detail::signal_state* state =
880	1876x	posix_signal_detail::get_signal_state();
881	1876x	std::lock_guard lock(state->mutex);
882
883	1876x	if (service->next_ \|\| service->prev_ \|\| state->service_list == service)
884		{
885	1876x	if (state->service_list == service)
886	1876x	state->service_list = service->next_;
887	1876x	if (service->prev_)
888	✗	service->prev_->next_ = service->next_;
889	1876x	if (service->next_)
890	7x	service->next_->prev_ = service->prev_;
891	1876x	service->next_ = nullptr;
892	1876x	service->prev_ = nullptr;
893		}
894	1876x	}
895
896		// get_signal_service - factory function
897
898		inline posix_signal_service&
899	1876x	get_signal_service(capy::execution_context& ctx, scheduler& sched)
900		{
901	1876x	return ctx.make_service<posix_signal_service>(sched);
902		}
903
904		} // namespace detail
905		} // namespace boost::corosio
906
907		#endif // BOOST_COROSIO_POSIX
908
909		#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
910