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/corosio/native/detail/make_err.hpp>
24		#include <boost/capy/error.hpp>
25
26		#include <mutex>
27		#include <tuple>
28
29		#include <errno.h>
30		#include <fcntl.h>
31		#include <signal.h>
32		#include <unistd.h>
33
34		/*
35		POSIX Signal Service
36		====================
37
38		Concrete signal service implementation for POSIX backends. Manages signal
39		registrations via sigaction() and dispatches completions through the
40		scheduler. One instance per execution_context, created by
41		get_signal_service().
42
43		See the block comment further down for the full architecture overview.
44		*/
45
46		/*
47		POSIX Signal Implementation
48		===========================
49
50		This file implements signal handling for POSIX systems using sigaction().
51		The implementation supports signal flags (SA_RESTART, etc.) and integrates
52		with any POSIX-compatible scheduler via the abstract scheduler interface.
53
54		Architecture Overview
55		---------------------
56
57		Three layers manage signal registrations:
58
59		1. signal_state (global singleton)
60		- Tracks the global service list and per-signal registration counts
61		- Stores the flags used for first registration of each signal (for
62		conflict detection when multiple signal_sets register same signal)
63		- Owns the mutex that protects signal handler installation/removal
64
65		2. posix_signal_service (one per execution_context)
66		- Maintains registrations_[] table indexed by signal number
67		- Each slot is a doubly-linked list of signal_registrations for that signal
68		- Also maintains impl_list_ of all posix_signal objects it owns
69
70		3. posix_signal (one per signal_set)
71		- Owns a singly-linked list (sorted by signal number) of signal_registrations
72		- Contains the pending_op_ used for wait operations
73
74		Signal Delivery Flow
75		--------------------
76
77		Delivery uses the self-pipe trick so the signal handler itself performs
78		only async-signal-safe work (mirrors Boost.Asio):
79
80		1. Signal arrives -> corosio_posix_signal_handler(). The handler only
81		write()s the signal number to the global self-pipe (write_fd) and
82		restores errno. No locks, no allocation, no scheduler dispatch.
83
84		2. The read end of the pipe is watched by one backend's event loop
85		(registered via scheduler::register_signal_reader on the first
86		registration). When it becomes readable the backend drains it
87		(drain_signal_pipe) and calls deliver_signal() in normal context.
88
89		3. deliver_signal() iterates all posix_signal_service services:
90		- If a signal_set is waiting (impl->waiting_ == true), post the signal_op
91		to the scheduler for immediate completion
92		- Otherwise, increment reg->undelivered to queue the signal
93
94		4. When wait() is called via start_wait():
95		- First check for queued signals (undelivered > 0); if found, post
96		immediate completion without blocking
97		- Otherwise, set waiting_ = true and call work_started() to keep
98		the io_context alive
99
100		Locking Protocol
101		----------------
102
103		Two mutex levels exist (MUST acquire in this order to avoid deadlock):
104		1. signal_state::mutex - protects handler registration and service list
105		2. posix_signal_service::mutex_ - protects per-service registration tables
106
107		Async-Signal-Safety
108		-------------------
109
110		The C signal handler (corosio_posix_signal_handler) performs only
111		async-signal-safe operations: it reads the single global write_fd and
112		calls write(), saving/restoring errno. It never locks a mutex, allocates
113		memory, or dispatches through the scheduler. All of that happens in
114		deliver_signal(), which runs in normal thread context from the backend
115		event loop after draining the self-pipe. There is therefore no
116		self-deadlock risk if a signal arrives while a thread holds state->mutex
117		or service->mutex_.
118
119		Flag Handling
120		-------------
121
122		- Flags are abstract values in the public API (signal_set::flags_t)
123		- flags_supported() validates that requested flags are available on
124		this platform; returns false if SA_NOCLDWAIT is unavailable and
125		no_child_wait is requested
126		- to_sigaction_flags() maps validated flags to actual SA_* constants
127		- First registration of a signal establishes the flags; subsequent
128		registrations must be compatible (same flags or dont_care)
129		- Requesting unavailable flags returns operation_not_supported
130
131		Work Tracking
132		-------------
133
134		When waiting for a signal:
135		- start_wait() calls sched_->work_started() to prevent io_context::run()
136		from returning while we wait
137		- signal_op::svc is set to point to the service
138		- signal_op::operator()() calls work_finished() after resuming the coroutine
139
140		If a signal was already queued (undelivered > 0), no work tracking is needed
141		because completion is posted immediately.
142		*/
143
144		namespace boost::corosio {
145
146		namespace detail {
147
148		/** Signal service for POSIX backends.
149
150		Manages signal registrations via sigaction() and dispatches signal
151		completions through the scheduler. One instance per execution_context.
152		*/
153		class BOOST_COROSIO_DECL posix_signal_service final
154		: public capy::execution_context::service
155		, public io_object::io_service
156		{
157		public:
158		using key_type = posix_signal_service;
159
160		posix_signal_service(capy::execution_context& ctx, scheduler& sched);
161		~posix_signal_service() override;
162
163		posix_signal_service(posix_signal_service const&) = delete;
164		posix_signal_service& operator=(posix_signal_service const&) = delete;
165
166		io_object::implementation* construct() override;
167
168	141x	void destroy(io_object::implementation* p) override
169		{
170	141x	auto& impl = static_cast<posix_signal&>(*p);
171	141x	[[maybe_unused]] auto n = impl.clear();
172	141x	impl.cancel();
173	141x	destroy_impl(impl);
174	141x	}
175
176		/** Shut down the service.
177
178		Destroys every implementation the service still owns and gives
179		each of their registrations back to the process-global table.
180		*/
181		void shutdown() override;
182
183		void destroy_impl(posix_signal& impl);
184
185		std::error_code add_signal(
186		posix_signal& impl, int signal_number, signal_set::flags_t flags);
187
188		std::error_code remove_signal(posix_signal& impl, int signal_number);
189
190		std::error_code clear_signals(posix_signal& impl);
191
192		void cancel_wait(posix_signal& impl);
193		void start_wait(posix_signal& impl, signal_op* op);
194
195		static void deliver_signal(int signal_number);
196
197		void work_started() noexcept;
198		void work_finished() noexcept;
199		void post(signal_op* op);
200
201		private:
202		static void add_service(posix_signal_service* service);
203		static void remove_service(posix_signal_service* service);
204
205		scheduler* sched_;
206		std::mutex mutex_;
207
208		// Registers the signal self-pipe's read end with sched_ exactly once per
209		// service, so every io_context that waits on a signal can drain the pipe.
210		// A once_flag (not a bool under mutex_) because registration must run
211		// without holding mutex_ or the signal-state mutex — see add_signal.
212		std::mutex reader_mutex_;
213		bool reader_registered_ = false;
214
215		intrusive_list<posix_signal> impl_list_;
216
217		// Per-signal registration table
218		signal_registration* registrations_[max_signal_number];
219
220		// Registration counts for each signal
221		std::size_t registration_count_[max_signal_number];
222
223		// Linked list of all posix_signal_service services for signal delivery
224		posix_signal_service* next_ = nullptr;
225		posix_signal_service* prev_ = nullptr;
226		};
227
228		/** Get or create the signal service for the given context.
229
230		This function is called by the concrete scheduler during initialization
231		to create the signal service with a reference to itself.
232
233		@param ctx Reference to the owning execution_context.
234		@param sched Reference to the scheduler for posting completions.
235		@return Reference to the signal service.
236		*/
237		posix_signal_service&
238		get_signal_service(capy::execution_context& ctx, scheduler& sched);
239
240		} // namespace detail
241
242		} // namespace boost::corosio
243
244		// ---------------------------------------------------------------------------
245		// Inline implementation
246		// ---------------------------------------------------------------------------
247
248		namespace boost::corosio {
249
250		namespace detail {
251
252		namespace posix_signal_detail {
253
254		struct signal_state
255		{
256		std::mutex mutex;
257		posix_signal_service* service_list = nullptr;
258		std::size_t registration_count[max_signal_number] = {};
259		signal_set::flags_t registered_flags[max_signal_number] = {};
260
261		// Self-pipe used to defer signal delivery out of handler context.
262		// The C handler writes the signal number to write_fd (async-signal-
263		// safe); a backend event loop drains read_fd and calls deliver_signal()
264		// in normal context. Created once (on the first signal registration) and
265		// kept for the process lifetime. Each posix_signal_service registers the
266		// read end with its own scheduler (see reader_once_) so every running
267		// io_context can drain it; multiple readers on one pipe are safe because
268		// each signal is a fixed sizeof(int) record read atomically.
269		int read_fd = -1;
270		int write_fd = -1;
271		};
272
273		BOOST_COROSIO_DECL signal_state* get_signal_state();
274
275		// Check if requested flags are supported on this platform.
276		// Returns true if all flags are supported, false otherwise.
277		inline bool
278	162x	flags_supported([[maybe_unused]] signal_set::flags_t flags)
279		{
280		#ifndef SA_NOCLDWAIT
281		if (flags & signal_set::no_child_wait)
282		return false;
283		#endif
284	162x	return true;
285		}
286
287		// Map abstract flags to sigaction() flags.
288		// Caller must ensure flags_supported() returns true first.
289		inline int
290	126x	to_sigaction_flags(signal_set::flags_t flags)
291		{
292	126x	int sa_flags = 0;
293	126x	if (flags & signal_set::restart)
294	23x	sa_flags \|= SA_RESTART;
295	126x	if (flags & signal_set::no_child_stop)
296	1x	sa_flags \|= SA_NOCLDSTOP;
297		#ifdef SA_NOCLDWAIT
298	126x	if (flags & signal_set::no_child_wait)
299	✗	sa_flags \|= SA_NOCLDWAIT;
300		#endif
301	126x	if (flags & signal_set::no_defer)
302	4x	sa_flags \|= SA_NODEFER;
303	126x	if (flags & signal_set::reset_handler)
304	✗	sa_flags \|= SA_RESETHAND;
305	126x	return sa_flags;
306		}
307
308		// Check if two flag values are compatible
309		inline bool
310	27x	flags_compatible(signal_set::flags_t existing, signal_set::flags_t requested)
311		{
312		// dont_care is always compatible
313	52x	if ((existing & signal_set::dont_care) \|\|
314	25x	(requested & signal_set::dont_care))
315	7x	return true;
316
317		// Mask out dont_care bit for comparison
318	20x	constexpr auto mask = ~signal_set::dont_care;
319	20x	return (existing & mask) == (requested & mask);
320		}
321
322		// Lazily create the global signal self-pipe. Idempotent; call under
323		// state->mutex before installing the first signal handler so write_fd is
324		// valid by the time the handler can fire. Both ends are non-blocking and
325		// close-on-exec (mirrors the reactor self-pipe setup in select_scheduler).
326		// Returns the failing call's errno and leaves the fds at -1 if creation
327		// fails: an exhausted descriptor table and a rejected fcntl are different
328		// problems to the caller of add().
329		[[nodiscard]] inline std::error_code
330	162x	open_signal_pipe(signal_state* state)
331		{
332	162x	if (state->read_fd >= 0)
333	148x	return {};
334
335		int fds[2];
336	14x	if (::pipe(fds) < 0)
337	1x	return make_err(errno);
338
339	30x	for (int i = 0; i < 2; ++i)
340		{
341	23x	int fl = ::fcntl(fds[i], F_GETFL, 0);
342	42x	if (fl == -1 \|\| ::fcntl(fds[i], F_SETFL, fl \| O_NONBLOCK) == -1 \|\|
343	19x	::fcntl(fds[i], F_SETFD, FD_CLOEXEC) == -1)
344		{
345	6x	auto ec = make_err(errno);
346	6x	::close(fds[0]);
347	6x	::close(fds[1]);
348	6x	return ec;
349		}
350		}
351
352	7x	state->read_fd = fds[0];
353	7x	state->write_fd = fds[1];
354	7x	return {};
355		}
356
357		// C signal handler. Async-signal-safe: it touches only the single global
358		// write_fd (an int set before any handler is installed) and calls write(),
359		// which POSIX lists as async-signal-safe. errno is saved and restored so an
360		// interrupted foreground syscall is unaffected. A full pipe (write returns
361		// EAGAIN) or a short write is intentionally dropped — the reactor still
362		// coalesces because deliver_signal reports the signal to every waiting set.
363		inline void
364	306x	corosio_posix_signal_handler(int signal_number)
365		{
366	306x	int saved_errno = errno;
367	306x	signal_state* state = get_signal_state();
368		[[maybe_unused]] ssize_t r =
369	306x	::write(state->write_fd, &signal_number, sizeof(int));
370	306x	errno = saved_errno;
371		// With sigaction(), the handler persists automatically (unlike some
372		// signal() implementations that reset to SIG_DFL).
373	306x	}
374
375		// Drain the signal self-pipe and deliver each pending signal. Runs in normal
376		// thread context from the backend event loop, so deliver_signal()'s mutex
377		// locking and scheduler post are safe here. Reads until EAGAIN (edge-
378		// triggered backends require a full drain per readiness event).
379		inline void
380	306x	drain_signal_pipe()
381		{
382	306x	signal_state* state = get_signal_state();
383		int signal_number;
384	612x	while (::read(state->read_fd, &signal_number, sizeof(int)) ==
385		static_cast<ssize_t>(sizeof(int)))
386		{
387	306x	posix_signal_service::deliver_signal(signal_number);
388		}
389	306x	}
390
391		} // namespace posix_signal_detail
392
393		// signal_op implementation
394
395		inline void
396	308x	signal_op::operator()()
397		{
398	308x	if (ec_out)
399	308x	*ec_out = {};
400	308x	if (signal_out)
401	308x	*signal_out = signal_number;
402
403		// Capture svc before resuming (coro may destroy us)
404	308x	auto* service = svc;
405	308x	svc = nullptr;
406
407	308x	cont.h = h;
408	308x	d.post(cont);
409
410		// Balance the work_started() from start_wait
411	308x	if (service)
412	308x	service->work_finished();
413	308x	}
414
415		inline void
416	✗	signal_op::destroy()
417		{
418		// No-op: signal_op is embedded in posix_signal
419	✗	}
420
421		// posix_signal implementation
422
423	147x	inline posix_signal::posix_signal(posix_signal_service& svc) noexcept
424	147x	: svc_(svc)
425		{
426	147x	}
427
428		inline std::coroutine_handle<>
429	323x	posix_signal::wait(
430		std::coroutine_handle<> h,
431		capy::executor_ref d,
432		std::stop_token token,
433		std::error_code* ec,
434		int* signal_out)
435		{
436	323x	pending_op_.h = h;
437	323x	pending_op_.d = d;
438	323x	pending_op_.ec_out = ec;
439	323x	pending_op_.signal_out = signal_out;
440	323x	pending_op_.signal_number = 0;
441
442	323x	if (token.stop_requested())
443		{
444	2x	if (ec)
445	2x	*ec = make_error_code(capy::error::canceled);
446	2x	if (signal_out)
447	2x	*signal_out = 0;
448	2x	pending_op_.cont.h = h;
449	2x	d.post(pending_op_.cont);
450		// completion is always posted to scheduler queue, never inline.
451	2x	return std::noop_coroutine();
452		}
453
454	321x	svc_.start_wait(*this, &pending_op_);
455		// completion is always posted to scheduler queue, never inline.
456	321x	return std::noop_coroutine();
457		}
458
459		inline std::error_code
460	166x	posix_signal::add(int signal_number, signal_set::flags_t flags)
461		{
462	166x	return svc_.add_signal(*this, signal_number, flags);
463		}
464
465		inline std::error_code
466	10x	posix_signal::remove(int signal_number)
467		{
468	10x	return svc_.remove_signal(*this, signal_number);
469		}
470
471		inline std::error_code
472	151x	posix_signal::clear()
473		{
474	151x	return svc_.clear_signals(*this);
475		}
476
477		inline void
478	156x	posix_signal::cancel() noexcept
479		{
480	156x	svc_.cancel_wait(*this);
481	156x	}
482
483		// posix_signal_service implementation
484
485	1790x	inline posix_signal_service::posix_signal_service(
486	1790x	capy::execution_context&, scheduler& sched)
487	1790x	: sched_(&sched)
488		{
489	116350x	for (int i = 0; i < max_signal_number; ++i)
490		{
491	114560x	registrations_[i] = nullptr;
492	114560x	registration_count_[i] = 0;
493		}
494	1790x	add_service(this);
495	1790x	}
496
497	3580x	inline posix_signal_service::~posix_signal_service()
498		{
499	1790x	remove_service(this);
500	3580x	}
501
502		inline void
503	1790x	posix_signal_service::shutdown()
504		{
505		posix_signal_detail::signal_state* state =
506	1790x	posix_signal_detail::get_signal_state();
507	1790x	std::lock_guard state_lock(state->mutex);
508	1790x	std::lock_guard lock(mutex_);
509
510	1796x	for (auto* impl = impl_list_.pop_front(); impl != nullptr;
511	6x	impl = impl_list_.pop_front())
512		{
513	12x	while (auto* reg = impl->signals_)
514		{
515	6x	int const signal_number = reg->signal_number;
516
517		// The registration table outlives every io_context, so a set
518		// still registered here has to give its count and disposition
519		// back the way clear() would: otherwise the signal stays
520		// installed with these flags and the next add() of it is
521		// refused. The per-node table unlink clear() also does is
522		// skipped in favour of the wholesale null-out below.
523	6x	if (state->registration_count[signal_number] == 1)
524		{
525	4x	struct sigaction sa = {};
526	4x	sa.sa_handler = SIG_DFL;
527	4x	sigemptyset(&sa.sa_mask);
528	4x	sa.sa_flags = 0;
529	4x	std::ignore = ::sigaction(signal_number, &sa, nullptr);
530	4x	state->registered_flags[signal_number] = signal_set::none;
531		}
532
533	6x	--state->registration_count[signal_number];
534	6x	--registration_count_[signal_number];
535
536	6x	impl->signals_ = reg->next_in_set;
537	6x	delete reg;
538	6x	}
539	6x	delete impl;
540		}
541
542		// Every live registration hung off an implementation in impl_list_,
543		// so the whole table goes stale at once and can be dropped wholesale
544		// rather than node by node. It has to be dropped: deliver_signal()
545		// walks this service until the destructor unlinks it from the global
546		// list.
547	116350x	for (int i = 0; i < max_signal_number; ++i)
548	114560x	registrations_[i] = nullptr;
549	1790x	}
550
551		inline io_object::implementation*
552	147x	posix_signal_service::construct()
553		{
554	147x	auto* impl = new posix_signal(*this);
555
556		{
557	147x	std::lock_guard lock(mutex_);
558	147x	impl_list_.push_back(impl);
559	147x	}
560
561	147x	return impl;
562		}
563
564		inline void
565	141x	posix_signal_service::destroy_impl(posix_signal& impl)
566		{
567		{
568	141x	std::lock_guard lock(mutex_);
569	141x	impl_list_.remove(&impl);
570	141x	}
571
572	141x	delete &impl;
573	141x	}
574
575		inline std::error_code
576	166x	posix_signal_service::add_signal(
577		posix_signal& impl, int signal_number, signal_set::flags_t flags)
578		{
579	166x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
580	4x	return make_error_code(std::errc::invalid_argument);
581
582		// Validate that requested flags are supported on this platform
583		// (e.g., SA_NOCLDWAIT may not be available on all POSIX systems)
584	162x	if (!posix_signal_detail::flags_supported(flags))
585	✗	return make_error_code(std::errc::operation_not_supported);
586
587		posix_signal_detail::signal_state* state =
588	162x	posix_signal_detail::get_signal_state();
589
590		// Ensure the global self-pipe exists and this service's scheduler is
591		// watching its read end, BEFORE taking the registration locks. The
592		// reactor drain path locks the descriptor mutex and then the signal-state
593		// and service mutexes; register_signal_reader locks the descriptor mutex
594		// (via register_descriptor), so it must run holding neither of those or
595		// the lock order would invert (a real deadlock, caught by TSan). call_once
596		// makes the once-per-service registration safe when two signal_sets on
597		// this context race add() from different threads.
598		{
599	162x	std::lock_guard state_lock(state->mutex);
600	162x	if (auto ec = posix_signal_detail::open_signal_pipe(state))
601	7x	return ec;
602	162x	}
603		{
604		// Success-latched so a failed environmental registration
605		// (epoll_ctl ENOMEM/ENOSPC) is retried by the next add()
606		// instead of being lost; the code travels the return channel.
607	155x	std::lock_guard reg_lock(reader_mutex_);
608	155x	if (!reader_registered_)
609		{
610	108x	if (auto ec = sched_->register_signal_reader(state->read_fd))
611	2x	return ec;
612	106x	reader_registered_ = true;
613		}
614	155x	}
615
616	153x	std::lock_guard state_lock(state->mutex);
617	153x	std::lock_guard lock(mutex_);
618
619		// Find insertion point (list is sorted by signal number)
620	153x	signal_registration** insertion_point = &impl.signals_;
621	153x	signal_registration* reg = impl.signals_;
622	174x	while (reg && reg->signal_number < signal_number)
623		{
624	21x	insertion_point = &reg->next_in_set;
625	21x	reg = reg->next_in_set;
626		}
627
628		// Already registered in this set - check flag compatibility
629		// (same signal_set adding same signal twice with different flags)
630	153x	if (reg && reg->signal_number == signal_number)
631		{
632	13x	if (!posix_signal_detail::flags_compatible(reg->flags, flags))
633	4x	return make_error_code(std::errc::invalid_argument);
634	9x	return {};
635		}
636
637		// Check flag compatibility with global registration
638		// (different signal_set already registered this signal with different flags)
639	140x	if (state->registration_count[signal_number] > 0)
640		{
641	14x	if (!posix_signal_detail::flags_compatible(
642		state->registered_flags[signal_number], flags))
643	2x	return make_error_code(std::errc::invalid_argument);
644		}
645
646	138x	auto* new_reg = new signal_registration;
647	138x	new_reg->signal_number = signal_number;
648	138x	new_reg->flags = flags;
649	138x	new_reg->owner = &impl;
650	138x	new_reg->undelivered = 0;
651
652		// Install signal handler on first global registration
653	138x	if (state->registration_count[signal_number] == 0)
654		{
655	126x	struct sigaction sa = {};
656	126x	sa.sa_handler = posix_signal_detail::corosio_posix_signal_handler;
657	126x	sigemptyset(&sa.sa_mask);
658	126x	sa.sa_flags = posix_signal_detail::to_sigaction_flags(flags);
659
660	126x	if (::sigaction(signal_number, &sa, nullptr) < 0)
661		{
662	1x	delete new_reg;
663	1x	return make_error_code(std::errc::invalid_argument);
664		}
665
666		// Store the flags used for first registration
667	125x	state->registered_flags[signal_number] = flags;
668		}
669
670	137x	new_reg->next_in_set = reg;
671	137x	*insertion_point = new_reg;
672
673	137x	new_reg->next_in_table = registrations_[signal_number];
674	137x	new_reg->prev_in_table = nullptr;
675	137x	if (registrations_[signal_number])
676	10x	registrations_[signal_number]->prev_in_table = new_reg;
677	137x	registrations_[signal_number] = new_reg;
678
679	137x	++state->registration_count[signal_number];
680	137x	++registration_count_[signal_number];
681
682	137x	return {};
683	153x	}
684
685		inline std::error_code
686	10x	posix_signal_service::remove_signal(posix_signal& impl, int signal_number)
687		{
688	10x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
689	2x	return make_error_code(std::errc::invalid_argument);
690
691		posix_signal_detail::signal_state* state =
692	8x	posix_signal_detail::get_signal_state();
693	8x	std::lock_guard state_lock(state->mutex);
694	8x	std::lock_guard lock(mutex_);
695
696	8x	signal_registration** deletion_point = &impl.signals_;
697	8x	signal_registration* reg = impl.signals_;
698	8x	while (reg && reg->signal_number < signal_number)
699		{
700	✗	deletion_point = &reg->next_in_set;
701	✗	reg = reg->next_in_set;
702		}
703
704	8x	if (!reg \|\| reg->signal_number != signal_number)
705	3x	return {};
706
707		// Restore default handler on last global unregistration
708	5x	if (state->registration_count[signal_number] == 1)
709		{
710	5x	struct sigaction sa = {};
711	5x	sa.sa_handler = SIG_DFL;
712	5x	sigemptyset(&sa.sa_mask);
713	5x	sa.sa_flags = 0;
714
715	5x	if (::sigaction(signal_number, &sa, nullptr) < 0)
716	1x	return make_error_code(std::errc::invalid_argument);
717
718		// Clear stored flags
719	4x	state->registered_flags[signal_number] = signal_set::none;
720		}
721
722	4x	*deletion_point = reg->next_in_set;
723
724	4x	if (registrations_[signal_number] == reg)
725	4x	registrations_[signal_number] = reg->next_in_table;
726	4x	if (reg->prev_in_table)
727	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
728	4x	if (reg->next_in_table)
729	✗	reg->next_in_table->prev_in_table = reg->prev_in_table;
730
731	4x	--state->registration_count[signal_number];
732	4x	--registration_count_[signal_number];
733
734	4x	delete reg;
735	4x	return {};
736	8x	}
737
738		inline std::error_code
739	151x	posix_signal_service::clear_signals(posix_signal& impl)
740		{
741		posix_signal_detail::signal_state* state =
742	151x	posix_signal_detail::get_signal_state();
743	151x	std::lock_guard state_lock(state->mutex);
744	151x	std::lock_guard lock(mutex_);
745
746	151x	std::error_code first_error;
747
748	278x	while (signal_registration* reg = impl.signals_)
749		{
750	127x	int signal_number = reg->signal_number;
751
752	127x	if (state->registration_count[signal_number] == 1)
753		{
754	117x	struct sigaction sa = {};
755	117x	sa.sa_handler = SIG_DFL;
756	117x	sigemptyset(&sa.sa_mask);
757	117x	sa.sa_flags = 0;
758
759	117x	if (::sigaction(signal_number, &sa, nullptr) < 0 && !first_error)
760	1x	first_error = make_error_code(std::errc::invalid_argument);
761
762		// Clear stored flags
763	117x	state->registered_flags[signal_number] = signal_set::none;
764		}
765
766	127x	impl.signals_ = reg->next_in_set;
767
768	127x	if (registrations_[signal_number] == reg)
769	127x	registrations_[signal_number] = reg->next_in_table;
770	127x	if (reg->prev_in_table)
771	✗	reg->prev_in_table->next_in_table = reg->next_in_table;
772	127x	if (reg->next_in_table)
773	10x	reg->next_in_table->prev_in_table = reg->prev_in_table;
774
775	127x	--state->registration_count[signal_number];
776	127x	--registration_count_[signal_number];
777
778	127x	delete reg;
779	127x	}
780
781	151x	if (first_error)
782	1x	return first_error;
783	150x	return {};
784	151x	}
785
786		inline void
787	156x	posix_signal_service::cancel_wait(posix_signal& impl)
788		{
789	156x	bool was_waiting = false;
790	156x	signal_op* op = nullptr;
791
792		{
793	156x	std::lock_guard lock(mutex_);
794	156x	impl.cancelled_ = true;
795	156x	if (impl.waiting_)
796		{
797	5x	was_waiting = true;
798	5x	impl.waiting_ = false;
799	5x	op = &impl.pending_op_;
800		}
801	156x	}
802
803	156x	if (was_waiting)
804		{
805	5x	if (op->ec_out)
806	5x	*op->ec_out = make_error_code(capy::error::canceled);
807	5x	if (op->signal_out)
808	5x	*op->signal_out = 0;
809	5x	op->cont.h = op->h;
810	5x	op->d.post(op->cont);
811	5x	sched_->work_finished();
812		}
813	156x	}
814
815		inline void
816	321x	posix_signal_service::start_wait(posix_signal& impl, signal_op* op)
817		{
818		{
819	321x	std::lock_guard lock(mutex_);
820
821		// Check if cancel() was called before this wait started
822	321x	if (impl.cancelled_)
823		{
824	2x	impl.cancelled_ = false;
825	2x	if (op->ec_out)
826	2x	*op->ec_out = make_error_code(capy::error::canceled);
827	2x	if (op->signal_out)
828	2x	*op->signal_out = 0;
829	2x	op->cont.h = op->h;
830	2x	op->d.post(op->cont);
831	2x	return;
832		}
833
834		// Check for queued signals first (signal arrived before wait started)
835	319x	signal_registration* reg = impl.signals_;
836	642x	while (reg)
837		{
838	323x	if (reg->undelivered > 0)
839		{
840	✗	--reg->undelivered;
841	✗	op->signal_number = reg->signal_number;
842		// svc=nullptr: no work_finished needed since we never called work_started
843	✗	op->svc = nullptr;
844	✗	sched_->post(op);
845	✗	return;
846		}
847	323x	reg = reg->next_in_set;
848		}
849
850		// No queued signals - wait for delivery
851	319x	impl.waiting_ = true;
852		// svc=this: signal_op::operator() will call work_finished() to balance this
853	319x	op->svc = this;
854	319x	sched_->work_started();
855	321x	}
856		}
857
858		inline void
859	306x	posix_signal_service::deliver_signal(int signal_number)
860		{
861	306x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
862	✗	return;
863
864		posix_signal_detail::signal_state* state =
865	306x	posix_signal_detail::get_signal_state();
866	306x	std::lock_guard lock(state->mutex);
867
868	306x	posix_signal_service* service = state->service_list;
869	612x	while (service)
870		{
871	306x	std::lock_guard svc_lock(service->mutex_);
872
873	306x	signal_registration* reg = service->registrations_[signal_number];
874	614x	while (reg)
875		{
876	308x	posix_signal* impl = static_cast<posix_signal*>(reg->owner);
877
878	308x	if (impl->waiting_)
879		{
880	308x	impl->waiting_ = false;
881	308x	impl->pending_op_.signal_number = signal_number;
882	308x	service->post(&impl->pending_op_);
883		}
884		else
885		{
886	✗	++reg->undelivered;
887		}
888
889	308x	reg = reg->next_in_table;
890		}
891
892	306x	service = service->next_;
893	306x	}
894	306x	}
895
896		inline void
897		posix_signal_service::work_started() noexcept
898		{
899		sched_->work_started();
900		}
901
902		inline void
903	308x	posix_signal_service::work_finished() noexcept
904		{
905	308x	sched_->work_finished();
906	308x	}
907
908		inline void
909	308x	posix_signal_service::post(signal_op* op)
910		{
911	308x	sched_->post(op);
912	308x	}
913
914		inline void
915	1790x	posix_signal_service::add_service(posix_signal_service* service)
916		{
917		posix_signal_detail::signal_state* state =
918	1790x	posix_signal_detail::get_signal_state();
919	1790x	std::lock_guard lock(state->mutex);
920
921	1790x	service->next_ = state->service_list;
922	1790x	service->prev_ = nullptr;
923	1790x	if (state->service_list)
924	7x	state->service_list->prev_ = service;
925	1790x	state->service_list = service;
926	1790x	}
927
928		inline void
929	1790x	posix_signal_service::remove_service(posix_signal_service* service)
930		{
931		posix_signal_detail::signal_state* state =
932	1790x	posix_signal_detail::get_signal_state();
933	1790x	std::lock_guard lock(state->mutex);
934
935	1790x	if (service->next_ \|\| service->prev_ \|\| state->service_list == service)
936		{
937	1790x	if (state->service_list == service)
938	1790x	state->service_list = service->next_;
939	1790x	if (service->prev_)
940	✗	service->prev_->next_ = service->next_;
941	1790x	if (service->next_)
942	7x	service->next_->prev_ = service->prev_;
943	1790x	service->next_ = nullptr;
944	1790x	service->prev_ = nullptr;
945		}
946	1790x	}
947
948		// get_signal_service - factory function
949
950		inline posix_signal_service&
951	1790x	get_signal_service(capy::execution_context& ctx, scheduler& sched)
952		{
953	1790x	return ctx.make_service<posix_signal_service>(sched);
954		}
955
956		} // namespace detail
957		} // namespace boost::corosio
958
959		#endif // BOOST_COROSIO_POSIX
960
961		#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
962