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	184x	void destroy(io_object::implementation* p) override
169		{
170	184x	auto& impl = static_cast<posix_signal&>(*p);
171	184x	[[maybe_unused]] auto n = impl.clear();
172	184x	impl.disarm_stop();
173	184x	impl.cancel();
174	184x	destroy_impl(impl);
175	184x	}
176
177		/** Shut down the service.
178
179		Destroys every implementation the service still owns and gives
180		each of their registrations back to the process-global table.
181		*/
182		void shutdown() override;
183
184		void destroy_impl(posix_signal& impl);
185
186		std::error_code add_signal(
187		posix_signal& impl, int signal_number, signal_set::flags_t flags);
188
189		std::error_code remove_signal(posix_signal& impl, int signal_number);
190
191		std::error_code clear_signals(posix_signal& impl);
192
193		void cancel_wait(posix_signal& impl);
194		void start_wait(posix_signal& impl, signal_op* op);
195
196		/** Cancel an in-flight wait on behalf of a stop token.
197
198		Identical to @ref cancel_wait except that it does not set the
199		sticky `cancelled_` latch: a stop token scopes to one operation,
200		so a request arriving after the wait completed must do nothing.
201		*/
202		void cancel_wait_token(posix_signal& impl) noexcept;
203
204		/** Clear the per-operation stop flag before a new wait arms.
205
206		Lives here rather than on the implementation because `mutex_` is
207		the service's; the service is a friend of `posix_signal`, not the
208		reverse.
209		*/
210	985x	void reset_token_cancel(posix_signal& impl) noexcept
211		{
212	985x	std::lock_guard lock(mutex_);
213	985x	impl.token_cancelled_ = false;
214	985x	}
215
216		static void deliver_signal(int signal_number);
217
218		void work_started() noexcept;
219		void work_finished() noexcept;
220		void post(signal_op* op);
221
222		private:
223		static void add_service(posix_signal_service* service);
224		static void remove_service(posix_signal_service* service);
225
226		scheduler* sched_;
227		std::mutex mutex_;
228
229		// Registers the signal self-pipe's read end with sched_ exactly once per
230		// service, so every io_context that waits on a signal can drain the pipe.
231		// A once_flag (not a bool under mutex_) because registration must run
232		// without holding mutex_ or the signal-state mutex — see add_signal.
233		std::mutex reader_mutex_;
234		bool reader_registered_ = false;
235
236		intrusive_list<posix_signal> impl_list_;
237
238		// Per-signal registration table
239		signal_registration* registrations_[max_signal_number];
240
241		// Registration counts for each signal
242		std::size_t registration_count_[max_signal_number];
243
244		// Linked list of all posix_signal_service services for signal delivery
245		posix_signal_service* next_ = nullptr;
246		posix_signal_service* prev_ = nullptr;
247		};
248
249		/** Get or create the signal service for the given context.
250
251		This function is called by the concrete scheduler during initialization
252		to create the signal service with a reference to itself.
253
254		@param ctx Reference to the owning execution_context.
255		@param sched Reference to the scheduler for posting completions.
256		@return Reference to the signal service.
257		*/
258		posix_signal_service&
259		get_signal_service(capy::execution_context& ctx, scheduler& sched);
260
261		} // namespace detail
262
263		} // namespace boost::corosio
264
265		// ---------------------------------------------------------------------------
266		// Inline implementation
267		// ---------------------------------------------------------------------------
268
269		namespace boost::corosio {
270
271		namespace detail {
272
273		namespace posix_signal_detail {
274
275		struct signal_state
276		{
277		std::mutex mutex;
278		posix_signal_service* service_list = nullptr;
279		std::size_t registration_count[max_signal_number] = {};
280		signal_set::flags_t registered_flags[max_signal_number] = {};
281
282		// Self-pipe used to defer signal delivery out of handler context.
283		// The C handler writes the signal number to write_fd (async-signal-
284		// safe); a backend event loop drains read_fd and calls deliver_signal()
285		// in normal context. Created once (on the first signal registration) and
286		// kept for the process lifetime. Each posix_signal_service registers the
287		// read end with its own scheduler (see reader_once_) so every running
288		// io_context can drain it; multiple readers on one pipe are safe because
289		// each signal is a fixed sizeof(int) record read atomically.
290		int read_fd = -1;
291		int write_fd = -1;
292		};
293
294		BOOST_COROSIO_DECL signal_state* get_signal_state();
295
296		// Check if requested flags are supported on this platform.
297		// Returns true if all flags are supported, false otherwise.
298		inline bool
299	207x	flags_supported([[maybe_unused]] signal_set::flags_t flags)
300		{
301		#ifndef SA_NOCLDWAIT
302		if (flags & signal_set::no_child_wait)
303		return false;
304		#endif
305	207x	return true;
306		}
307
308		// Map abstract flags to sigaction() flags.
309		// Caller must ensure flags_supported() returns true first.
310		inline int
311	159x	to_sigaction_flags(signal_set::flags_t flags)
312		{
313	159x	int sa_flags = 0;
314	159x	if (flags & signal_set::restart)
315	23x	sa_flags \|= SA_RESTART;
316	159x	if (flags & signal_set::no_child_stop)
317	3x	sa_flags \|= SA_NOCLDSTOP;
318		#ifdef SA_NOCLDWAIT
319	159x	if (flags & signal_set::no_child_wait)
320	2x	sa_flags \|= SA_NOCLDWAIT;
321		#endif
322	159x	if (flags & signal_set::no_defer)
323	4x	sa_flags \|= SA_NODEFER;
324	159x	if (flags & signal_set::reset_handler)
325	2x	sa_flags \|= SA_RESETHAND;
326	159x	return sa_flags;
327		}
328
329		// Check if two flag values are compatible
330		inline bool
331	39x	flags_compatible(signal_set::flags_t existing, signal_set::flags_t requested)
332		{
333		// dont_care is always compatible
334	76x	if ((existing & signal_set::dont_care) \|\|
335	37x	(requested & signal_set::dont_care))
336	7x	return true;
337
338		// Mask out dont_care bit for comparison
339	32x	constexpr auto mask = ~signal_set::dont_care;
340	32x	return (existing & mask) == (requested & mask);
341		}
342
343		// Lazily create the global signal self-pipe. Idempotent; call under
344		// state->mutex before installing the first signal handler so write_fd is
345		// valid by the time the handler can fire. Both ends are non-blocking and
346		// close-on-exec (mirrors the reactor self-pipe setup in select_scheduler).
347		// Returns the failing call's errno and leaves the fds at -1 if creation
348		// fails: an exhausted descriptor table and a rejected fcntl are different
349		// problems to the caller of add().
350		[[nodiscard]] inline std::error_code
351	207x	open_signal_pipe(signal_state* state)
352		{
353	207x	if (state->read_fd >= 0)
354	193x	return {};
355
356		int fds[2];
357	14x	if (::pipe(fds) < 0)
358	1x	return make_err(errno);
359
360	30x	for (int i = 0; i < 2; ++i)
361		{
362	23x	int fl = ::fcntl(fds[i], F_GETFL, 0);
363	42x	if (fl == -1 \|\| ::fcntl(fds[i], F_SETFL, fl \| O_NONBLOCK) == -1 \|\|
364	19x	::fcntl(fds[i], F_SETFD, FD_CLOEXEC) == -1)
365		{
366	6x	auto ec = make_err(errno);
367	6x	::close(fds[0]);
368	6x	::close(fds[1]);
369	6x	return ec;
370		}
371		}
372
373	7x	state->read_fd = fds[0];
374	7x	state->write_fd = fds[1];
375	7x	return {};
376		}
377
378		// C signal handler. Async-signal-safe: it touches only the single global
379		// write_fd (an int set before any handler is installed) and calls write(),
380		// which POSIX lists as async-signal-safe. errno is saved and restored so an
381		// interrupted foreground syscall is unaffected. A full pipe (write returns
382		// EAGAIN) or a short write is intentionally dropped — the reactor still
383		// coalesces because deliver_signal reports the signal to every waiting set.
384		inline void
385	317x	corosio_posix_signal_handler(int signal_number)
386		{
387	317x	int saved_errno = errno;
388	317x	signal_state* state = get_signal_state();
389		[[maybe_unused]] ssize_t r =
390	317x	::write(state->write_fd, &signal_number, sizeof(int));
391	317x	errno = saved_errno;
392		// With sigaction(), the handler persists automatically (unlike some
393		// signal() implementations that reset to SIG_DFL).
394	317x	}
395
396		// Drain the signal self-pipe and deliver each pending signal. Runs in normal
397		// thread context from the backend event loop, so deliver_signal()'s mutex
398		// locking and scheduler post are safe here. Reads until EAGAIN (edge-
399		// triggered backends require a full drain per readiness event).
400		inline void
401	317x	drain_signal_pipe()
402		{
403	317x	signal_state* state = get_signal_state();
404		int signal_number;
405	634x	while (::read(state->read_fd, &signal_number, sizeof(int)) ==
406		static_cast<ssize_t>(sizeof(int)))
407		{
408	317x	posix_signal_service::deliver_signal(signal_number);
409		}
410	317x	}
411
412		} // namespace posix_signal_detail
413
414		// signal_op implementation
415
416		inline void
417	321x	signal_op::operator()()
418		{
419	321x	if (ec_out)
420	321x	*ec_out = {};
421	321x	if (signal_out)
422	321x	*signal_out = signal_number;
423
424		// Capture svc before resuming (coro may destroy us)
425	321x	auto* service = svc;
426	321x	svc = nullptr;
427
428	321x	cont.h = h;
429	321x	d.post(cont);
430
431		// Balance the work_started() from start_wait
432	321x	if (service)
433	319x	service->work_finished();
434	321x	}
435
436		inline void
437	✗	signal_op::destroy()
438		{
439		// No-op: signal_op is embedded in posix_signal
440	✗	}
441
442		// posix_signal implementation
443
444	190x	inline posix_signal::posix_signal(posix_signal_service& svc) noexcept
445	190x	: svc_(svc)
446		{
447	190x	}
448
449		inline std::coroutine_handle<>
450	1106x	posix_signal::wait(
451		std::coroutine_handle<> h,
452		capy::executor_ref d,
453		std::stop_token token,
454		std::error_code* ec,
455		int* signal_out)
456		{
457	1106x	pending_op_.h = h;
458	1106x	pending_op_.d = d;
459	1106x	pending_op_.ec_out = ec;
460	1106x	pending_op_.signal_out = signal_out;
461	1106x	pending_op_.signal_number = 0;
462
463		// Disarm any callback left over from a previous wait before doing
464		// anything else, including the early return below: otherwise that
465		// path leaves this object owning a callback it no longer uses.
466		// Outside start_wait's lock on purpose: ~stop_callback blocks until a
467		// concurrently running callback returns, and that callback takes
468		// posix_signal_service::mutex_.
469	1106x	stop_cb_.reset();
470
471	1106x	if (token.stop_requested())
472		{
473	121x	if (ec)
474	121x	*ec = make_error_code(capy::error::canceled);
475	121x	if (signal_out)
476	121x	*signal_out = 0;
477	121x	pending_op_.cont.h = h;
478	121x	d.post(pending_op_.cont);
479		// completion is always posted to scheduler queue, never inline.
480	121x	return std::noop_coroutine();
481		}
482
483		// Clearing the flag before arming is load-bearing: reset_token_cancel
484		// must run immediately before emplace, not before the early return
485		// above.
486	985x	svc_.reset_token_cancel(*this);
487	985x	if (token.stop_possible())
488	655x	stop_cb_.emplace(token, token_canceller{this});
489
490	985x	svc_.start_wait(*this, &pending_op_);
491		// completion is always posted to scheduler queue, never inline.
492	985x	return std::noop_coroutine();
493		}
494
495		inline std::error_code
496	211x	posix_signal::add(int signal_number, signal_set::flags_t flags)
497		{
498	211x	return svc_.add_signal(*this, signal_number, flags);
499		}
500
501		inline std::error_code
502	26x	posix_signal::remove(int signal_number)
503		{
504	26x	return svc_.remove_signal(*this, signal_number);
505		}
506
507		inline std::error_code
508	198x	posix_signal::clear()
509		{
510	198x	return svc_.clear_signals(*this);
511		}
512
513		inline void
514	201x	posix_signal::cancel() noexcept
515		{
516	201x	svc_.cancel_wait(*this);
517	201x	}
518
519		// posix_signal_service implementation
520
521	2241x	inline posix_signal_service::posix_signal_service(
522	2241x	capy::execution_context&, scheduler& sched)
523	2241x	: sched_(&sched)
524		{
525	145665x	for (int i = 0; i < max_signal_number; ++i)
526		{
527	143424x	registrations_[i] = nullptr;
528	143424x	registration_count_[i] = 0;
529		}
530	2241x	add_service(this);
531	2241x	}
532
533	4482x	inline posix_signal_service::~posix_signal_service()
534		{
535	2241x	remove_service(this);
536	4482x	}
537
538		inline void
539	2241x	posix_signal_service::shutdown()
540		{
541		// Collected under the locks below and deleted after they are released:
542		// ~posix_signal destroys an armed stop_cb_, and ~stop_callback blocks
543		// until a concurrently running token_canceller returns -- which takes
544		// mutex_. Deleting while still holding mutex_ would self-deadlock the
545		// same way disarm_stop() would if called inside the locked loop.
546	2241x	intrusive_list<posix_signal> doomed;
547
548		{
549		posix_signal_detail::signal_state* state =
550	2241x	posix_signal_detail::get_signal_state();
551	2241x	std::lock_guard state_lock(state->mutex);
552	2241x	std::lock_guard lock(mutex_);
553
554	2247x	for (auto* impl = impl_list_.pop_front(); impl != nullptr;
555	6x	impl = impl_list_.pop_front())
556		{
557	12x	while (auto* reg = impl->signals_)
558		{
559	6x	int const signal_number = reg->signal_number;
560
561		// The registration table outlives every io_context, so a set
562		// still registered here has to give its count and disposition
563		// back the way clear() would: otherwise the signal stays
564		// installed with these flags and the next add() of it is
565		// refused. The per-node table unlink clear() also does is
566		// skipped in favour of the wholesale null-out below.
567	6x	if (state->registration_count[signal_number] == 1)
568		{
569	4x	struct sigaction sa = {};
570	4x	sa.sa_handler = SIG_DFL;
571	4x	sigemptyset(&sa.sa_mask);
572	4x	sa.sa_flags = 0;
573	4x	std::ignore = ::sigaction(signal_number, &sa, nullptr);
574	4x	state->registered_flags[signal_number] = signal_set::none;
575		}
576
577	6x	--state->registration_count[signal_number];
578	6x	--registration_count_[signal_number];
579
580	6x	impl->signals_ = reg->next_in_set;
581	6x	delete reg;
582	6x	}
583	6x	doomed.push_back(impl);
584		}
585
586		// Every live registration hung off an implementation in impl_list_,
587		// so the whole table goes stale at once and can be dropped wholesale
588		// rather than node by node. It has to be dropped: deliver_signal()
589		// walks this service until the destructor unlinks it from the global
590		// list.
591	145665x	for (int i = 0; i < max_signal_number; ++i)
592	143424x	registrations_[i] = nullptr;
593	2241x	}
594
595	2247x	for (auto* impl = doomed.pop_front(); impl != nullptr;
596	6x	impl = doomed.pop_front())
597		{
598	6x	delete impl;
599		}
600	2241x	}
601
602		inline io_object::implementation*
603	190x	posix_signal_service::construct()
604		{
605	190x	auto* impl = new posix_signal(*this);
606
607		{
608	190x	std::lock_guard lock(mutex_);
609	190x	impl_list_.push_back(impl);
610	190x	}
611
612	190x	return impl;
613		}
614
615		inline void
616	184x	posix_signal_service::destroy_impl(posix_signal& impl)
617		{
618		{
619	184x	std::lock_guard lock(mutex_);
620	184x	impl_list_.remove(&impl);
621	184x	}
622
623	184x	delete &impl;
624	184x	}
625
626		inline std::error_code
627	211x	posix_signal_service::add_signal(
628		posix_signal& impl, int signal_number, signal_set::flags_t flags)
629		{
630	211x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
631	4x	return make_error_code(std::errc::invalid_argument);
632
633		// Validate that requested flags are supported on this platform
634		// (e.g., SA_NOCLDWAIT may not be available on all POSIX systems)
635	207x	if (!posix_signal_detail::flags_supported(flags))
636	✗	return make_error_code(std::errc::operation_not_supported);
637
638		posix_signal_detail::signal_state* state =
639	207x	posix_signal_detail::get_signal_state();
640
641		// Ensure the global self-pipe exists and this service's scheduler is
642		// watching its read end, BEFORE taking the registration locks. The
643		// reactor drain path locks the descriptor mutex and then the signal-state
644		// and service mutexes; register_signal_reader locks the descriptor mutex
645		// (via register_descriptor), so it must run holding neither of those or
646		// the lock order would invert (a real deadlock, caught by TSan). call_once
647		// makes the once-per-service registration safe when two signal_sets on
648		// this context race add() from different threads.
649		{
650	207x	std::lock_guard state_lock(state->mutex);
651	207x	if (auto ec = posix_signal_detail::open_signal_pipe(state))
652	7x	return ec;
653	207x	}
654		{
655		// Success-latched so a failed environmental registration
656		// (epoll_ctl ENOMEM/ENOSPC) is retried by the next add()
657		// instead of being lost; the code travels the return channel.
658	200x	std::lock_guard reg_lock(reader_mutex_);
659	200x	if (!reader_registered_)
660		{
661	137x	if (auto ec = sched_->register_signal_reader(state->read_fd))
662	2x	return ec;
663	135x	reader_registered_ = true;
664		}
665	200x	}
666
667	198x	std::lock_guard state_lock(state->mutex);
668	198x	std::lock_guard lock(mutex_);
669
670		// Find insertion point (list is sorted by signal number)
671	198x	signal_registration** insertion_point = &impl.signals_;
672	198x	signal_registration* reg = impl.signals_;
673	221x	while (reg && reg->signal_number < signal_number)
674		{
675	23x	insertion_point = &reg->next_in_set;
676	23x	reg = reg->next_in_set;
677		}
678
679		// Already registered in this set - check flag compatibility
680		// (same signal_set adding same signal twice with different flags)
681	198x	if (reg && reg->signal_number == signal_number)
682		{
683	13x	if (!posix_signal_detail::flags_compatible(reg->flags, flags))
684	4x	return make_error_code(std::errc::invalid_argument);
685	9x	return {};
686		}
687
688		// Check flag compatibility with global registration
689		// (different signal_set already registered this signal with different flags)
690	185x	if (state->registration_count[signal_number] > 0)
691		{
692	26x	if (!posix_signal_detail::flags_compatible(
693		state->registered_flags[signal_number], flags))
694	2x	return make_error_code(std::errc::invalid_argument);
695		}
696
697	183x	auto* new_reg = new signal_registration;
698	183x	new_reg->signal_number = signal_number;
699	183x	new_reg->flags = flags;
700	183x	new_reg->owner = &impl;
701	183x	new_reg->undelivered = 0;
702
703		// Install signal handler on first global registration
704	183x	if (state->registration_count[signal_number] == 0)
705		{
706	159x	struct sigaction sa = {};
707	159x	sa.sa_handler = posix_signal_detail::corosio_posix_signal_handler;
708	159x	sigemptyset(&sa.sa_mask);
709	159x	sa.sa_flags = posix_signal_detail::to_sigaction_flags(flags);
710
711	159x	if (::sigaction(signal_number, &sa, nullptr) < 0)
712		{
713	1x	delete new_reg;
714	1x	return make_error_code(std::errc::invalid_argument);
715		}
716
717		// Store the flags used for first registration
718	158x	state->registered_flags[signal_number] = flags;
719		}
720
721	182x	new_reg->next_in_set = reg;
722	182x	*insertion_point = new_reg;
723
724	182x	new_reg->next_in_table = registrations_[signal_number];
725	182x	new_reg->prev_in_table = nullptr;
726	182x	if (registrations_[signal_number])
727	18x	registrations_[signal_number]->prev_in_table = new_reg;
728	182x	registrations_[signal_number] = new_reg;
729
730	182x	++state->registration_count[signal_number];
731	182x	++registration_count_[signal_number];
732
733	182x	return {};
734	198x	}
735
736		inline std::error_code
737	26x	posix_signal_service::remove_signal(posix_signal& impl, int signal_number)
738		{
739	26x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
740	2x	return make_error_code(std::errc::invalid_argument);
741
742		posix_signal_detail::signal_state* state =
743	24x	posix_signal_detail::get_signal_state();
744	24x	std::lock_guard state_lock(state->mutex);
745	24x	std::lock_guard lock(mutex_);
746
747	24x	signal_registration** deletion_point = &impl.signals_;
748	24x	signal_registration* reg = impl.signals_;
749	26x	while (reg && reg->signal_number < signal_number)
750		{
751	2x	deletion_point = &reg->next_in_set;
752	2x	reg = reg->next_in_set;
753		}
754
755	24x	if (!reg \|\| reg->signal_number != signal_number)
756	3x	return {};
757
758		// Restore default handler on last global unregistration
759	21x	if (state->registration_count[signal_number] == 1)
760		{
761	17x	struct sigaction sa = {};
762	17x	sa.sa_handler = SIG_DFL;
763	17x	sigemptyset(&sa.sa_mask);
764	17x	sa.sa_flags = 0;
765
766	17x	if (::sigaction(signal_number, &sa, nullptr) < 0)
767	1x	return make_error_code(std::errc::invalid_argument);
768
769		// Clear stored flags
770	16x	state->registered_flags[signal_number] = signal_set::none;
771		}
772
773	20x	*deletion_point = reg->next_in_set;
774
775	20x	if (registrations_[signal_number] == reg)
776	18x	registrations_[signal_number] = reg->next_in_table;
777	20x	if (reg->prev_in_table)
778	2x	reg->prev_in_table->next_in_table = reg->next_in_table;
779	20x	if (reg->next_in_table)
780	2x	reg->next_in_table->prev_in_table = reg->prev_in_table;
781
782	20x	--state->registration_count[signal_number];
783	20x	--registration_count_[signal_number];
784
785	20x	delete reg;
786	20x	return {};
787	24x	}
788
789		inline std::error_code
790	198x	posix_signal_service::clear_signals(posix_signal& impl)
791		{
792		posix_signal_detail::signal_state* state =
793	198x	posix_signal_detail::get_signal_state();
794	198x	std::lock_guard state_lock(state->mutex);
795	198x	std::lock_guard lock(mutex_);
796
797	198x	std::error_code first_error;
798
799	354x	while (signal_registration* reg = impl.signals_)
800		{
801	156x	int signal_number = reg->signal_number;
802
803	156x	if (state->registration_count[signal_number] == 1)
804		{
805	138x	struct sigaction sa = {};
806	138x	sa.sa_handler = SIG_DFL;
807	138x	sigemptyset(&sa.sa_mask);
808	138x	sa.sa_flags = 0;
809
810	138x	if (::sigaction(signal_number, &sa, nullptr) < 0 && !first_error)
811	1x	first_error = make_error_code(std::errc::invalid_argument);
812
813		// Clear stored flags
814	138x	state->registered_flags[signal_number] = signal_set::none;
815		}
816
817	156x	impl.signals_ = reg->next_in_set;
818
819	156x	if (registrations_[signal_number] == reg)
820	154x	registrations_[signal_number] = reg->next_in_table;
821	156x	if (reg->prev_in_table)
822	2x	reg->prev_in_table->next_in_table = reg->next_in_table;
823	156x	if (reg->next_in_table)
824	12x	reg->next_in_table->prev_in_table = reg->prev_in_table;
825
826	156x	--state->registration_count[signal_number];
827	156x	--registration_count_[signal_number];
828
829	156x	delete reg;
830	156x	}
831
832	198x	if (first_error)
833	1x	return first_error;
834	197x	return {};
835	198x	}
836
837		inline void
838	201x	posix_signal_service::cancel_wait(posix_signal& impl)
839		{
840	201x	bool was_waiting = false;
841	201x	signal_op* op = nullptr;
842
843		{
844	201x	std::lock_guard lock(mutex_);
845	201x	impl.cancelled_ = true;
846	201x	if (impl.waiting_)
847		{
848	7x	was_waiting = true;
849	7x	impl.waiting_ = false;
850	7x	op = &impl.pending_op_;
851		}
852	201x	}
853
854	201x	if (was_waiting)
855		{
856	7x	if (op->ec_out)
857	7x	*op->ec_out = make_error_code(capy::error::canceled);
858	7x	if (op->signal_out)
859	7x	*op->signal_out = 0;
860	7x	op->cont.h = op->h;
861	7x	op->d.post(op->cont);
862	7x	sched_->work_finished();
863		}
864	201x	}
865
866		inline void
867	651x	posix_signal_service::cancel_wait_token(posix_signal& impl) noexcept
868		{
869	651x	bool was_waiting = false;
870	651x	signal_op* op = nullptr;
871
872		{
873	651x	std::lock_guard lock(mutex_);
874		// Persist the request even when no wait is parked yet: wait()
875		// arms the callback before start_wait takes this lock, and
876		// start_wait consumes this flag.
877	651x	impl.token_cancelled_ = true;
878	651x	if (impl.waiting_)
879		{
880	514x	was_waiting = true;
881	514x	impl.waiting_ = false;
882	514x	op = &impl.pending_op_;
883		}
884	651x	}
885
886	651x	if (was_waiting)
887		{
888	514x	if (op->ec_out)
889	514x	*op->ec_out = make_error_code(capy::error::canceled);
890	514x	if (op->signal_out)
891	514x	*op->signal_out = 0;
892	514x	op->cont.h = op->h;
893	514x	op->d.post(op->cont);
894	514x	sched_->work_finished();
895		}
896	651x	}
897
898		inline void
899	651x	posix_signal::token_canceller::operator()() const noexcept
900		{
901	651x	self->svc_.cancel_wait_token(*self);
902	651x	}
903
904		inline void
905	985x	posix_signal_service::start_wait(posix_signal& impl, signal_op* op)
906		{
907		{
908	985x	std::lock_guard lock(mutex_);
909
910		// Check if cancel() was called before this wait started
911	985x	if (impl.cancelled_)
912		{
913	2x	impl.cancelled_ = false;
914	2x	if (op->ec_out)
915	2x	*op->ec_out = make_error_code(capy::error::canceled);
916	2x	if (op->signal_out)
917	2x	*op->signal_out = 0;
918	2x	op->cont.h = op->h;
919	2x	op->d.post(op->cont);
920	2x	return;
921		}
922
923		// A stop request that arrived between wait() arming the callback
924		// and this lock: complete now rather than parking forever.
925	983x	if (impl.token_cancelled_)
926		{
927	135x	impl.token_cancelled_ = false;
928	135x	if (op->ec_out)
929	135x	*op->ec_out = make_error_code(capy::error::canceled);
930	135x	if (op->signal_out)
931	135x	*op->signal_out = 0;
932	135x	op->cont.h = op->h;
933	135x	op->d.post(op->cont);
934	135x	return;
935		}
936
937		// Check for queued signals first (signal arrived before wait started)
938	848x	signal_registration* reg = impl.signals_;
939	1698x	while (reg)
940		{
941	852x	if (reg->undelivered > 0)
942		{
943	2x	--reg->undelivered;
944	2x	op->signal_number = reg->signal_number;
945		// svc=nullptr: no work_finished needed since we never called work_started
946	2x	op->svc = nullptr;
947	2x	sched_->post(op);
948	2x	return;
949		}
950	850x	reg = reg->next_in_set;
951		}
952
953		// No queued signals - wait for delivery
954	846x	impl.waiting_ = true;
955		// svc=this: signal_op::operator() will call work_finished() to balance this
956	846x	op->svc = this;
957	846x	sched_->work_started();
958	985x	}
959		}
960
961		inline void
962	317x	posix_signal_service::deliver_signal(int signal_number)
963		{
964	317x	if (signal_number < 0 \|\| signal_number >= max_signal_number)
965	✗	return;
966
967		posix_signal_detail::signal_state* state =
968	317x	posix_signal_detail::get_signal_state();
969	317x	std::lock_guard lock(state->mutex);
970
971	317x	posix_signal_service* service = state->service_list;
972	634x	while (service)
973		{
974	317x	std::lock_guard svc_lock(service->mutex_);
975
976	317x	signal_registration* reg = service->registrations_[signal_number];
977	638x	while (reg)
978		{
979	321x	posix_signal* impl = static_cast<posix_signal*>(reg->owner);
980
981	321x	if (impl->waiting_)
982		{
983	319x	impl->waiting_ = false;
984	319x	impl->pending_op_.signal_number = signal_number;
985	319x	service->post(&impl->pending_op_);
986		}
987		else
988		{
989	2x	++reg->undelivered;
990		}
991
992	321x	reg = reg->next_in_table;
993		}
994
995	317x	service = service->next_;
996	317x	}
997	317x	}
998
999		inline void
1000		posix_signal_service::work_started() noexcept
1001		{
1002		sched_->work_started();
1003		}
1004
1005		inline void
1006	319x	posix_signal_service::work_finished() noexcept
1007		{
1008	319x	sched_->work_finished();
1009	319x	}
1010
1011		inline void
1012	319x	posix_signal_service::post(signal_op* op)
1013		{
1014	319x	sched_->post(op);
1015	319x	}
1016
1017		inline void
1018	2241x	posix_signal_service::add_service(posix_signal_service* service)
1019		{
1020		posix_signal_detail::signal_state* state =
1021	2241x	posix_signal_detail::get_signal_state();
1022	2241x	std::lock_guard lock(state->mutex);
1023
1024	2241x	service->next_ = state->service_list;
1025	2241x	service->prev_ = nullptr;
1026	2241x	if (state->service_list)
1027	11x	state->service_list->prev_ = service;
1028	2241x	state->service_list = service;
1029	2241x	}
1030
1031		inline void
1032	2241x	posix_signal_service::remove_service(posix_signal_service* service)
1033		{
1034		posix_signal_detail::signal_state* state =
1035	2241x	posix_signal_detail::get_signal_state();
1036	2241x	std::lock_guard lock(state->mutex);
1037
1038	2241x	if (service->next_ \|\| service->prev_ \|\| state->service_list == service)
1039		{
1040	2241x	if (state->service_list == service)
1041	2239x	state->service_list = service->next_;
1042	2241x	if (service->prev_)
1043	2x	service->prev_->next_ = service->next_;
1044	2241x	if (service->next_)
1045	9x	service->next_->prev_ = service->prev_;
1046	2241x	service->next_ = nullptr;
1047	2241x	service->prev_ = nullptr;
1048		}
1049	2241x	}
1050
1051		// get_signal_service - factory function
1052
1053		inline posix_signal_service&
1054	2241x	get_signal_service(capy::execution_context& ctx, scheduler& sched)
1055		{
1056	2241x	return ctx.make_service<posix_signal_service>(sched);
1057		}
1058
1059		} // namespace detail
1060		} // namespace boost::corosio
1061
1062		#endif // BOOST_COROSIO_POSIX
1063
1064		#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_SIGNAL_SERVICE_HPP
1065