. /include/boost/corosio /native /detail /select /select_scheduler.hpp
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1   // 1   //
2   // Copyright (c) 2026 Steve Gerbino 2   // Copyright (c) 2026 Steve Gerbino
3   // Copyright (c) 2026 Michael Vandeberg 3   // Copyright (c) 2026 Michael Vandeberg
4   // 4   //
5   // Distributed under the Boost Software License, Version 1.0. (See accompanying 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) 6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7   // 7   //
8   // Official repository: https://github.com/cppalliance/corosio 8   // Official repository: https://github.com/cppalliance/corosio
9   // 9   //
10   10  
11   #ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 11   #ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
12   #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 12   #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
13   13  
14   #include <boost/corosio/detail/platform.hpp> 14   #include <boost/corosio/detail/platform.hpp>
15   15  
16   #if BOOST_COROSIO_HAS_SELECT 16   #if BOOST_COROSIO_HAS_SELECT
17   17  
18   #include <boost/corosio/detail/config.hpp> 18   #include <boost/corosio/detail/config.hpp>
19   #include <boost/capy/ex/execution_context.hpp> 19   #include <boost/capy/ex/execution_context.hpp>
20   20  
21   #include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp> 21   #include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp>
22   #include <boost/corosio/native/detail/reactor/reactor_signal_pipe.hpp> 22   #include <boost/corosio/native/detail/reactor/reactor_signal_pipe.hpp>
23   23  
24   #include <boost/corosio/native/detail/select/select_traits.hpp> 24   #include <boost/corosio/native/detail/select/select_traits.hpp>
25   #include <boost/corosio/detail/timer_service.hpp> 25   #include <boost/corosio/detail/timer_service.hpp>
26   #include <boost/corosio/native/detail/make_err.hpp> 26   #include <boost/corosio/native/detail/make_err.hpp>
27   #include <boost/corosio/native/detail/posix/posix_resolver_service.hpp> 27   #include <boost/corosio/native/detail/posix/posix_resolver_service.hpp>
28   #include <boost/corosio/native/detail/posix/posix_signal_service.hpp> 28   #include <boost/corosio/native/detail/posix/posix_signal_service.hpp>
29   #include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp> 29   #include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp>
30   #include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp> 30   #include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp>
31   31  
32   #include <boost/corosio/detail/except.hpp> 32   #include <boost/corosio/detail/except.hpp>
33   33  
34   #include <sys/select.h> 34   #include <sys/select.h>
35   #include <unistd.h> 35   #include <unistd.h>
36   #include <errno.h> 36   #include <errno.h>
37   #include <fcntl.h> 37   #include <fcntl.h>
38   38  
39   #include <atomic> 39   #include <atomic>
40   #include <chrono> 40   #include <chrono>
41   #include <cstdint> 41   #include <cstdint>
42   #include <limits> 42   #include <limits>
43   #include <mutex> 43   #include <mutex>
44   #include <new> 44   #include <new>
45   #include <unordered_map> 45   #include <unordered_map>
46   46  
47   namespace boost::corosio::detail { 47   namespace boost::corosio::detail {
48   48  
49   struct select_op; 49   struct select_op;
50   50  
51   /** POSIX scheduler using select() for I/O multiplexing. 51   /** POSIX scheduler using select() for I/O multiplexing.
52   52  
53   This scheduler implements the scheduler interface using the POSIX select() 53   This scheduler implements the scheduler interface using the POSIX select()
54   call for I/O event notification. It inherits the shared reactor threading 54   call for I/O event notification. It inherits the shared reactor threading
55   model from reactor_scheduler: signal state machine, inline completion 55   model from reactor_scheduler: signal state machine, inline completion
56   budget, work counting, and the do_one event loop. 56   budget, work counting, and the do_one event loop.
57   57  
58   The design mirrors epoll_scheduler for behavioral consistency: 58   The design mirrors epoll_scheduler for behavioral consistency:
59   - Same single-reactor thread coordination model 59   - Same single-reactor thread coordination model
60   - Same deferred I/O pattern (reactor marks ready; workers do I/O) 60   - Same deferred I/O pattern (reactor marks ready; workers do I/O)
61   - Same timer integration pattern 61   - Same timer integration pattern
62   62  
63   Known Limitations: 63   Known Limitations:
64   - FD_SETSIZE (~1024) limits maximum concurrent connections 64   - FD_SETSIZE (~1024) limits maximum concurrent connections
65   - O(n) scanning: rebuilds fd_sets each iteration 65   - O(n) scanning: rebuilds fd_sets each iteration
66   - Level-triggered only (no edge-triggered mode) 66   - Level-triggered only (no edge-triggered mode)
67   67  
68   @par Thread Safety 68   @par Thread Safety
69   All public member functions are thread-safe. 69   All public member functions are thread-safe.
70   */ 70   */
71   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler 71   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler
72   { 72   {
73   public: 73   public:
74   /** Construct the scheduler. 74   /** Construct the scheduler.
75   75  
76   Creates a self-pipe for reactor interruption. 76   Creates a self-pipe for reactor interruption.
77   77  
78   @param ctx Reference to the owning execution_context. 78   @param ctx Reference to the owning execution_context.
79   @param concurrency_hint Hint for expected thread count (unused). 79   @param concurrency_hint Hint for expected thread count (unused).
80   */ 80   */
81   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1); 81   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
82   82  
83   /// Destroy the scheduler. 83   /// Destroy the scheduler.
84   ~select_scheduler() override; 84   ~select_scheduler() override;
85   85  
86   select_scheduler(select_scheduler const&) = delete; 86   select_scheduler(select_scheduler const&) = delete;
87   select_scheduler& operator=(select_scheduler const&) = delete; 87   select_scheduler& operator=(select_scheduler const&) = delete;
88   88  
89   /// Shut down the scheduler, draining pending operations. 89   /// Shut down the scheduler, draining pending operations.
90   void shutdown() override; 90   void shutdown() override;
91   91  
92   /** Return the maximum file descriptor value supported. 92   /** Return the maximum file descriptor value supported.
93   93  
94   Returns FD_SETSIZE - 1, the maximum fd value that can be 94   Returns FD_SETSIZE - 1, the maximum fd value that can be
95   monitored by select(). Operations with fd >= FD_SETSIZE 95   monitored by select(). Operations with fd >= FD_SETSIZE
96   will fail with EINVAL. 96   will fail with EINVAL.
97   97  
98   @return The maximum supported file descriptor value. 98   @return The maximum supported file descriptor value.
99   */ 99   */
100   static constexpr int max_fd() noexcept 100   static constexpr int max_fd() noexcept
101   { 101   {
102   return FD_SETSIZE - 1; 102   return FD_SETSIZE - 1;
103   } 103   }
104   104  
105   /** Register a descriptor for persistent monitoring. 105   /** Register a descriptor for persistent monitoring.
106   106  
107   The fd is added to the registered_descs_ map and will be 107   The fd is added to the registered_descs_ map and will be
108   included in subsequent select() calls. The reactor is 108   included in subsequent select() calls. The reactor is
109   interrupted so a blocked select() rebuilds its fd_sets. 109   interrupted so a blocked select() rebuilds its fd_sets.
110   110  
111   @param fd The file descriptor to register. 111   @param fd The file descriptor to register.
112   @param desc Pointer to descriptor state for this fd. 112   @param desc Pointer to descriptor state for this fd.
113   113  
114   @return The error if the fd cannot be tracked, otherwise a 114   @return The error if the fd cannot be tracked, otherwise a
115   default constructed error code. 115   default constructed error code.
116   */ 116   */
117   std::error_code 117   std::error_code
118   register_descriptor(int fd, reactor_descriptor_state* desc) const; 118   register_descriptor(int fd, reactor_descriptor_state* desc) const;
119   119  
120   /** Deregister a persistently registered descriptor. 120   /** Deregister a persistently registered descriptor.
121   121  
122   @param fd The file descriptor to deregister. 122   @param fd The file descriptor to deregister.
123   */ 123   */
124   void deregister_descriptor(int fd) const; 124   void deregister_descriptor(int fd) const;
125   125  
126   /** Interrupt the reactor so it rebuilds its fd_sets. 126   /** Interrupt the reactor so it rebuilds its fd_sets.
127   127  
128   Called when a write, connect, or write-wait op is registered 128   Called when a write, connect, or write-wait op is registered
129   after the reactor's snapshot was taken. Without this, 129   after the reactor's snapshot was taken. Without this,
130   select() may block not watching for writability on the fd. 130   select() may block not watching for writability on the fd.
131   */ 131   */
132   void notify_reactor() const; 132   void notify_reactor() const;
133   133  
134   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp). 134   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp).
HITCBC 135   55 [[nodiscard]] std::error_code register_signal_reader(int read_fd) override 135   55 [[nodiscard]] std::error_code register_signal_reader(int read_fd) override
136   { 136   {
HITCBC 137   55 return register_descriptor(read_fd, signal_pipe_reader_.arm()); 137   55 return register_descriptor(read_fd, signal_pipe_reader_.arm());
138   } 138   }
139   139  
140   private: 140   private:
141   void run_task(lock_type& lock, context_type& ctx, long timeout_us) override; 141   void run_task(lock_type& lock, context_type& ctx, long timeout_us) override;
142   void interrupt_reactor() const override; 142   void interrupt_reactor() const override;
143   long calculate_timeout(long requested_timeout_us) const; 143   long calculate_timeout(long requested_timeout_us) const;
144   144  
145   // Watches the global signal self-pipe's read end (armed lazily by 145   // Watches the global signal self-pipe's read end (armed lazily by
146   // register_signal_reader on the first signal registration). 146   // register_signal_reader on the first signal registration).
147   reactor_signal_pipe_reader signal_pipe_reader_; 147   reactor_signal_pipe_reader signal_pipe_reader_;
148   148  
149   // Self-pipe for interrupting select() 149   // Self-pipe for interrupting select()
150   int pipe_fds_[2]; // [0]=read, [1]=write 150   int pipe_fds_[2]; // [0]=read, [1]=write
151   151  
152   // Per-fd tracking for fd_set building 152   // Per-fd tracking for fd_set building
153   mutable std::unordered_map<int, reactor_descriptor_state*> 153   mutable std::unordered_map<int, reactor_descriptor_state*>
154   registered_descs_; 154   registered_descs_;
155   mutable int max_fd_ = -1; 155   mutable int max_fd_ = -1;
156   }; 156   };
157   157  
HITCBC 158   886 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int) 158   886 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 159   886 : pipe_fds_{-1, -1} 159   886 : pipe_fds_{-1, -1}
HITCBC 160   886 , max_fd_(-1) 160   886 , max_fd_(-1)
161   { 161   {
HITCBC 162   886 if (::pipe(pipe_fds_) < 0) 162   886 if (::pipe(pipe_fds_) < 0)
HITCBC 163   1 detail::throw_system_error(make_err(errno), "pipe"); 163   1 detail::throw_system_error(make_err(errno), "pipe");
164   164  
HITCBC 165   2646 for (int i = 0; i < 2; ++i) 165   2646 for (int i = 0; i < 2; ++i)
166   { 166   {
HITCBC 167   1767 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 167   1767 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 168   1767 if (flags == -1) 168   1767 if (flags == -1)
169   { 169   {
HITCBC 170   2 int errn = errno; 170   2 int errn = errno;
HITCBC 171   2 ::close(pipe_fds_[0]); 171   2 ::close(pipe_fds_[0]);
HITCBC 172   2 ::close(pipe_fds_[1]); 172   2 ::close(pipe_fds_[1]);
HITCBC 173   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL"); 173   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
174   } 174   }
HITCBC 175   1765 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 175   1765 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
176   { 176   {
HITCBC 177   2 int errn = errno; 177   2 int errn = errno;
HITCBC 178   2 ::close(pipe_fds_[0]); 178   2 ::close(pipe_fds_[0]);
HITCBC 179   2 ::close(pipe_fds_[1]); 179   2 ::close(pipe_fds_[1]);
HITCBC 180   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL"); 180   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
181   } 181   }
HITCBC 182   1763 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 182   1763 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
183   { 183   {
HITCBC 184   2 int errn = errno; 184   2 int errn = errno;
HITCBC 185   2 ::close(pipe_fds_[0]); 185   2 ::close(pipe_fds_[0]);
HITCBC 186   2 ::close(pipe_fds_[1]); 186   2 ::close(pipe_fds_[1]);
HITCBC 187   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD"); 187   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
188   } 188   }
189   } 189   }
190   190  
HITCBC 191   879 timer_svc_ = &get_timer_service(ctx, *this); 191   879 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 192   879 timer_svc_->set_on_earliest_changed( 192   879 timer_svc_->set_on_earliest_changed(
HITCBC 193   3597 timer_service::callback(this, [](void* p) { 193   3436 timer_service::callback(this, [](void* p) {
HITCBC 194   2718 static_cast<select_scheduler*>(p)->interrupt_reactor(); 194   2557 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 195   2718 })); 195   2557 }));
196   196  
HITCBC 197   879 get_resolver_service(ctx, *this); 197   879 get_resolver_service(ctx, *this);
HITCBC 198   879 get_signal_service(ctx, *this); 198   879 get_signal_service(ctx, *this);
HITCBC 199   879 get_stream_file_service(ctx, *this); 199   879 get_stream_file_service(ctx, *this);
HITCBC 200   879 get_random_access_file_service(ctx, *this); 200   879 get_random_access_file_service(ctx, *this);
201   201  
HITCBC 202   879 completed_ops_.push(&task_op_); 202   879 completed_ops_.push(&task_op_);
HITCBC 203   900 } 203   900 }
204   204  
HITCBC 205   1758 inline select_scheduler::~select_scheduler() 205   1758 inline select_scheduler::~select_scheduler()
206   { 206   {
HITCBC 207   879 if (pipe_fds_[0] >= 0) 207   879 if (pipe_fds_[0] >= 0)
HITCBC 208   879 ::close(pipe_fds_[0]); 208   879 ::close(pipe_fds_[0]);
HITCBC 209   879 if (pipe_fds_[1] >= 0) 209   879 if (pipe_fds_[1] >= 0)
HITCBC 210   879 ::close(pipe_fds_[1]); 210   879 ::close(pipe_fds_[1]);
HITCBC 211   1758 } 211   1758 }
212   212  
213   inline void 213   inline void
HITCBC 214   879 select_scheduler::shutdown() 214   879 select_scheduler::shutdown()
215   { 215   {
HITCBC 216   879 shutdown_drain(); 216   879 shutdown_drain();
217   217  
HITCBC 218   879 if (pipe_fds_[1] >= 0) 218   879 if (pipe_fds_[1] >= 0)
HITCBC 219   879 interrupt_reactor(); 219   879 interrupt_reactor();
HITCBC 220   879 } 220   879 }
221   221  
222   inline std::error_code 222   inline std::error_code
HITCBC 223   4822 select_scheduler::register_descriptor( 223   4842 select_scheduler::register_descriptor(
224   int fd, reactor_descriptor_state* desc) const 224   int fd, reactor_descriptor_state* desc) const
225   { 225   {
HITCBC 226   4822 if (fd < 0 || fd >= FD_SETSIZE) 226   4842 if (fd < 0 || fd >= FD_SETSIZE)
HITCBC 227   1 return make_err(EMFILE); 227   1 return make_err(EMFILE);
228   228  
HITCBC 229   4821 desc->registered_events = reactor_event_read | reactor_event_write; 229   4841 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 230   4821 desc->fd = fd; 230   4841 desc->fd = fd;
HITCBC 231   4821 desc->scheduler_ = this; 231   4841 desc->scheduler_ = this;
HITCBC 232   4821 desc->mutex.set_enabled(reactor_io_locking_); 232   4841 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 233   4821 desc->ready_events_.store(0, std::memory_order_relaxed); 233   4841 desc->ready_events_.store(0, std::memory_order_relaxed);
234   234  
235   { 235   {
HITCBC 236   4821 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 236   4841 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 237   4821 desc->impl_ref_.reset(); 237   4841 desc->impl_ref_.reset();
HITCBC 238   4821 desc->read_ready = false; 238   4841 desc->read_ready = false;
HITCBC 239   4821 desc->write_ready = false; 239   4841 desc->write_ready = false;
HITCBC 240   4821 } 240   4841 }
241   241  
242   { 242   {
HITCBC 243   4821 mutex_type::scoped_lock lock(mutex_); 243   4841 mutex_type::scoped_lock lock(mutex_);
244   try 244   try
245   { 245   {
HITCBC 246   4821 registered_descs_[fd] = desc; 246   4841 registered_descs_[fd] = desc;
247   } 247   }
HITCBC 248   1 catch (std::bad_alloc const&) 248   1 catch (std::bad_alloc const&)
249   { 249   {
HITCBC 250   1 return make_err(ENOMEM); 250   1 return make_err(ENOMEM);
HITCBC 251   1 } 251   1 }
HITCBC 252   4820 if (fd > max_fd_) 252   4840 if (fd > max_fd_)
HITCBC 253   4766 max_fd_ = fd; 253   4786 max_fd_ = fd;
HITCBC 254   4821 } 254   4841 }
255   255  
HITCBC 256   4820 interrupt_reactor(); 256   4840 interrupt_reactor();
HITCBC 257   4820 return {}; 257   4840 return {};
258   } 258   }
259   259  
260   inline void 260   inline void
HITCBC 261   4766 select_scheduler::deregister_descriptor(int fd) const 261   4786 select_scheduler::deregister_descriptor(int fd) const
262   { 262   {
HITCBC 263   4766 mutex_type::scoped_lock lock(mutex_); 263   4786 mutex_type::scoped_lock lock(mutex_);
264   264  
HITCBC 265   4766 auto it = registered_descs_.find(fd); 265   4786 auto it = registered_descs_.find(fd);
HITCBC 266   4766 if (it == registered_descs_.end()) 266   4786 if (it == registered_descs_.end())
MISUBC 267   ✗ return; 267   ✗ return;
268   268  
HITCBC 269   4766 registered_descs_.erase(it); 269   4786 registered_descs_.erase(it);
270   270  
HITCBC 271   4766 if (fd == max_fd_) 271   4786 if (fd == max_fd_)
272   { 272   {
HITCBC 273   4429 max_fd_ = pipe_fds_[0]; 273   4449 max_fd_ = pipe_fds_[0];
HITCBC 274   8456 for (auto& [registered_fd, state] : registered_descs_) 274   8496 for (auto& [registered_fd, state] : registered_descs_)
275   { 275   {
HITCBC 276   4027 if (registered_fd > max_fd_) 276   4047 if (registered_fd > max_fd_)
HITCBC 277   3934 max_fd_ = registered_fd; 277   3954 max_fd_ = registered_fd;
278   } 278   }
279   } 279   }
HITCBC 280   4766 } 280   4786 }
281   281  
282   inline void 282   inline void
HITCBC 283   2143 select_scheduler::notify_reactor() const 283   2153 select_scheduler::notify_reactor() const
284   { 284   {
HITCBC 285   2143 interrupt_reactor(); 285   2153 interrupt_reactor();
HITCBC 286   2143 } 286   2153 }
287   287  
288   inline void 288   inline void
HITCBC 289   11363 select_scheduler::interrupt_reactor() const 289   11223 select_scheduler::interrupt_reactor() const
290   { 290   {
HITCBC 291   11363 char byte = 1; 291   11223 char byte = 1;
HITCBC 292   11363 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 292   11223 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 293   11363 } 293   11223 }
294   294  
295   inline long 295   inline long
HITCBC 296   281696 select_scheduler::calculate_timeout(long requested_timeout_us) const 296   292405 select_scheduler::calculate_timeout(long requested_timeout_us) const
297   { 297   {
HITCBC 298   281696 if (requested_timeout_us == 0) 298   292405 if (requested_timeout_us == 0)
299   return 0; // LCOV_EXCL_LINE run_task passes 0 via task_interrupted_, never through this argument 299   return 0; // LCOV_EXCL_LINE run_task passes 0 via task_interrupted_, never through this argument
300   300  
HITCBC 301   281696 auto nearest = timer_svc_->nearest_expiry(); 301   292405 auto nearest = timer_svc_->nearest_expiry();
HITCBC 302   281696 if (nearest == timer_service::time_point::max()) 302   292405 if (nearest == timer_service::time_point::max())
HITCBC 303   736 return requested_timeout_us; 303   726 return requested_timeout_us;
304   304  
HITCBC 305   280960 auto now = std::chrono::steady_clock::now(); 305   291679 auto now = std::chrono::steady_clock::now();
HITCBC 306   280960 if (nearest <= now) 306   291679 if (nearest <= now)
HITCBC 307   665 return 0; 307   691 return 0;
308   308  
309   auto timer_timeout_us = 309   auto timer_timeout_us =
HITCBC 310   280295 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 310   290988 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 311   280295 .count(); 311   290988 .count();
312   312  
HITCBC 313   280295 constexpr auto long_max = 313   290988 constexpr auto long_max =
314   static_cast<long long>((std::numeric_limits<long>::max)()); 314   static_cast<long long>((std::numeric_limits<long>::max)());
315   auto capped_timer_us = 315   auto capped_timer_us =
HITCBC 316   280295 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 316   290988 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 317   280295 static_cast<long long>(0)), 317   290988 static_cast<long long>(0)),
HITCBC 318   280295 long_max); 318   290988 long_max);
319   319  
HITCBC 320   280295 if (requested_timeout_us < 0) 320   290988 if (requested_timeout_us < 0)
HITCBC 321   280293 return static_cast<long>(capped_timer_us); 321   290986 return static_cast<long>(capped_timer_us);
322   322  
323   return static_cast<long>( 323   return static_cast<long>(
HITCBC 324   2 (std::min)(static_cast<long long>(requested_timeout_us), 324   2 (std::min)(static_cast<long long>(requested_timeout_us),
HITCBC 325   2 capped_timer_us)); 325   2 capped_timer_us));
326   } 326   }
327   327  
328   inline void 328   inline void
HITCBC 329   306444 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us) 329   315456 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us)
330   { 330   {
331   long effective_timeout_us = 331   long effective_timeout_us =
HITCBC 332   306444 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 332   315456 task_interrupted_ ? 0 : calculate_timeout(timeout_us);
333   333  
334   // Snapshot registered descriptors while holding lock. 334   // Snapshot registered descriptors while holding lock.
335   // Record which fds need write monitoring to avoid a hot loop: 335   // Record which fds need write monitoring to avoid a hot loop:
336   // select is level-triggered so writable sockets (nearly always 336   // select is level-triggered so writable sockets (nearly always
337   // writable) would cause select() to return immediately every 337   // writable) would cause select() to return immediately every
338   // iteration if unconditionally added to write_fds. Membership 338   // iteration if unconditionally added to write_fds. Membership
339   // stays opt-in: a parked write wait opts in the same way a 339   // stays opt-in: a parked write wait opts in the same way a
340   // parked write or connect op does. 340   // parked write or connect op does.
341   struct fd_entry 341   struct fd_entry
342   { 342   {
343   int fd; 343   int fd;
344   reactor_descriptor_state* desc; 344   reactor_descriptor_state* desc;
345   bool needs_write; 345   bool needs_write;
346   }; 346   };
347   fd_entry snapshot[FD_SETSIZE]; 347   fd_entry snapshot[FD_SETSIZE];
HITCBC 348   306444 int snapshot_count = 0; 348   315456 int snapshot_count = 0;
349   349  
HITCBC 350   798730 for (auto& [fd, desc] : registered_descs_) 350   816306 for (auto& [fd, desc] : registered_descs_)
351   { 351   {
HITCBC 352   492286 if (snapshot_count < FD_SETSIZE) 352   500850 if (snapshot_count < FD_SETSIZE)
353   { 353   {
HITCBC 354   492286 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 354   500850 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 355   492286 snapshot[snapshot_count].fd = fd; 355   500850 snapshot[snapshot_count].fd = fd;
HITCBC 356   492286 snapshot[snapshot_count].desc = desc; 356   500850 snapshot[snapshot_count].desc = desc;
HITCBC 357   492286 snapshot[snapshot_count].needs_write = 357   500850 snapshot[snapshot_count].needs_write =
HITCBC 358   492286 (desc->write_op || desc->connect_op || desc->wait_write_op); 358   500850 (desc->write_op || desc->connect_op || desc->wait_write_op);
HITCBC 359   492286 ++snapshot_count; 359   500850 ++snapshot_count;
HITCBC 360   492286 } 360   500850 }
361   } 361   }
362   362  
HITCBC 363   306444 if (lock.owns_lock()) 363   315456 if (lock.owns_lock())
HITCBC 364   281697 lock.unlock(); 364   292406 lock.unlock();
365   365  
HITCBC 366   306444 task_cleanup on_exit{this, &lock, ctx}; 366   315456 task_cleanup on_exit{this, &lock, ctx};
367   367  
368   fd_set read_fds, write_fds, except_fds; 368   fd_set read_fds, write_fds, except_fds;
HITCBC 369   5209548 FD_ZERO(&read_fds); 369   5362752 FD_ZERO(&read_fds);
HITCBC 370   5209548 FD_ZERO(&write_fds); 370   5362752 FD_ZERO(&write_fds);
HITCBC 371   5209548 FD_ZERO(&except_fds); 371   5362752 FD_ZERO(&except_fds);
372   372  
HITCBC 373   306444 FD_SET(pipe_fds_[0], &read_fds); 373   315456 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 374   306444 int nfds = pipe_fds_[0]; 374   315456 int nfds = pipe_fds_[0];
375   375  
HITCBC 376   798730 for (int i = 0; i < snapshot_count; ++i) 376   816306 for (int i = 0; i < snapshot_count; ++i)
377   { 377   {
HITCBC 378   492286 int fd = snapshot[i].fd; 378   500850 int fd = snapshot[i].fd;
HITCBC 379   492286 FD_SET(fd, &read_fds); 379   500850 FD_SET(fd, &read_fds);
HITCBC 380   492286 if (snapshot[i].needs_write) 380   500850 if (snapshot[i].needs_write)
HITCBC 381   13123 FD_SET(fd, &write_fds); 381   12815 FD_SET(fd, &write_fds);
HITCBC 382   492286 FD_SET(fd, &except_fds); 382   500850 FD_SET(fd, &except_fds);
HITCBC 383   492286 if (fd > nfds) 383   500850 if (fd > nfds)
HITCBC 384   306055 nfds = fd; 384   315058 nfds = fd;
385   } 385   }
386   386  
387   struct timeval tv; 387   struct timeval tv;
HITCBC 388   306444 struct timeval* tv_ptr = nullptr; 388   315456 struct timeval* tv_ptr = nullptr;
HITCBC 389   306444 if (effective_timeout_us >= 0) 389   315456 if (effective_timeout_us >= 0)
390   { 390   {
HITCBC 391   305724 tv.tv_sec = effective_timeout_us / 1000000; 391   314747 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 392   305724 tv.tv_usec = effective_timeout_us % 1000000; 392   314747 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 393   305724 tv_ptr = &tv; 393   314747 tv_ptr = &tv;
394   } 394   }
395   395  
HITCBC 396   306444 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 396   315456 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
397   397  
398   // EINTR: signal interrupted select(), just retry. 398   // EINTR: signal interrupted select(), just retry.
399   // EBADF: an fd was closed between snapshot and select(); retry 399   // EBADF: an fd was closed between snapshot and select(); retry
400   // with a fresh snapshot from registered_descs_. 400   // with a fresh snapshot from registered_descs_.
401   // Both fall through with no ready descriptors rather than 401   // Both fall through with no ready descriptors rather than
402   // returning: the caller handed this function an owned lock that 402   // returning: the caller handed this function an owned lock that
403   // only the epilogue below re-acquires. 403   // only the epilogue below re-acquires.
HITCBC 404   306444 if (ready < 0) 404   315456 if (ready < 0)
405   { 405   {
HITCBC 406   3 if (errno != EINTR && errno != EBADF) 406   3 if (errno != EINTR && errno != EBADF)
HITCBC 407   1 detail::throw_system_error(make_err(errno), "select"); 407   1 detail::throw_system_error(make_err(errno), "select");
HITCBC 408   2 ready = 0; 408   2 ready = 0;
409   } 409   }
410   410  
411   // Process timers outside the lock 411   // Process timers outside the lock
HITCBC 412   306443 timer_svc_->process_expired(); 412   315455 timer_svc_->process_expired();
413   413  
HITCBC 414   306443 ready_queue local_ops; 414   315455 ready_queue local_ops;
415   415  
HITCBC 416   306443 if (ready > 0) 416   315455 if (ready > 0)
417   { 417   {
HITCBC 418   289596 if (FD_ISSET(pipe_fds_[0], &read_fds)) 418   299643 if (FD_ISSET(pipe_fds_[0], &read_fds))
419   { 419   {
420   char buf[256]; 420   char buf[256];
HITCBC 421   9980 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 421   10006 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
422   { 422   {
423   } 423   }
424   } 424   }
425   425  
HITCBC 426   730163 for (int i = 0; i < snapshot_count; ++i) 426   753259 for (int i = 0; i < snapshot_count; ++i)
427   { 427   {
HITCBC 428   440567 int fd = snapshot[i].fd; 428   453616 int fd = snapshot[i].fd;
HITCBC 429   440567 reactor_descriptor_state* desc = snapshot[i].desc; 429   453616 reactor_descriptor_state* desc = snapshot[i].desc;
430   430  
HITCBC 431   440567 std::uint32_t flags = 0; 431   453616 std::uint32_t flags = 0;
HITCBC 432   440567 if (FD_ISSET(fd, &read_fds)) 432   453616 if (FD_ISSET(fd, &read_fds))
HITCBC 433   289203 flags |= reactor_event_read; 433   299329 flags |= reactor_event_read;
HITCBC 434   440567 if (FD_ISSET(fd, &write_fds)) 434   453616 if (FD_ISSET(fd, &write_fds))
HITCBC 435   2135 flags |= reactor_event_write; 435   2145 flags |= reactor_event_write;
HITCBC 436   440567 if (FD_ISSET(fd, &except_fds)) 436   453616 if (FD_ISSET(fd, &except_fds))
HITCBC 437   16 flags |= reactor_event_error; 437   16 flags |= reactor_event_error;
438   438  
HITCBC 439   440567 if (flags == 0) 439   453616 if (flags == 0)
HITCBC 440   149238 continue; 440   152151 continue;
441   441  
HITCBC 442   291329 desc->add_ready_events(flags); 442   301465 desc->add_ready_events(flags);
443   443  
HITCBC 444   291329 bool expected = false; 444   301465 bool expected = false;
HITCBC 445   291329 if (desc->is_enqueued_.compare_exchange_strong( 445   301465 if (desc->is_enqueued_.compare_exchange_strong(
446   expected, true, std::memory_order_release, 446   expected, true, std::memory_order_release,
447   std::memory_order_relaxed)) 447   std::memory_order_relaxed))
448   { 448   {
HITCBC 449   291329 local_ops.push(desc); 449   301465 local_ops.push(desc);
450   } 450   }
451   } 451   }
452   } 452   }
453   453  
HITCBC 454   306443 lock.lock(); 454   315455 lock.lock();
455   455  
HITCBC 456   306443 completed_ops_.splice(local_ops); 456   315455 completed_ops_.splice(local_ops);
HITCBC 457   306444 } 457   315456 }
458   458  
459   } // namespace boost::corosio::detail 459   } // namespace boost::corosio::detail
460   460  
461   #endif // BOOST_COROSIO_HAS_SELECT 461   #endif // BOOST_COROSIO_HAS_SELECT
462   462  
463   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 463   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP