. /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).
135   [[nodiscard]] std::error_code 135   [[nodiscard]] std::error_code
HITCBC 136   47 register_signal_reader(int read_fd) override 136   55 register_signal_reader(int read_fd) override
137   { 137   {
HITCBC 138   47 return register_descriptor(read_fd, signal_pipe_reader_.arm()); 138   55 return register_descriptor(read_fd, signal_pipe_reader_.arm());
139   } 139   }
140   140  
141   private: 141   private:
142   void 142   void
143 - run_task(lock_type& lock, context_type* ctx, 143 + run_task(lock_type& lock, context_type& ctx,
144   long timeout_us) override; 144   long timeout_us) override;
145   void interrupt_reactor() const override; 145   void interrupt_reactor() const override;
146   long calculate_timeout(long requested_timeout_us) const; 146   long calculate_timeout(long requested_timeout_us) const;
147   147  
148   // Watches the global signal self-pipe's read end (armed lazily by 148   // Watches the global signal self-pipe's read end (armed lazily by
149   // register_signal_reader on the first signal registration). 149   // register_signal_reader on the first signal registration).
150   reactor_signal_pipe_reader signal_pipe_reader_; 150   reactor_signal_pipe_reader signal_pipe_reader_;
151   151  
152   // Self-pipe for interrupting select() 152   // Self-pipe for interrupting select()
153   int pipe_fds_[2]; // [0]=read, [1]=write 153   int pipe_fds_[2]; // [0]=read, [1]=write
154   154  
155   // Per-fd tracking for fd_set building 155   // Per-fd tracking for fd_set building
156   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_; 156   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_;
157   mutable int max_fd_ = -1; 157   mutable int max_fd_ = -1;
158   }; 158   };
159   159  
HITCBC 160   788 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int) 160   881 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 161   788 : pipe_fds_{-1, -1} 161   881 : pipe_fds_{-1, -1}
HITCBC 162   788 , max_fd_(-1) 162   881 , max_fd_(-1)
163   { 163   {
HITCBC 164   788 if (::pipe(pipe_fds_) < 0) 164   881 if (::pipe(pipe_fds_) < 0)
HITCBC 165   1 detail::throw_system_error(make_err(errno), "pipe"); 165   1 detail::throw_system_error(make_err(errno), "pipe");
166   166  
HITCBC 167   2352 for (int i = 0; i < 2; ++i) 167   2631 for (int i = 0; i < 2; ++i)
168   { 168   {
HITCBC 169   1571 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 169   1757 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 170   1571 if (flags == -1) 170   1757 if (flags == -1)
171   { 171   {
HITCBC 172   2 int errn = errno; 172   2 int errn = errno;
HITCBC 173   2 ::close(pipe_fds_[0]); 173   2 ::close(pipe_fds_[0]);
HITCBC 174   2 ::close(pipe_fds_[1]); 174   2 ::close(pipe_fds_[1]);
HITCBC 175   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL"); 175   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
176   } 176   }
HITCBC 177   1569 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 177   1755 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
178   { 178   {
HITCBC 179   2 int errn = errno; 179   2 int errn = errno;
HITCBC 180   2 ::close(pipe_fds_[0]); 180   2 ::close(pipe_fds_[0]);
HITCBC 181   2 ::close(pipe_fds_[1]); 181   2 ::close(pipe_fds_[1]);
HITCBC 182   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL"); 182   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
183   } 183   }
HITCBC 184   1567 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 184   1753 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
185   { 185   {
HITCBC 186   2 int errn = errno; 186   2 int errn = errno;
HITCBC 187   2 ::close(pipe_fds_[0]); 187   2 ::close(pipe_fds_[0]);
HITCBC 188   2 ::close(pipe_fds_[1]); 188   2 ::close(pipe_fds_[1]);
HITCBC 189   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD"); 189   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
190   } 190   }
191   } 191   }
192   192  
HITCBC 193   781 timer_svc_ = &get_timer_service(ctx, *this); 193   874 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 194   781 timer_svc_->set_on_earliest_changed( 194   874 timer_svc_->set_on_earliest_changed(
HITCBC 195   4630 timer_service::callback(this, [](void* p) { 195   3714 timer_service::callback(this, [](void* p) {
HITCBC 196   3849 static_cast<select_scheduler*>(p)->interrupt_reactor(); 196   2840 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 197   3849 })); 197   2840 }));
198   198  
HITCBC 199   781 get_resolver_service(ctx, *this); 199   874 get_resolver_service(ctx, *this);
HITCBC 200   781 get_signal_service(ctx, *this); 200   874 get_signal_service(ctx, *this);
HITCBC 201   781 get_stream_file_service(ctx, *this); 201   874 get_stream_file_service(ctx, *this);
HITCBC 202   781 get_random_access_file_service(ctx, *this); 202   874 get_random_access_file_service(ctx, *this);
203   203  
HITCBC 204   781 completed_ops_.push(&task_op_); 204   874 completed_ops_.push(&task_op_);
HITCBC 205   802 } 205   895 }
206   206  
HITCBC 207   1562 inline select_scheduler::~select_scheduler() 207   1748 inline select_scheduler::~select_scheduler()
208   { 208   {
HITCBC 209   781 if (pipe_fds_[0] >= 0) 209   874 if (pipe_fds_[0] >= 0)
HITCBC 210   781 ::close(pipe_fds_[0]); 210   874 ::close(pipe_fds_[0]);
HITCBC 211   781 if (pipe_fds_[1] >= 0) 211   874 if (pipe_fds_[1] >= 0)
HITCBC 212   781 ::close(pipe_fds_[1]); 212   874 ::close(pipe_fds_[1]);
HITCBC 213   1562 } 213   1748 }
214   214  
215   inline void 215   inline void
HITCBC 216   781 select_scheduler::shutdown() 216   874 select_scheduler::shutdown()
217   { 217   {
HITCBC 218   781 shutdown_drain(); 218   874 shutdown_drain();
219   219  
HITCBC 220   781 if (pipe_fds_[1] >= 0) 220   874 if (pipe_fds_[1] >= 0)
HITCBC 221   781 interrupt_reactor(); 221   874 interrupt_reactor();
HITCBC 222   781 } 222   874 }
223   223  
224   inline std::error_code 224   inline std::error_code
HITCBC 225   6861 select_scheduler::register_descriptor( 225   5234 select_scheduler::register_descriptor(
226   int fd, reactor_descriptor_state* desc) const 226   int fd, reactor_descriptor_state* desc) const
227   { 227   {
HITCBC 228   6861 if (fd < 0 || fd >= FD_SETSIZE) 228   5234 if (fd < 0 || fd >= FD_SETSIZE)
HITCBC 229   1 return make_err(EMFILE); 229   1 return make_err(EMFILE);
230   230  
HITCBC 231   6860 desc->registered_events = reactor_event_read | reactor_event_write; 231   5233 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 232   6860 desc->fd = fd; 232   5233 desc->fd = fd;
HITCBC 233   6860 desc->scheduler_ = this; 233   5233 desc->scheduler_ = this;
HITCBC 234   6860 desc->mutex.set_enabled(reactor_io_locking_); 234   5233 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 235   6860 desc->ready_events_.store(0, std::memory_order_relaxed); 235   5233 desc->ready_events_.store(0, std::memory_order_relaxed);
236   236  
237   { 237   {
HITCBC 238   6860 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 238   5233 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 239   6860 desc->impl_ref_.reset(); 239   5233 desc->impl_ref_.reset();
HITCBC 240   6860 desc->read_ready = false; 240   5233 desc->read_ready = false;
HITCBC 241   6860 desc->write_ready = false; 241   5233 desc->write_ready = false;
HITCBC 242   6860 } 242   5233 }
243   243  
244   { 244   {
HITCBC 245   6860 mutex_type::scoped_lock lock(mutex_); 245   5233 mutex_type::scoped_lock lock(mutex_);
246   try 246   try
247   { 247   {
HITCBC 248   6860 registered_descs_[fd] = desc; 248   5233 registered_descs_[fd] = desc;
249   } 249   }
HITGBC 250   ✗ catch (std::bad_alloc const&) 250   1 catch (std::bad_alloc const&)
251   { 251   {
HITGBC 252   ✗ return make_err(ENOMEM); 252   1 return make_err(ENOMEM);
HITGBC 253   ✗ } 253   1 }
HITCBC 254   6860 if (fd > max_fd_) 254   5232 if (fd > max_fd_)
HITCBC 255   6845 max_fd_ = fd; 255   5178 max_fd_ = fd;
HITCBC 256   6860 } 256   5233 }
257   257  
HITCBC 258   6860 interrupt_reactor(); 258   5232 interrupt_reactor();
HITCBC 259   6860 return {}; 259   5232 return {};
260   } 260   }
261   261  
262   inline void 262   inline void
HITCBC 263   6814 select_scheduler::deregister_descriptor(int fd) const 263   5178 select_scheduler::deregister_descriptor(int fd) const
264   { 264   {
HITCBC 265   6814 mutex_type::scoped_lock lock(mutex_); 265   5178 mutex_type::scoped_lock lock(mutex_);
266   266  
HITCBC 267   6814 auto it = registered_descs_.find(fd); 267   5178 auto it = registered_descs_.find(fd);
HITCBC 268   6814 if (it == registered_descs_.end()) 268   5178 if (it == registered_descs_.end())
MISUBC 269   ✗ return; 269   ✗ return;
270   270  
HITCBC 271   6814 registered_descs_.erase(it); 271   5178 registered_descs_.erase(it);
272   272  
HITCBC 273   6814 if (fd == max_fd_) 273   5178 if (fd == max_fd_)
274   { 274   {
HITCBC 275   6624 max_fd_ = pipe_fds_[0]; 275   4841 max_fd_ = pipe_fds_[0];
HITCBC 276   12923 for (auto& [registered_fd, state] : registered_descs_) 276   9283 for (auto& [registered_fd, state] : registered_descs_)
277   { 277   {
HITCBC 278   6299 if (registered_fd > max_fd_) 278   4442 if (registered_fd > max_fd_)
HITCBC 279   6212 max_fd_ = registered_fd; 279   4349 max_fd_ = registered_fd;
280   } 280   }
281   } 281   }
HITCBC 282   6814 } 282   5178 }
283   283  
284   inline void 284   inline void
HITCBC 285   3233 select_scheduler::notify_reactor() const 285   2351 select_scheduler::notify_reactor() const
286   { 286   {
HITCBC 287   3233 interrupt_reactor(); 287   2351 interrupt_reactor();
HITCBC 288   3233 } 288   2351 }
289   289  
290   inline void 290   inline void
HITCBC 291   15373 select_scheduler::interrupt_reactor() const 291   12090 select_scheduler::interrupt_reactor() const
292   { 292   {
HITCBC 293   15373 char byte = 1; 293   12090 char byte = 1;
HITCBC 294   15373 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 294   12090 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 295   15373 } 295   12090 }
296   296  
297   inline long 297   inline long
HITCBC 298   337213 select_scheduler::calculate_timeout(long requested_timeout_us) const 298   331843 select_scheduler::calculate_timeout(long requested_timeout_us) const
299   { 299   {
HITCBC 300   337213 if (requested_timeout_us == 0) 300   331843 if (requested_timeout_us == 0)
MISUBC 301   ✗ return 0; 301   ✗ return 0;
302   302  
HITCBC 303   337213 auto nearest = timer_svc_->nearest_expiry(); 303   331843 auto nearest = timer_svc_->nearest_expiry();
HITCBC 304   337213 if (nearest == timer_service::time_point::max()) 304   331843 if (nearest == timer_service::time_point::max())
HITCBC 305   654 return requested_timeout_us; 305   733 return requested_timeout_us;
306   306  
HITCBC 307   336559 auto now = std::chrono::steady_clock::now(); 307   331110 auto now = std::chrono::steady_clock::now();
HITCBC 308   336559 if (nearest <= now) 308   331110 if (nearest <= now)
HITCBC 309   713 return 0; 309   519 return 0;
310   310  
311   auto timer_timeout_us = 311   auto timer_timeout_us =
HITCBC 312   335846 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 312   330591 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 313   335846 .count(); 313   330591 .count();
314   314  
HITCBC 315   335846 constexpr auto long_max = 315   330591 constexpr auto long_max =
316   static_cast<long long>((std::numeric_limits<long>::max)()); 316   static_cast<long long>((std::numeric_limits<long>::max)());
317   auto capped_timer_us = 317   auto capped_timer_us =
HITCBC 318   335846 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 318   330591 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 319   335846 static_cast<long long>(0)), 319   330591 static_cast<long long>(0)),
HITCBC 320   335846 long_max); 320   330591 long_max);
321   321  
HITCBC 322   335846 if (requested_timeout_us < 0) 322   330591 if (requested_timeout_us < 0)
HITCBC 323   335846 return static_cast<long>(capped_timer_us); 323   330589 return static_cast<long>(capped_timer_us);
324   324  
325   return static_cast<long>( 325   return static_cast<long>(
HITGBC 326   ✗ (std::min)(static_cast<long long>(requested_timeout_us), 326   2 (std::min)(static_cast<long long>(requested_timeout_us),
HITGBC 327   ✗ capped_timer_us)); 327   2 capped_timer_us));
328   } 328   }
329   329  
330   inline void 330   inline void
HITCBC 331   358924 select_scheduler::run_task( 331   356670 select_scheduler::run_task(
332 - lock_type& lock, context_type* ctx, long timeout_us) 332 + lock_type& lock, context_type& ctx, long timeout_us)
333   { 333   {
334   long effective_timeout_us = 334   long effective_timeout_us =
HITCBC 335   358924 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 335   356670 task_interrupted_ ? 0 : calculate_timeout(timeout_us);
336   336  
337   // Snapshot registered descriptors while holding lock. 337   // Snapshot registered descriptors while holding lock.
338   // Record which fds need write monitoring to avoid a hot loop: 338   // Record which fds need write monitoring to avoid a hot loop:
339   // select is level-triggered so writable sockets (nearly always 339   // select is level-triggered so writable sockets (nearly always
340   // writable) would cause select() to return immediately every 340   // writable) would cause select() to return immediately every
341   // iteration if unconditionally added to write_fds. Membership 341   // iteration if unconditionally added to write_fds. Membership
342   // stays opt-in: a parked write wait opts in the same way a 342   // stays opt-in: a parked write wait opts in the same way a
343   // parked write or connect op does. 343   // parked write or connect op does.
344   struct fd_entry 344   struct fd_entry
345   { 345   {
346   int fd; 346   int fd;
347   reactor_descriptor_state* desc; 347   reactor_descriptor_state* desc;
348   bool needs_write; 348   bool needs_write;
349   }; 349   };
350   fd_entry snapshot[FD_SETSIZE]; 350   fd_entry snapshot[FD_SETSIZE];
HITCBC 351   358924 int snapshot_count = 0; 351   356670 int snapshot_count = 0;
352   352  
HITCBC 353   905260 for (auto& [fd, desc] : registered_descs_) 353   912560 for (auto& [fd, desc] : registered_descs_)
354   { 354   {
HITCBC 355   546336 if (snapshot_count < FD_SETSIZE) 355   555890 if (snapshot_count < FD_SETSIZE)
356   { 356   {
HITCBC 357   546336 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 357   555890 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 358   546336 snapshot[snapshot_count].fd = fd; 358   555890 snapshot[snapshot_count].fd = fd;
HITCBC 359   546336 snapshot[snapshot_count].desc = desc; 359   555890 snapshot[snapshot_count].desc = desc;
HITCBC 360   546336 snapshot[snapshot_count].needs_write = 360   555890 snapshot[snapshot_count].needs_write =
HITCBC 361   1078837 (desc->write_op || desc->connect_op || 361   1098709 (desc->write_op || desc->connect_op ||
HITCBC 362   532501 desc->wait_write_op); 362   542819 desc->wait_write_op);
HITCBC 363   546336 ++snapshot_count; 363   555890 ++snapshot_count;
HITCBC 364   546336 } 364   555890 }
365   } 365   }
366   366  
HITCBC 367   358924 if (lock.owns_lock()) 367   356670 if (lock.owns_lock())
HITCBC 368   337214 lock.unlock(); 368   331844 lock.unlock();
369   369  
HITCBC 370   358924 task_cleanup on_exit{this, &lock, ctx}; 370   356670 task_cleanup on_exit{this, &lock, ctx};
371   371  
372   fd_set read_fds, write_fds, except_fds; 372   fd_set read_fds, write_fds, except_fds;
HITCBC 373   6101708 FD_ZERO(&read_fds); 373   6063390 FD_ZERO(&read_fds);
HITCBC 374   6101708 FD_ZERO(&write_fds); 374   6063390 FD_ZERO(&write_fds);
HITCBC 375   6101708 FD_ZERO(&except_fds); 375   6063390 FD_ZERO(&except_fds);
376   376  
HITCBC 377   358924 FD_SET(pipe_fds_[0], &read_fds); 377   356670 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 378   358924 int nfds = pipe_fds_[0]; 378   356670 int nfds = pipe_fds_[0];
379   379  
HITCBC 380   905260 for (int i = 0; i < snapshot_count; ++i) 380   912560 for (int i = 0; i < snapshot_count; ++i)
381   { 381   {
HITCBC 382   546336 int fd = snapshot[i].fd; 382   555890 int fd = snapshot[i].fd;
HITCBC 383   546336 FD_SET(fd, &read_fds); 383   555890 FD_SET(fd, &read_fds);
HITCBC 384   546336 if (snapshot[i].needs_write) 384   555890 if (snapshot[i].needs_write)
HITCBC 385   13841 FD_SET(fd, &write_fds); 385   13077 FD_SET(fd, &write_fds);
HITCBC 386   546336 FD_SET(fd, &except_fds); 386   555890 FD_SET(fd, &except_fds);
HITCBC 387   546336 if (fd > nfds) 387   555890 if (fd > nfds)
HITCBC 388   358479 nfds = fd; 388   356273 nfds = fd;
389   } 389   }
390   390  
391   struct timeval tv; 391   struct timeval tv;
HITCBC 392   358924 struct timeval* tv_ptr = nullptr; 392   356670 struct timeval* tv_ptr = nullptr;
HITCBC 393   358924 if (effective_timeout_us >= 0) 393   356670 if (effective_timeout_us >= 0)
394   { 394   {
HITCBC 395   358273 tv.tv_sec = effective_timeout_us / 1000000; 395   355953 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 396   358273 tv.tv_usec = effective_timeout_us % 1000000; 396   355953 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 397   358273 tv_ptr = &tv; 397   355953 tv_ptr = &tv;
398   } 398   }
399   399  
HITCBC 400   358924 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 400   356670 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
401   401  
402   // EINTR: signal interrupted select(), just retry. 402   // EINTR: signal interrupted select(), just retry.
403   // EBADF: an fd was closed between snapshot and select(); retry 403   // EBADF: an fd was closed between snapshot and select(); retry
404   // with a fresh snapshot from registered_descs_. 404   // with a fresh snapshot from registered_descs_.
405   // Both fall through with no ready descriptors rather than 405   // Both fall through with no ready descriptors rather than
406   // returning: the caller handed this function an owned lock that 406   // returning: the caller handed this function an owned lock that
407   // only the epilogue below re-acquires. 407   // only the epilogue below re-acquires.
HITCBC 408   358924 if (ready < 0) 408   356670 if (ready < 0)
409   { 409   {
HITCBC 410   3 if (errno != EINTR && errno != EBADF) 410   3 if (errno != EINTR && errno != EBADF)
HITCBC 411   1 detail::throw_system_error(make_err(errno), "select"); 411   1 detail::throw_system_error(make_err(errno), "select");
HITCBC 412   2 ready = 0; 412   2 ready = 0;
413   } 413   }
414   414  
415   // Process timers outside the lock 415   // Process timers outside the lock
HITCBC 416   358923 timer_svc_->process_expired(); 416   356669 timer_svc_->process_expired();
417   417  
HITCBC 418   358923 ready_queue local_ops; 418   356669 ready_queue local_ops;
419   419  
HITCBC 420   358923 if (ready > 0) 420   356669 if (ready > 0)
421   { 421   {
HITCBC 422   342110 if (FD_ISSET(pipe_fds_[0], &read_fds)) 422   339472 if (FD_ISSET(pipe_fds_[0], &read_fds))
423   { 423   {
424   char buf[256]; 424   char buf[256];
HITCBC 425   14154 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 425   10808 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
426   { 426   {
427   } 427   }
428   } 428   }
429   429  
HITCBC 430   841921 for (int i = 0; i < snapshot_count; ++i) 430   843531 for (int i = 0; i < snapshot_count; ++i)
431   { 431   {
HITCBC 432   499811 int fd = snapshot[i].fd; 432   504059 int fd = snapshot[i].fd;
HITCBC 433   499811 reactor_descriptor_state* desc = snapshot[i].desc; 433   504059 reactor_descriptor_state* desc = snapshot[i].desc;
434   434  
HITCBC 435   499811 std::uint32_t flags = 0; 435   504059 std::uint32_t flags = 0;
HITCBC 436   499811 if (FD_ISSET(fd, &read_fds)) 436   504059 if (FD_ISSET(fd, &read_fds))
HITCBC 437   338503 flags |= reactor_event_read; 437   338797 flags |= reactor_event_read;
HITCBC 438   499811 if (FD_ISSET(fd, &write_fds)) 438   504059 if (FD_ISSET(fd, &write_fds))
HITCBC 439   3228 flags |= reactor_event_write; 439   2343 flags |= reactor_event_write;
HITCBC 440   499811 if (FD_ISSET(fd, &except_fds)) 440   504059 if (FD_ISSET(fd, &except_fds))
HITCBC 441   16 flags |= reactor_event_error; 441   16 flags |= reactor_event_error;
442   442  
HITCBC 443   499811 if (flags == 0) 443   504059 if (flags == 0)
HITCBC 444   158088 continue; 444   162928 continue;
445   445  
HITCBC 446   341723 desc->add_ready_events(flags); 446   341131 desc->add_ready_events(flags);
447   447  
HITCBC 448   341723 bool expected = false; 448   341131 bool expected = false;
HITCBC 449   341723 if (desc->is_enqueued_.compare_exchange_strong( 449   341131 if (desc->is_enqueued_.compare_exchange_strong(
450   expected, true, std::memory_order_release, 450   expected, true, std::memory_order_release,
451   std::memory_order_relaxed)) 451   std::memory_order_relaxed))
452   { 452   {
HITCBC 453   341723 local_ops.push(desc); 453   341131 local_ops.push(desc);
454   } 454   }
455   } 455   }
456   } 456   }
457   457  
HITCBC 458   358923 lock.lock(); 458   356669 lock.lock();
459   459  
HITCBC 460   358923 completed_ops_.splice(local_ops); 460   356669 completed_ops_.splice(local_ops);
HITCBC 461   358924 } 461   356670 }
462   462  
463   } // namespace boost::corosio::detail 463   } // namespace boost::corosio::detail
464   464  
465   #endif // BOOST_COROSIO_HAS_SELECT 465   #endif // BOOST_COROSIO_HAS_SELECT
466   466  
467   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 467   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP