. /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   942 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 159   886 : pipe_fds_{-1, -1} 159   942 : pipe_fds_{-1, -1}
HITCBC 160   886 , max_fd_(-1) 160   942 , max_fd_(-1)
161   { 161   {
HITCBC 162   886 if (::pipe(pipe_fds_) < 0) 162   942 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   2814 for (int i = 0; i < 2; ++i)
166   { 166   {
HITCBC 167   1767 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 167   1879 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 168   1767 if (flags == -1) 168   1879 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   1877 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   1875 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   935 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 192   879 timer_svc_->set_on_earliest_changed( 192   935 timer_svc_->set_on_earliest_changed(
HITCBC 193   3729 timer_service::callback(this, [](void* p) { 193   3635 timer_service::callback(this, [](void* p) {
HITCBC 194   2850 static_cast<select_scheduler*>(p)->interrupt_reactor(); 194   2700 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 195   2850 })); 195   2700 }));
196   196  
HITCBC 197   879 get_resolver_service(ctx, *this); 197   935 get_resolver_service(ctx, *this);
HITCBC 198   879 get_signal_service(ctx, *this); 198   935 get_signal_service(ctx, *this);
HITCBC 199   879 get_stream_file_service(ctx, *this); 199   935 get_stream_file_service(ctx, *this);
HITCBC 200   879 get_random_access_file_service(ctx, *this); 200   935 get_random_access_file_service(ctx, *this);
201   201  
HITCBC 202   879 completed_ops_.push(&task_op_); 202   935 completed_ops_.push(&task_op_);
HITCBC 203   900 } 203   956 }
204   204  
HITCBC 205   1758 inline select_scheduler::~select_scheduler() 205   1870 inline select_scheduler::~select_scheduler()
206   { 206   {
HITCBC 207   879 if (pipe_fds_[0] >= 0) 207   935 if (pipe_fds_[0] >= 0)
HITCBC 208   879 ::close(pipe_fds_[0]); 208   935 ::close(pipe_fds_[0]);
HITCBC 209   879 if (pipe_fds_[1] >= 0) 209   935 if (pipe_fds_[1] >= 0)
HITCBC 210   879 ::close(pipe_fds_[1]); 210   935 ::close(pipe_fds_[1]);
HITCBC 211   1758 } 211   1870 }
212   212  
213   inline void 213   inline void
HITCBC 214   879 select_scheduler::shutdown() 214   935 select_scheduler::shutdown()
215   { 215   {
HITCBC 216   879 shutdown_drain(); 216   935 shutdown_drain();
217   217  
HITCBC 218   879 if (pipe_fds_[1] >= 0) 218   935 if (pipe_fds_[1] >= 0)
HITCBC 219   879 interrupt_reactor(); 219   935 interrupt_reactor();
HITCBC 220   879 } 220   935 }
221   221  
222   inline std::error_code 222   inline std::error_code
HITCBC 223   4795 select_scheduler::register_descriptor( 223   4808 select_scheduler::register_descriptor(
224   int fd, reactor_descriptor_state* desc) const 224   int fd, reactor_descriptor_state* desc) const
225   { 225   {
HITCBC 226   4795 if (fd < 0 || fd >= FD_SETSIZE) 226   4808 if (fd < 0 || fd >= FD_SETSIZE)
HITCBC 227   1 return make_err(EMFILE); 227   1 return make_err(EMFILE);
228   228  
HITCBC 229   4794 desc->registered_events = reactor_event_read | reactor_event_write; 229   4807 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 230   4794 desc->fd = fd; 230   4807 desc->fd = fd;
HITCBC 231   4794 desc->scheduler_ = this; 231   4807 desc->scheduler_ = this;
HITCBC 232   4794 desc->mutex.set_enabled(reactor_io_locking_); 232   4807 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 233   4794 desc->ready_events_.store(0, std::memory_order_relaxed); 233   4807 desc->ready_events_.store(0, std::memory_order_relaxed);
234   234  
235   { 235   {
HITCBC 236   4794 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 236   4807 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 237   4794 desc->impl_ref_.reset(); 237   4807 desc->impl_ref_.reset();
HITCBC 238   4794 desc->read_ready = false; 238   4807 desc->read_ready = false;
HITCBC 239   4794 desc->write_ready = false; 239   4807 desc->write_ready = false;
HITCBC 240   4794 } 240   4807 }
241   241  
242   { 242   {
HITCBC 243   4794 mutex_type::scoped_lock lock(mutex_); 243   4807 mutex_type::scoped_lock lock(mutex_);
244   try 244   try
245   { 245   {
HITCBC 246   4794 registered_descs_[fd] = desc; 246   4807 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   4793 if (fd > max_fd_) 252   4806 if (fd > max_fd_)
HITCBC 253   4739 max_fd_ = fd; 253   4752 max_fd_ = fd;
HITCBC 254   4794 } 254   4807 }
255   255  
HITCBC 256   4793 interrupt_reactor(); 256   4806 interrupt_reactor();
HITCBC 257   4793 return {}; 257   4806 return {};
258   } 258   }
259   259  
260   inline void 260   inline void
HITCBC 261   4739 select_scheduler::deregister_descriptor(int fd) const 261   4752 select_scheduler::deregister_descriptor(int fd) const
262   { 262   {
HITCBC 263   4739 mutex_type::scoped_lock lock(mutex_); 263   4752 mutex_type::scoped_lock lock(mutex_);
264   264  
HITCBC 265   4739 auto it = registered_descs_.find(fd); 265   4752 auto it = registered_descs_.find(fd);
HITCBC 266   4739 if (it == registered_descs_.end()) 266   4752 if (it == registered_descs_.end())
MISUBC 267   ✗ return; 267   ✗ return;
268   268  
HITCBC 269   4739 registered_descs_.erase(it); 269   4752 registered_descs_.erase(it);
270   270  
HITCBC 271   4739 if (fd == max_fd_) 271   4752 if (fd == max_fd_)
272   { 272   {
HITCBC 273   4403 max_fd_ = pipe_fds_[0]; 273   4407 max_fd_ = pipe_fds_[0];
HITCBC 274   8404 for (auto& [registered_fd, state] : registered_descs_) 274   8407 for (auto& [registered_fd, state] : registered_descs_)
275   { 275   {
HITCBC 276   4001 if (registered_fd > max_fd_) 276   4000 if (registered_fd > max_fd_)
HITCBC 277   3908 max_fd_ = registered_fd; 277   3907 max_fd_ = registered_fd;
278   } 278   }
279   } 279   }
HITCBC 280   4739 } 280   4752 }
281   281  
282   inline void 282   inline void
HITCBC 283   2129 select_scheduler::notify_reactor() const 283   2133 select_scheduler::notify_reactor() const
284   { 284   {
HITCBC 285   2129 interrupt_reactor(); 285   2133 interrupt_reactor();
HITCBC 286   2129 } 286   2133 }
287   287  
288   inline void 288   inline void
HITCBC 289   11446 select_scheduler::interrupt_reactor() const 289   11557 select_scheduler::interrupt_reactor() const
290   { 290   {
HITCBC 291   11446 char byte = 1; 291   11557 char byte = 1;
HITCBC 292   11446 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 292   11557 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 293   11446 } 293   11557 }
294   294  
295   inline long 295   inline long
HITCBC 296   289260 select_scheduler::calculate_timeout(long requested_timeout_us) const 296   280167 select_scheduler::calculate_timeout(long requested_timeout_us) const
297   { 297   {
HITCBC 298   289260 if (requested_timeout_us == 0) 298   280167 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   289260 auto nearest = timer_svc_->nearest_expiry(); 301   280167 auto nearest = timer_svc_->nearest_expiry();
HITCBC 302   289260 if (nearest == timer_service::time_point::max()) 302   280167 if (nearest == timer_service::time_point::max())
HITCBC 303   730 return requested_timeout_us; 303   795 return requested_timeout_us;
304   304  
HITCBC 305   288530 auto now = std::chrono::steady_clock::now(); 305   279372 auto now = std::chrono::steady_clock::now();
HITCBC 306   288530 if (nearest <= now) 306   279372 if (nearest <= now)
HITCBC 307   619 return 0; 307   626 return 0;
308   308  
309   auto timer_timeout_us = 309   auto timer_timeout_us =
HITCBC 310   287911 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 310   278746 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 311   287911 .count(); 311   278746 .count();
312   312  
HITCBC 313   287911 constexpr auto long_max = 313   278746 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   287911 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 316   278746 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 317   287911 static_cast<long long>(0)), 317   278746 static_cast<long long>(0)),
HITCBC 318   287911 long_max); 318   278746 long_max);
319   319  
HITCBC 320   287911 if (requested_timeout_us < 0) 320   278746 if (requested_timeout_us < 0)
HITCBC 321   287909 return static_cast<long>(capped_timer_us); 321   278744 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   313198 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us) 329   302437 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   313198 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 332   302437 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   313198 int snapshot_count = 0; 348   302437 int snapshot_count = 0;
349   349  
HITCBC 350   824322 for (auto& [fd, desc] : registered_descs_) 350   798010 for (auto& [fd, desc] : registered_descs_)
351   { 351   {
HITCBC 352   511124 if (snapshot_count < FD_SETSIZE) 352   495573 if (snapshot_count < FD_SETSIZE)
353   { 353   {
HITCBC 354   511124 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 354   495573 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 355   511124 snapshot[snapshot_count].fd = fd; 355   495573 snapshot[snapshot_count].fd = fd;
HITCBC 356   511124 snapshot[snapshot_count].desc = desc; 356   495573 snapshot[snapshot_count].desc = desc;
HITCBC 357   511124 snapshot[snapshot_count].needs_write = 357   495573 snapshot[snapshot_count].needs_write =
HITCBC 358   511124 (desc->write_op || desc->connect_op || desc->wait_write_op); 358   495573 (desc->write_op || desc->connect_op || desc->wait_write_op);
HITCBC 359   511124 ++snapshot_count; 359   495573 ++snapshot_count;
HITCBC 360   511124 } 360   495573 }
361   } 361   }
362   362  
HITCBC 363   313198 if (lock.owns_lock()) 363   302437 if (lock.owns_lock())
HITCBC 364   289261 lock.unlock(); 364   280168 lock.unlock();
365   365  
HITCBC 366   313198 task_cleanup on_exit{this, &lock, ctx}; 366   302437 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   5324366 FD_ZERO(&read_fds); 369   5141429 FD_ZERO(&read_fds);
HITCBC 370   5324366 FD_ZERO(&write_fds); 370   5141429 FD_ZERO(&write_fds);
HITCBC 371   5324366 FD_ZERO(&except_fds); 371   5141429 FD_ZERO(&except_fds);
372   372  
HITCBC 373   313198 FD_SET(pipe_fds_[0], &read_fds); 373   302437 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 374   313198 int nfds = pipe_fds_[0]; 374   302437 int nfds = pipe_fds_[0];
375   375  
HITCBC 376   824322 for (int i = 0; i < snapshot_count; ++i) 376   798010 for (int i = 0; i < snapshot_count; ++i)
377   { 377   {
HITCBC 378   511124 int fd = snapshot[i].fd; 378   495573 int fd = snapshot[i].fd;
HITCBC 379   511124 FD_SET(fd, &read_fds); 379   495573 FD_SET(fd, &read_fds);
HITCBC 380   511124 if (snapshot[i].needs_write) 380   495573 if (snapshot[i].needs_write)
HITCBC 381   12670 FD_SET(fd, &write_fds); 381   12094 FD_SET(fd, &write_fds);
HITCBC 382   511124 FD_SET(fd, &except_fds); 382   495573 FD_SET(fd, &except_fds);
HITCBC 383   511124 if (fd > nfds) 383   495573 if (fd > nfds)
HITCBC 384   312804 nfds = fd; 384   301833 nfds = fd;
385   } 385   }
386   386  
387   struct timeval tv; 387   struct timeval tv;
HITCBC 388   313198 struct timeval* tv_ptr = nullptr; 388   302437 struct timeval* tv_ptr = nullptr;
HITCBC 389   313198 if (effective_timeout_us >= 0) 389   302437 if (effective_timeout_us >= 0)
390   { 390   {
HITCBC 391   312484 tv.tv_sec = effective_timeout_us / 1000000; 391   301660 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 392   312484 tv.tv_usec = effective_timeout_us % 1000000; 392   301660 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 393   312484 tv_ptr = &tv; 393   301660 tv_ptr = &tv;
394   } 394   }
395   395  
HITCBC 396   313198 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 396   302437 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   313198 if (ready < 0) 404   302437 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   313197 timer_svc_->process_expired(); 412   302436 timer_svc_->process_expired();
413   413  
HITCBC 414   313197 ready_queue local_ops; 414   302436 ready_queue local_ops;
415   415  
HITCBC 416   313197 if (ready > 0) 416   302436 if (ready > 0)
417   { 417   {
HITCBC 418   297039 if (FD_ISSET(pipe_fds_[0], &read_fds)) 418   286898 if (FD_ISSET(pipe_fds_[0], &read_fds))
419   { 419   {
420   char buf[256]; 420   char buf[256];
HITCBC 421   9914 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 421   10190 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
422   { 422   {
423   } 423   }
424   } 424   }
425   425  
HITCBC 426   761075 for (int i = 0; i < snapshot_count; ++i) 426   733756 for (int i = 0; i < snapshot_count; ++i)
427   { 427   {
HITCBC 428   464036 int fd = snapshot[i].fd; 428   446858 int fd = snapshot[i].fd;
HITCBC 429   464036 reactor_descriptor_state* desc = snapshot[i].desc; 429   446858 reactor_descriptor_state* desc = snapshot[i].desc;
430   430  
HITCBC 431   464036 std::uint32_t flags = 0; 431   446858 std::uint32_t flags = 0;
HITCBC 432   464036 if (FD_ISSET(fd, &read_fds)) 432   446858 if (FD_ISSET(fd, &read_fds))
HITCBC 433   296627 flags |= reactor_event_read; 433   286306 flags |= reactor_event_read;
HITCBC 434   464036 if (FD_ISSET(fd, &write_fds)) 434   446858 if (FD_ISSET(fd, &write_fds))
HITCBC 435   2121 flags |= reactor_event_write; 435   2125 flags |= reactor_event_write;
HITCBC 436   464036 if (FD_ISSET(fd, &except_fds)) 436   446858 if (FD_ISSET(fd, &except_fds))
HITCBC 437   16 flags |= reactor_event_error; 437   16 flags |= reactor_event_error;
438   438  
HITCBC 439   464036 if (flags == 0) 439   446858 if (flags == 0)
HITCBC 440   165296 continue; 440   158435 continue;
441   441  
HITCBC 442   298740 desc->add_ready_events(flags); 442   288423 desc->add_ready_events(flags);
443   443  
HITCBC 444   298740 bool expected = false; 444   288423 bool expected = false;
HITCBC 445   298740 if (desc->is_enqueued_.compare_exchange_strong( 445   288423 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   298740 local_ops.push(desc); 449   288423 local_ops.push(desc);
450   } 450   }
451   } 451   }
452   } 452   }
453   453  
HITCBC 454   313197 lock.lock(); 454   302436 lock.lock();
455   455  
HITCBC 456   313197 completed_ops_.splice(local_ops); 456   302436 completed_ops_.splice(local_ops);
HITCBC 457   313198 } 457   302437 }
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