. /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   55 register_signal_reader(int read_fd) override 136   55 register_signal_reader(int read_fd) override
137   { 137   {
HITCBC 138   55 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   886 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int) 160   881 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 161   886 : pipe_fds_{-1, -1} 161   881 : pipe_fds_{-1, -1}
HITCBC 162   886 , max_fd_(-1) 162   881 , max_fd_(-1)
163   { 163   {
HITCBC 164   886 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   2646 for (int i = 0; i < 2; ++i) 167   2631 for (int i = 0; i < 2; ++i)
168   { 168   {
HITCBC 169   1767 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 169   1757 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 170   1767 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   1765 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   1763 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   879 timer_svc_ = &get_timer_service(ctx, *this); 193   874 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 194   879 timer_svc_->set_on_earliest_changed( 194   874 timer_svc_->set_on_earliest_changed(
HITCBC 195   3659 timer_service::callback(this, [](void* p) { 195   4254 timer_service::callback(this, [](void* p) {
HITCBC 196   2780 static_cast<select_scheduler*>(p)->interrupt_reactor(); 196   3380 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 197   2780 })); 197   3380 }));
198   198  
HITCBC 199   879 get_resolver_service(ctx, *this); 199   874 get_resolver_service(ctx, *this);
HITCBC 200   879 get_signal_service(ctx, *this); 200   874 get_signal_service(ctx, *this);
HITCBC 201   879 get_stream_file_service(ctx, *this); 201   874 get_stream_file_service(ctx, *this);
HITCBC 202   879 get_random_access_file_service(ctx, *this); 202   874 get_random_access_file_service(ctx, *this);
203   203  
HITCBC 204   879 completed_ops_.push(&task_op_); 204   874 completed_ops_.push(&task_op_);
HITCBC 205   900 } 205   895 }
206   206  
HITCBC 207   1758 inline select_scheduler::~select_scheduler() 207   1748 inline select_scheduler::~select_scheduler()
208   { 208   {
HITCBC 209   879 if (pipe_fds_[0] >= 0) 209   874 if (pipe_fds_[0] >= 0)
HITCBC 210   879 ::close(pipe_fds_[0]); 210   874 ::close(pipe_fds_[0]);
HITCBC 211   879 if (pipe_fds_[1] >= 0) 211   874 if (pipe_fds_[1] >= 0)
HITCBC 212   879 ::close(pipe_fds_[1]); 212   874 ::close(pipe_fds_[1]);
HITCBC 213   1758 } 213   1748 }
214   214  
215   inline void 215   inline void
HITCBC 216   879 select_scheduler::shutdown() 216   874 select_scheduler::shutdown()
217   { 217   {
HITCBC 218   879 shutdown_drain(); 218   874 shutdown_drain();
219   219  
HITCBC 220   879 if (pipe_fds_[1] >= 0) 220   874 if (pipe_fds_[1] >= 0)
HITCBC 221   879 interrupt_reactor(); 221   874 interrupt_reactor();
HITCBC 222   879 } 222   874 }
223   223  
224   inline std::error_code 224   inline std::error_code
HITCBC 225   4763 select_scheduler::register_descriptor( 225   5954 select_scheduler::register_descriptor(
226   int fd, reactor_descriptor_state* desc) const 226   int fd, reactor_descriptor_state* desc) const
227   { 227   {
HITCBC 228   4763 if (fd < 0 || fd >= FD_SETSIZE) 228   5954 if (fd < 0 || fd >= FD_SETSIZE)
HITCBC 229   1 return make_err(EMFILE); 229   1 return make_err(EMFILE);
230   230  
HITCBC 231   4762 desc->registered_events = reactor_event_read | reactor_event_write; 231   5953 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 232   4762 desc->fd = fd; 232   5953 desc->fd = fd;
HITCBC 233   4762 desc->scheduler_ = this; 233   5953 desc->scheduler_ = this;
HITCBC 234   4762 desc->mutex.set_enabled(reactor_io_locking_); 234   5953 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 235   4762 desc->ready_events_.store(0, std::memory_order_relaxed); 235   5953 desc->ready_events_.store(0, std::memory_order_relaxed);
236   236  
237   { 237   {
HITCBC 238   4762 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 238   5953 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 239   4762 desc->impl_ref_.reset(); 239   5953 desc->impl_ref_.reset();
HITCBC 240   4762 desc->read_ready = false; 240   5953 desc->read_ready = false;
HITCBC 241   4762 desc->write_ready = false; 241   5953 desc->write_ready = false;
HITCBC 242   4762 } 242   5953 }
243   243  
244   { 244   {
HITCBC 245   4762 mutex_type::scoped_lock lock(mutex_); 245   5953 mutex_type::scoped_lock lock(mutex_);
246   try 246   try
247   { 247   {
HITCBC 248   4762 registered_descs_[fd] = desc; 248   5953 registered_descs_[fd] = desc;
249   } 249   }
HITCBC 250   1 catch (std::bad_alloc const&) 250   1 catch (std::bad_alloc const&)
251   { 251   {
HITCBC 252   1 return make_err(ENOMEM); 252   1 return make_err(ENOMEM);
HITCBC 253   1 } 253   1 }
HITCBC 254   4761 if (fd > max_fd_) 254   5952 if (fd > max_fd_)
HITCBC 255   4707 max_fd_ = fd; 255   5898 max_fd_ = fd;
HITCBC 256   4762 } 256   5953 }
257   257  
HITCBC 258   4761 interrupt_reactor(); 258   5952 interrupt_reactor();
HITCBC 259   4761 return {}; 259   5952 return {};
260   } 260   }
261   261  
262   inline void 262   inline void
HITCBC 263   4707 select_scheduler::deregister_descriptor(int fd) const 263   5898 select_scheduler::deregister_descriptor(int fd) const
264   { 264   {
HITCBC 265   4707 mutex_type::scoped_lock lock(mutex_); 265   5898 mutex_type::scoped_lock lock(mutex_);
266   266  
HITCBC 267   4707 auto it = registered_descs_.find(fd); 267   5898 auto it = registered_descs_.find(fd);
HITCBC 268   4707 if (it == registered_descs_.end()) 268   5898 if (it == registered_descs_.end())
MISUBC 269   ✗ return; 269   ✗ return;
270   270  
HITCBC 271   4707 registered_descs_.erase(it); 271   5898 registered_descs_.erase(it);
272   272  
HITCBC 273   4707 if (fd == max_fd_) 273   5898 if (fd == max_fd_)
274   { 274   {
HITCBC 275   4371 max_fd_ = pipe_fds_[0]; 275   5561 max_fd_ = pipe_fds_[0];
HITCBC 276   8340 for (auto& [registered_fd, state] : registered_descs_) 276   10723 for (auto& [registered_fd, state] : registered_descs_)
277   { 277   {
HITCBC 278   3969 if (registered_fd > max_fd_) 278   5162 if (registered_fd > max_fd_)
HITCBC 279   3876 max_fd_ = registered_fd; 279   5069 max_fd_ = registered_fd;
280   } 280   }
281   } 281   }
HITCBC 282   4707 } 282   5898 }
283   283  
284   inline void 284   inline void
HITCBC 285   2113 select_scheduler::notify_reactor() const 285   2711 select_scheduler::notify_reactor() const
286   { 286   {
HITCBC 287   2113 interrupt_reactor(); 287   2711 interrupt_reactor();
HITCBC 288   2113 } 288   2711 }
289   289  
290   inline void 290   inline void
HITCBC 291   11339 select_scheduler::interrupt_reactor() const 291   13708 select_scheduler::interrupt_reactor() const
292   { 292   {
HITCBC 293   11339 char byte = 1; 293   13708 char byte = 1;
HITCBC 294   11339 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 294   13708 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 295   11339 } 295   13708 }
296   296  
297   inline long 297   inline long
HITCBC 298   356323 select_scheduler::calculate_timeout(long requested_timeout_us) const 298   344672 select_scheduler::calculate_timeout(long requested_timeout_us) const
299   { 299   {
HITCBC 300   356323 if (requested_timeout_us == 0) 300   344672 if (requested_timeout_us == 0)
MISUIC 301 - return 0; // LCOV_EXCL_LINE run_task passes 0 via task_interrupted_, never through this argument 301 + ✗ return 0;
302   302  
HITCBC 303   356323 auto nearest = timer_svc_->nearest_expiry(); 303   344672 auto nearest = timer_svc_->nearest_expiry();
HITCBC 304   356323 if (nearest == timer_service::time_point::max()) 304   344672 if (nearest == timer_service::time_point::max())
HITCBC 305   744 return requested_timeout_us; 305   730 return requested_timeout_us;
306   306  
HITCBC 307   355579 auto now = std::chrono::steady_clock::now(); 307   343942 auto now = std::chrono::steady_clock::now();
HITCBC 308   355579 if (nearest <= now) 308   343942 if (nearest <= now)
HITCBC 309   706 return 0; 309   761 return 0;
310   310  
311   auto timer_timeout_us = 311   auto timer_timeout_us =
HITCBC 312   354873 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 312   343181 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 313   354873 .count(); 313   343181 .count();
314   314  
HITCBC 315   354873 constexpr auto long_max = 315   343181 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   354873 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 318   343181 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 319   354873 static_cast<long long>(0)), 319   343181 static_cast<long long>(0)),
HITCBC 320   354873 long_max); 320   343181 long_max);
321   321  
HITCBC 322   354873 if (requested_timeout_us < 0) 322   343181 if (requested_timeout_us < 0)
HITCBC 323   354871 return static_cast<long>(capped_timer_us); 323   343179 return static_cast<long>(capped_timer_us);
324   324  
325   return static_cast<long>( 325   return static_cast<long>(
HITCBC 326   2 (std::min)(static_cast<long long>(requested_timeout_us), 326   2 (std::min)(static_cast<long long>(requested_timeout_us),
HITCBC 327   2 capped_timer_us)); 327   2 capped_timer_us));
328   } 328   }
329   329  
330   inline void 330   inline void
HITCBC 331   377290 select_scheduler::run_task( 331   366288 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   377290 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 335   366288 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   377290 int snapshot_count = 0; 351   366288 int snapshot_count = 0;
352   352  
HITCBC 353   952863 for (auto& [fd, desc] : registered_descs_) 353   917039 for (auto& [fd, desc] : registered_descs_)
354   { 354   {
HITCBC 355   575573 if (snapshot_count < FD_SETSIZE) 355   550751 if (snapshot_count < FD_SETSIZE)
356   { 356   {
HITCBC 357   575573 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 357   550751 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 358   575573 snapshot[snapshot_count].fd = fd; 358   550751 snapshot[snapshot_count].fd = fd;
HITCBC 359   575573 snapshot[snapshot_count].desc = desc; 359   550751 snapshot[snapshot_count].desc = desc;
HITCBC 360   575573 snapshot[snapshot_count].needs_write = 360   550751 snapshot[snapshot_count].needs_write =
HITCBC 361   1138140 (desc->write_op || desc->connect_op || 361   1090880 (desc->write_op || desc->connect_op ||
HITCBC 362   562567 desc->wait_write_op); 362   540129 desc->wait_write_op);
HITCBC 363   575573 ++snapshot_count; 363   550751 ++snapshot_count;
HITCBC 364   575573 } 364   550751 }
365   } 365   }
366   366  
HITCBC 367   377290 if (lock.owns_lock()) 367   366288 if (lock.owns_lock())
HITCBC 368   356324 lock.unlock(); 368   344673 lock.unlock();
369   369  
HITCBC 370   377290 task_cleanup on_exit{this, &lock, ctx}; 370   366288 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   6413930 FD_ZERO(&read_fds); 373   6226896 FD_ZERO(&read_fds);
HITCBC 374   6413930 FD_ZERO(&write_fds); 374   6226896 FD_ZERO(&write_fds);
HITCBC 375   6413930 FD_ZERO(&except_fds); 375   6226896 FD_ZERO(&except_fds);
376   376  
HITCBC 377   377290 FD_SET(pipe_fds_[0], &read_fds); 377   366288 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 378   377290 int nfds = pipe_fds_[0]; 378   366288 int nfds = pipe_fds_[0];
379   379  
HITCBC 380   952863 for (int i = 0; i < snapshot_count; ++i) 380   917039 for (int i = 0; i < snapshot_count; ++i)
381   { 381   {
HITCBC 382   575573 int fd = snapshot[i].fd; 382   550751 int fd = snapshot[i].fd;
HITCBC 383   575573 FD_SET(fd, &read_fds); 383   550751 FD_SET(fd, &read_fds);
HITCBC 384   575573 if (snapshot[i].needs_write) 384   550751 if (snapshot[i].needs_write)
HITCBC 385   13012 FD_SET(fd, &write_fds); 385   10628 FD_SET(fd, &write_fds);
HITCBC 386   575573 FD_SET(fd, &except_fds); 386   550751 FD_SET(fd, &except_fds);
HITCBC 387   575573 if (fd > nfds) 387   550751 if (fd > nfds)
HITCBC 388   376883 nfds = fd; 388   365895 nfds = fd;
389   } 389   }
390   390  
391   struct timeval tv; 391   struct timeval tv;
HITCBC 392   377290 struct timeval* tv_ptr = nullptr; 392   366288 struct timeval* tv_ptr = nullptr;
HITCBC 393   377290 if (effective_timeout_us >= 0) 393   366288 if (effective_timeout_us >= 0)
394   { 394   {
HITCBC 395   376563 tv.tv_sec = effective_timeout_us / 1000000; 395   365577 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 396   376563 tv.tv_usec = effective_timeout_us % 1000000; 396   365577 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 397   376563 tv_ptr = &tv; 397   365577 tv_ptr = &tv;
398   } 398   }
399   399  
HITCBC 400   377290 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 400   366288 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   377290 if (ready < 0) 408   366288 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   377289 timer_svc_->process_expired(); 416   366287 timer_svc_->process_expired();
417   417  
HITCBC 418   377289 ready_queue local_ops; 418   366287 ready_queue local_ops;
419   419  
HITCBC 420   377289 if (ready > 0) 420   366287 if (ready > 0)
421   { 421   {
HITCBC 422   362863 if (FD_ISSET(pipe_fds_[0], &read_fds)) 422   350674 if (FD_ISSET(pipe_fds_[0], &read_fds))
423   { 423   {
424   char buf[256]; 424   char buf[256];
HITCBC 425   9898 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 425   12242 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
426   { 426   {
427   } 427   }
428   } 428   }
429   429  
HITCBC 430   896857 for (int i = 0; i < snapshot_count; ++i) 430   858483 for (int i = 0; i < snapshot_count; ++i)
431   { 431   {
HITCBC 432   533994 int fd = snapshot[i].fd; 432   507809 int fd = snapshot[i].fd;
HITCBC 433   533994 reactor_descriptor_state* desc = snapshot[i].desc; 433   507809 reactor_descriptor_state* desc = snapshot[i].desc;
434   434  
HITCBC 435   533994 std::uint32_t flags = 0; 435   507809 std::uint32_t flags = 0;
HITCBC 436   533994 if (FD_ISSET(fd, &read_fds)) 436   507809 if (FD_ISSET(fd, &read_fds))
HITCBC 437   362471 flags |= reactor_event_read; 437   349716 flags |= reactor_event_read;
HITCBC 438   533994 if (FD_ISSET(fd, &write_fds)) 438   507809 if (FD_ISSET(fd, &write_fds))
HITCBC 439   2105 flags |= reactor_event_write; 439   2703 flags |= reactor_event_write;
HITCBC 440   533994 if (FD_ISSET(fd, &except_fds)) 440   507809 if (FD_ISSET(fd, &except_fds))
HITCBC 441   16 flags |= reactor_event_error; 441   16 flags |= reactor_event_error;
442   442  
HITCBC 443   533994 if (flags == 0) 443   507809 if (flags == 0)
HITCBC 444   169426 continue; 444   155399 continue;
445   445  
HITCBC 446   364568 desc->add_ready_events(flags); 446   352410 desc->add_ready_events(flags);
447   447  
HITCBC 448   364568 bool expected = false; 448   352410 bool expected = false;
HITCBC 449   364568 if (desc->is_enqueued_.compare_exchange_strong( 449   352410 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   364568 local_ops.push(desc); 453   352410 local_ops.push(desc);
454   } 454   }
455   } 455   }
456   } 456   }
457   457  
HITCBC 458   377289 lock.lock(); 458   366287 lock.lock();
459   459  
HITCBC 460   377289 completed_ops_.splice(local_ops); 460   366287 completed_ops_.splice(local_ops);
HITCBC 461   377290 } 461   366288 }
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