. /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   27  
28   #include <boost/corosio/detail/except.hpp> 28   #include <boost/corosio/detail/except.hpp>
29   29  
30   #include <sys/select.h> 30   #include <sys/select.h>
31   #include <unistd.h> 31   #include <unistd.h>
32   #include <errno.h> 32   #include <errno.h>
33   #include <fcntl.h> 33   #include <fcntl.h>
34   34  
35   #include <atomic> 35   #include <atomic>
36   #include <chrono> 36   #include <chrono>
37   #include <cstdint> 37   #include <cstdint>
38   #include <limits> 38   #include <limits>
39   #include <mutex> 39   #include <mutex>
40   #include <new> 40   #include <new>
41   #include <unordered_map> 41   #include <unordered_map>
42   42  
43   namespace boost::corosio::detail { 43   namespace boost::corosio::detail {
44   44  
45   struct select_op; 45   struct select_op;
46   46  
47   /** POSIX scheduler using select() for I/O multiplexing. 47   /** POSIX scheduler using select() for I/O multiplexing.
48   48  
49   This scheduler implements the scheduler interface using the POSIX select() 49   This scheduler implements the scheduler interface using the POSIX select()
50   call for I/O event notification. It inherits the shared reactor threading 50   call for I/O event notification. It inherits the shared reactor threading
51   model from reactor_scheduler: signal state machine, inline completion 51   model from reactor_scheduler: signal state machine, inline completion
52   budget, work counting, and the do_one event loop. 52   budget, work counting, and the do_one event loop.
53   53  
54   The design mirrors epoll_scheduler for behavioral consistency: 54   The design mirrors epoll_scheduler for behavioral consistency:
55   - Same single-reactor thread coordination model 55   - Same single-reactor thread coordination model
56   - Same deferred I/O pattern (reactor marks ready; workers do I/O) 56   - Same deferred I/O pattern (reactor marks ready; workers do I/O)
57   - Same timer integration pattern 57   - Same timer integration pattern
58   58  
59   Known Limitations: 59   Known Limitations:
60   - FD_SETSIZE (~1024) limits maximum concurrent connections 60   - FD_SETSIZE (~1024) limits maximum concurrent connections
61   - O(n) scanning: rebuilds fd_sets each iteration 61   - O(n) scanning: rebuilds fd_sets each iteration
62   - Level-triggered only (no edge-triggered mode) 62   - Level-triggered only (no edge-triggered mode)
63   63  
64   @par Thread Safety 64   @par Thread Safety
65   All public member functions are thread-safe. 65   All public member functions are thread-safe.
66   */ 66   */
67   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler 67   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler
68   { 68   {
69   public: 69   public:
70   /** Construct the scheduler. 70   /** Construct the scheduler.
71   71  
72   Creates a self-pipe for reactor interruption. 72   Creates a self-pipe for reactor interruption.
73   73  
74   @param ctx Reference to the owning execution_context. 74   @param ctx Reference to the owning execution_context.
75   @param concurrency_hint Hint for expected thread count (unused). 75   @param concurrency_hint Hint for expected thread count (unused).
76   */ 76   */
77   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1); 77   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
78   78  
79   /// Destroy the scheduler. 79   /// Destroy the scheduler.
80   ~select_scheduler() override; 80   ~select_scheduler() override;
81   81  
82   select_scheduler(select_scheduler const&) = delete; 82   select_scheduler(select_scheduler const&) = delete;
83   select_scheduler& operator=(select_scheduler const&) = delete; 83   select_scheduler& operator=(select_scheduler const&) = delete;
84   84  
85   /// Shut down the scheduler, draining pending operations. 85   /// Shut down the scheduler, draining pending operations.
86   void shutdown() override; 86   void shutdown() override;
87   87  
88   /** Return the maximum file descriptor value supported. 88   /** Return the maximum file descriptor value supported.
89   89  
90   Returns FD_SETSIZE - 1, the maximum fd value that can be 90   Returns FD_SETSIZE - 1, the maximum fd value that can be
91   monitored by select(). Operations with fd >= FD_SETSIZE 91   monitored by select(). Operations with fd >= FD_SETSIZE
92   will fail with EINVAL. 92   will fail with EINVAL.
93   93  
94   @return The maximum supported file descriptor value. 94   @return The maximum supported file descriptor value.
95   */ 95   */
96   static constexpr int max_fd() noexcept 96   static constexpr int max_fd() noexcept
97   { 97   {
98   return FD_SETSIZE - 1; 98   return FD_SETSIZE - 1;
99   } 99   }
100   100  
101   /** Register a descriptor for persistent monitoring. 101   /** Register a descriptor for persistent monitoring.
102   102  
103   The fd is added to the registered_descs_ map and will be 103   The fd is added to the registered_descs_ map and will be
104   included in subsequent select() calls. The reactor is 104   included in subsequent select() calls. The reactor is
105   interrupted so a blocked select() rebuilds its fd_sets. 105   interrupted so a blocked select() rebuilds its fd_sets.
106   106  
107   @param fd The file descriptor to register. 107   @param fd The file descriptor to register.
108   @param desc Pointer to descriptor state for this fd. 108   @param desc Pointer to descriptor state for this fd.
109   109  
110   @return The error if the fd cannot be tracked, otherwise a 110   @return The error if the fd cannot be tracked, otherwise a
111   default constructed error code. 111   default constructed error code.
112   */ 112   */
113   std::error_code 113   std::error_code
114   register_descriptor(int fd, reactor_descriptor_state* desc) const; 114   register_descriptor(int fd, reactor_descriptor_state* desc) const;
115   115  
116   /// No-op: write readiness is watched from registration on. 116   /// No-op: write readiness is watched from registration on.
117   std::error_code 117   std::error_code
HITCBC 118   2766 ensure_write_registered(int, reactor_descriptor_state*) const noexcept 118   2753 ensure_write_registered(int, reactor_descriptor_state*) const noexcept
119   { 119   {
HITCBC 120   2766 return {}; 120   2753 return {};
121   } 121   }
122   122  
123   /** Deregister a persistently registered descriptor. 123   /** Deregister a persistently registered descriptor.
124   124  
125   @param fd The file descriptor to deregister. 125   @param fd The file descriptor to deregister.
126   */ 126   */
127   void deregister_descriptor(int fd) const; 127   void deregister_descriptor(int fd) const;
128   128  
129   /** Interrupt the reactor so it rebuilds its fd_sets. 129   /** Interrupt the reactor so it rebuilds its fd_sets.
130   130  
131   Called when a write, connect, or write-wait op is registered 131   Called when a write, connect, or write-wait op is registered
132   after the reactor's snapshot was taken. Without this, 132   after the reactor's snapshot was taken. Without this,
133   select() may block not watching for writability on the fd. 133   select() may block not watching for writability on the fd.
134   */ 134   */
135   void notify_reactor() const; 135   void notify_reactor() const;
136   136  
137   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp). 137   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp).
HITCBC 138   274 [[nodiscard]] std::error_code register_signal_reader(int read_fd) override 138   274 [[nodiscard]] std::error_code register_signal_reader(int read_fd) override
139   { 139   {
HITCBC 140   274 return register_descriptor(read_fd, signal_pipe_reader_.arm()); 140   274 return register_descriptor(read_fd, signal_pipe_reader_.arm());
141   } 141   }
142   142  
143   private: 143   private:
144   void run_task(lock_type& lock, context_type& ctx, long timeout_us) override; 144   void run_task(lock_type& lock, context_type& ctx, long timeout_us) override;
145   void interrupt_reactor() const override; 145   void interrupt_reactor() const override;
146   146  
147   /// Rebuild the poll set a blocked select() was given. 147   /// Rebuild the poll set a blocked select() was given.
HITCBC 148   598 void notify_reparked() const override 148   447 void notify_reparked() const override
149   { 149   {
HITCBC 150   598 interrupt_reactor(); 150   447 interrupt_reactor();
HITCBC 151   598 } 151   447 }
152   long calculate_timeout(long requested_timeout_us) const; 152   long calculate_timeout(long requested_timeout_us) const;
153   153  
154   // Watches the global signal self-pipe's read end (armed lazily by 154   // Watches the global signal self-pipe's read end (armed lazily by
155   // register_signal_reader on the first signal registration). 155   // register_signal_reader on the first signal registration).
156   reactor_signal_pipe_reader signal_pipe_reader_; 156   reactor_signal_pipe_reader signal_pipe_reader_;
157   157  
158   // Self-pipe for interrupting select() 158   // Self-pipe for interrupting select()
159   int pipe_fds_[2]; // [0]=read, [1]=write 159   int pipe_fds_[2]; // [0]=read, [1]=write
160   160  
161   // Per-fd tracking for fd_set building 161   // Per-fd tracking for fd_set building
162   mutable std::unordered_map<int, reactor_descriptor_state*> 162   mutable std::unordered_map<int, reactor_descriptor_state*>
163   registered_descs_; 163   registered_descs_;
164   mutable int max_fd_ = -1; 164   mutable int max_fd_ = -1;
165   }; 165   };
166   166  
HITCBC 167   1989 inline select_scheduler::select_scheduler(capy::execution_context&, int) 167   1989 inline select_scheduler::select_scheduler(capy::execution_context&, int)
HITCBC 168   1989 : pipe_fds_{-1, -1} 168   1989 : pipe_fds_{-1, -1}
HITCBC 169   1989 , max_fd_(-1) 169   1989 , max_fd_(-1)
170   { 170   {
HITCBC 171   1989 if (::pipe(pipe_fds_) < 0) 171   1989 if (::pipe(pipe_fds_) < 0)
HITCBC 172   1 detail::throw_system_error(make_err(errno), "pipe"); 172   1 detail::throw_system_error(make_err(errno), "pipe");
173   173  
HITCBC 174   5955 for (int i = 0; i < 2; ++i) 174   5955 for (int i = 0; i < 2; ++i)
175   { 175   {
HITCBC 176   3973 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 176   3973 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 177   3973 if (flags == -1) 177   3973 if (flags == -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_GETFL"); 182   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
183   } 183   }
HITCBC 184   3971 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 184   3971 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -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_SETFL"); 189   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
190   } 190   }
HITCBC 191   3969 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 191   3969 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
192   { 192   {
HITCBC 193   2 int errn = errno; 193   2 int errn = errno;
HITCBC 194   2 ::close(pipe_fds_[0]); 194   2 ::close(pipe_fds_[0]);
HITCBC 195   2 ::close(pipe_fds_[1]); 195   2 ::close(pipe_fds_[1]);
HITCBC 196   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD"); 196   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
197   } 197   }
198   } 198   }
199   199  
HITCBC 200   1982 completed_ops_.push(&task_op_); 200   1982 completed_ops_.push(&task_op_);
HITCBC 201   2003 } 201   2003 }
202   202  
HITCBC 203   3964 inline select_scheduler::~select_scheduler() 203   3964 inline select_scheduler::~select_scheduler()
204   { 204   {
HITCBC 205   1982 if (pipe_fds_[0] >= 0) 205   1982 if (pipe_fds_[0] >= 0)
HITCBC 206   1982 ::close(pipe_fds_[0]); 206   1982 ::close(pipe_fds_[0]);
HITCBC 207   1982 if (pipe_fds_[1] >= 0) 207   1982 if (pipe_fds_[1] >= 0)
HITCBC 208   1982 ::close(pipe_fds_[1]); 208   1982 ::close(pipe_fds_[1]);
HITCBC 209   3964 } 209   3964 }
210   210  
211   inline void 211   inline void
HITCBC 212   1982 select_scheduler::shutdown() 212   1982 select_scheduler::shutdown()
213   { 213   {
HITCBC 214   1982 shutdown_drain(); 214   1982 shutdown_drain();
215   215  
HITCBC 216   1982 if (pipe_fds_[1] >= 0) 216   1982 if (pipe_fds_[1] >= 0)
HITCBC 217   1982 interrupt_reactor(); 217   1982 interrupt_reactor();
HITCBC 218   1982 } 218   1982 }
219   219  
220   inline std::error_code 220   inline std::error_code
HITCBC 221   9947 select_scheduler::register_descriptor( 221   10027 select_scheduler::register_descriptor(
222   int fd, reactor_descriptor_state* desc) const 222   int fd, reactor_descriptor_state* desc) const
223   { 223   {
HITCBC 224   9947 if (fd < 0 || fd >= FD_SETSIZE) 224   10027 if (fd < 0 || fd >= FD_SETSIZE)
HITCBC 225   1 return make_err(EMFILE); 225   1 return make_err(EMFILE);
226   226  
227   // A completion queued by an earlier registration of the same state 227   // A completion queued by an earlier registration of the same state
228   // may still be running, so the fields it reads change under its 228   // may still be running, so the fields it reads change under its
229   // mutex, and the mutex mode is only written when it differs. 229   // mutex, and the mutex mode is only written when it differs.
HITCBC 230   9946 if (desc->mutex.enabled() != reactor_io_locking_) 230   10026 if (desc->mutex.enabled() != reactor_io_locking_)
HITCBC 231   3 desc->mutex.set_enabled(reactor_io_locking_); 231   3 desc->mutex.set_enabled(reactor_io_locking_);
232   { 232   {
HITCBC 233   9946 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 233   10026 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 234   9946 desc->registered_events = reactor_event_read | reactor_event_write; 234   10026 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 235   9946 desc->unpollable = false; // the state is reused across adoptions 235   10026 desc->unpollable = false; // the state is reused across adoptions
HITCBC 236   9946 desc->fd = fd; 236   10026 desc->fd = fd;
HITCBC 237   9946 desc->scheduler_ = this; 237   10026 desc->scheduler_ = this;
HITCBC 238   9946 desc->ready_events_.store(0, std::memory_order_release); 238   10026 desc->ready_events_.store(0, std::memory_order_release);
239   // object_ref_ is not touched: a queued invocation from an 239   // object_ref_ is not touched: a queued invocation from an
240   // earlier registration still owns the reference in it. 240   // earlier registration still owns the reference in it.
HITCBC 241   9946 desc->read_ready = false; 241   10026 desc->read_ready = false;
HITCBC 242   9946 desc->write_ready = false; 242   10026 desc->write_ready = false;
HITCBC 243   9946 } 243   10026 }
244   244  
245   { 245   {
HITCBC 246   9946 mutex_type::scoped_lock lock(mutex_); 246   10026 mutex_type::scoped_lock lock(mutex_);
247   try 247   try
248   { 248   {
HITCBC 249   9946 registered_descs_[fd] = desc; 249   10026 registered_descs_[fd] = desc;
250   } 250   }
HITCBC 251   1 catch (std::bad_alloc const&) 251   1 catch (std::bad_alloc const&)
252   { 252   {
HITCBC 253   1 return make_err(ENOMEM); 253   1 return make_err(ENOMEM);
HITCBC 254   1 } 254   1 }
HITCBC 255   9945 if (fd > max_fd_) 255   10025 if (fd > max_fd_)
HITCBC 256   9465 max_fd_ = fd; 256   9499 max_fd_ = fd;
HITCBC 257   9946 } 257   10026 }
258   258  
HITCBC 259   9945 interrupt_reactor(); 259   10025 interrupt_reactor();
HITCBC 260   9945 return {}; 260   10025 return {};
261   } 261   }
262   262  
263   inline void 263   inline void
HITCBC 264   9672 select_scheduler::deregister_descriptor(int fd) const 264   9752 select_scheduler::deregister_descriptor(int fd) const
265   { 265   {
HITCBC 266   9672 mutex_type::scoped_lock lock(mutex_); 266   9752 mutex_type::scoped_lock lock(mutex_);
267   267  
HITCBC 268   9672 auto it = registered_descs_.find(fd); 268   9752 auto it = registered_descs_.find(fd);
HITCBC 269   9672 if (it == registered_descs_.end()) 269   9752 if (it == registered_descs_.end())
MISUBC 270   ✗ return; 270   ✗ return;
271   271  
HITCBC 272   9672 registered_descs_.erase(it); 272   9752 registered_descs_.erase(it);
273   273  
HITCBC 274   9672 if (fd == max_fd_) 274   9752 if (fd == max_fd_)
275   { 275   {
HITCBC 276   7836 max_fd_ = pipe_fds_[0]; 276   7851 max_fd_ = pipe_fds_[0];
HITCBC 277   13115 for (auto& [registered_fd, state] : registered_descs_) 277   13134 for (auto& [registered_fd, state] : registered_descs_)
278   { 278   {
HITCBC 279   5279 if (registered_fd > max_fd_) 279   5283 if (registered_fd > max_fd_)
HITCBC 280   5016 max_fd_ = registered_fd; 280   5016 max_fd_ = registered_fd;
281   } 281   }
282   } 282   }
HITCBC 283   9672 } 283   9752 }
284   284  
285   inline void 285   inline void
HITCBC 286   6822 select_scheduler::notify_reactor() const 286   6787 select_scheduler::notify_reactor() const
287   { 287   {
HITCBC 288   6822 interrupt_reactor(); 288   6787 interrupt_reactor();
HITCBC 289   6822 } 289   6787 }
290   290  
291   inline void 291   inline void
HITCBC 292   25824 select_scheduler::interrupt_reactor() const 292   25705 select_scheduler::interrupt_reactor() const
293   { 293   {
HITCBC 294   25824 char byte = 1; 294   25705 char byte = 1;
HITCBC 295   25824 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 295   25705 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 296   25824 } 296   25705 }
297   297  
298   inline long 298   inline long
HITCBC 299   24896 select_scheduler::calculate_timeout(long requested_timeout_us) const 299   22865 select_scheduler::calculate_timeout(long requested_timeout_us) const
300   { 300   {
HITCBC 301   24896 if (requested_timeout_us == 0) 301   22865 if (requested_timeout_us == 0)
302   return 0; // LCOV_EXCL_LINE run_task passes 0 via task_interrupted_, never through this argument 302   return 0; // LCOV_EXCL_LINE run_task passes 0 via task_interrupted_, never through this argument
303   303  
HITCBC 304   24896 auto* tsvc = timers(); 304   22865 auto* tsvc = timers();
HITCBC 305   24896 if (!tsvc) 305   22865 if (!tsvc)
HITCBC 306   18182 return requested_timeout_us; 306   16196 return requested_timeout_us;
HITCBC 307   6714 auto nearest = tsvc->nearest_expiry(); 307   6669 auto nearest = tsvc->nearest_expiry();
HITCBC 308   6714 if (nearest == timer_service::time_point::max()) 308   6669 if (nearest == timer_service::time_point::max())
HITCBC 309   137 return requested_timeout_us; 309   136 return requested_timeout_us;
310   310  
HITCBC 311   6577 auto now = std::chrono::steady_clock::now(); 311   6533 auto now = std::chrono::steady_clock::now();
HITCBC 312   6577 if (nearest <= now) 312   6533 if (nearest <= now)
HITCBC 313   62 return 0; 313   64 return 0;
314   314  
315   auto timer_timeout_us = 315   auto timer_timeout_us =
HITCBC 316   6515 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 316   6469 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 317   6515 .count(); 317   6469 .count();
318   318  
HITCBC 319   6515 constexpr auto long_max = 319   6469 constexpr auto long_max =
320   static_cast<long long>((std::numeric_limits<long>::max)()); 320   static_cast<long long>((std::numeric_limits<long>::max)());
321   auto capped_timer_us = 321   auto capped_timer_us =
HITCBC 322   6515 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 322   6469 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 323   6515 static_cast<long long>(0)), 323   6469 static_cast<long long>(0)),
HITCBC 324   6515 long_max); 324   6469 long_max);
325   325  
HITCBC 326   6515 if (requested_timeout_us < 0) 326   6469 if (requested_timeout_us < 0)
HITCBC 327   6509 return static_cast<long>(capped_timer_us); 327   6463 return static_cast<long>(capped_timer_us);
328   328  
329   return static_cast<long>( 329   return static_cast<long>(
HITCBC 330   6 (std::min)(static_cast<long long>(requested_timeout_us), 330   6 (std::min)(static_cast<long long>(requested_timeout_us),
HITCBC 331   6 capped_timer_us)); 331   6 capped_timer_us));
332   } 332   }
333   333  
334   inline void 334   inline void
HITCBC 335   151398 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us) 335   151586 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us)
336   { 336   {
337   long effective_timeout_us = 337   long effective_timeout_us =
HITCBC 338   151398 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 338   151586 task_interrupted_ ? 0 : calculate_timeout(timeout_us);
339   339  
340   // Snapshot registered descriptors while holding lock. 340   // Snapshot registered descriptors while holding lock.
341   // Record which directions each fd needs monitored to avoid a hot 341   // Record which directions each fd needs monitored to avoid a hot
342   // loop: select is level-triggered, so a writable socket (nearly 342   // loop: select is level-triggered, so a writable socket (nearly
343   // always writable) or an always-readable fd (/dev/zero, a pipe at 343   // always writable) or an always-readable fd (/dev/zero, a pipe at
344   // EOF) would return select() immediately every iteration if 344   // EOF) would return select() immediately every iteration if
345   // unconditionally added. Membership in both sets is opt-in: a 345   // unconditionally added. Membership in both sets is opt-in: a
346   // parked op or wait in a direction opts that direction in. The 346   // parked op or wait in a direction opts that direction in. The
347   // exceptional set is opt-in too, for any parked op or wait: 347   // exceptional set is opt-in too, for any parked op or wait:
348   // Darwin reports a character device (/dev/zero, /dev/null) as 348   // Darwin reports a character device (/dev/zero, /dev/null) as
349   // exceptional on every call. 349   // exceptional on every call.
350   struct fd_entry 350   struct fd_entry
351   { 351   {
352   int fd; 352   int fd;
353   reactor_descriptor_state* desc; 353   reactor_descriptor_state* desc;
354   std::uint32_t want; 354   std::uint32_t want;
355   }; 355   };
356   fd_entry snapshot[FD_SETSIZE]; 356   fd_entry snapshot[FD_SETSIZE];
HITCBC 357   151398 int snapshot_count = 0; 357   151586 int snapshot_count = 0;
358   358  
359   // The caller may have released the lock to hand queued work to a 359   // The caller may have released the lock to hand queued work to a
360   // peer, and deregister_descriptor() erases from this map under it. 360   // peer, and deregister_descriptor() erases from this map under it.
HITCBC 361   151398 if (!lock.owns_lock()) 361   151586 if (!lock.owns_lock())
HITCBC 362   126499 lock.lock(); 362   128718 lock.lock();
363   363  
HITCBC 364   410536 for (auto& [fd, desc] : registered_descs_) 364   412866 for (auto& [fd, desc] : registered_descs_)
365   { 365   {
HITCBC 366   259138 if (snapshot_count < FD_SETSIZE) 366   261280 if (snapshot_count < FD_SETSIZE)
367   { 367   {
HITCBC 368   259138 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 368   261280 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 369   259138 snapshot[snapshot_count].fd = fd; 369   261280 snapshot[snapshot_count].fd = fd;
HITCBC 370   259138 snapshot[snapshot_count].desc = desc; 370   261280 snapshot[snapshot_count].desc = desc;
HITCBC 371   259138 snapshot[snapshot_count].want = 371   261280 snapshot[snapshot_count].want =
HITCBC 372   259138 ((desc->read_op || desc->wait_read_op) ? reactor_event_read 372   261280 ((desc->read_op || desc->wait_read_op) ? reactor_event_read
HITCBC 373   259138 : 0) | 373   261280 : 0) |
HITCBC 374   258764 ((desc->write_op || desc->connect_op || desc->wait_write_op) 374   260906 ((desc->write_op || desc->connect_op || desc->wait_write_op)
HITCBC 375   517902 ? reactor_event_write 375   522186 ? reactor_event_write
HITCBC 376   259138 : 0) | 376   261280 : 0) |
HITCBC 377   259138 (desc->wait_error_op ? reactor_event_error : 0); 377   261280 (desc->wait_error_op ? reactor_event_error : 0);
HITCBC 378   259138 ++snapshot_count; 378   261280 ++snapshot_count;
HITCBC 379   259138 } 379   261280 }
380   } 380   }
381   381  
HITCBC 382   151398 if (lock.owns_lock()) 382   151586 if (lock.owns_lock())
HITCBC 383   151397 lock.unlock(); 383   151585 lock.unlock();
384   384  
HITCBC 385   151398 task_cleanup on_exit{this, &lock, ctx}; 385   151586 task_cleanup on_exit{this, &lock, ctx};
386   386  
387   fd_set read_fds, write_fds, except_fds; 387   fd_set read_fds, write_fds, except_fds;
HITCBC 388   2573766 FD_ZERO(&read_fds); 388   2576962 FD_ZERO(&read_fds);
HITCBC 389   2573766 FD_ZERO(&write_fds); 389   2576962 FD_ZERO(&write_fds);
HITCBC 390   2573766 FD_ZERO(&except_fds); 390   2576962 FD_ZERO(&except_fds);
391   391  
HITCBC 392   151398 FD_SET(pipe_fds_[0], &read_fds); 392   151586 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 393   151398 int nfds = pipe_fds_[0]; 393   151586 int nfds = pipe_fds_[0];
394   394  
HITCBC 395   410536 for (int i = 0; i < snapshot_count; ++i) 395   412866 for (int i = 0; i < snapshot_count; ++i)
396   { 396   {
HITCBC 397   259138 int fd = snapshot[i].fd; 397   261280 int fd = snapshot[i].fd;
HITCBC 398   259138 if (snapshot[i].want & reactor_event_read) 398   261280 if (snapshot[i].want & reactor_event_read)
HITCBC 399   123989 FD_SET(fd, &read_fds); 399   122141 FD_SET(fd, &read_fds);
HITCBC 400   259138 if (snapshot[i].want & reactor_event_write) 400   261280 if (snapshot[i].want & reactor_event_write)
HITCBC 401   3030 FD_SET(fd, &write_fds); 401   3017 FD_SET(fd, &write_fds);
HITCBC 402   259138 if (snapshot[i].want != 0) 402   261280 if (snapshot[i].want != 0)
HITCBC 403   127214 FD_SET(fd, &except_fds); 403   125353 FD_SET(fd, &except_fds);
HITCBC 404   259138 if (fd > nfds) 404   261280 if (fd > nfds)
HITCBC 405   148375 nfds = fd; 405   149626 nfds = fd;
406   } 406   }
407   407  
408   struct timeval tv; 408   struct timeval tv;
HITCBC 409   151398 struct timeval* tv_ptr = nullptr; 409   151586 struct timeval* tv_ptr = nullptr;
HITCBC 410   151398 if (effective_timeout_us >= 0) 410   151586 if (effective_timeout_us >= 0)
411   { 411   {
HITCBC 412   133738 tv.tv_sec = effective_timeout_us / 1000000; 412   135924 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 413   133738 tv.tv_usec = effective_timeout_us % 1000000; 413   135924 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 414   133738 tv_ptr = &tv; 414   135924 tv_ptr = &tv;
415   } 415   }
416   416  
HITCBC 417   151398 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 417   151586 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
418   418  
419   // EINTR: signal interrupted select(), just retry. 419   // EINTR: signal interrupted select(), just retry.
420   // EBADF: an fd was closed between snapshot and select(); retry 420   // EBADF: an fd was closed between snapshot and select(); retry
421   // with a fresh snapshot from registered_descs_. 421   // with a fresh snapshot from registered_descs_.
422   // Both fall through with no ready descriptors rather than 422   // Both fall through with no ready descriptors rather than
423   // returning: the caller handed this function an owned lock that 423   // returning: the caller handed this function an owned lock that
424   // only the epilogue below re-acquires. 424   // only the epilogue below re-acquires.
HITCBC 425   151398 if (ready < 0) 425   151586 if (ready < 0)
426   { 426   {
HITCBC 427   3 if (errno != EINTR && errno != EBADF) 427   3 if (errno != EINTR && errno != EBADF)
HITCBC 428   1 detail::throw_system_error(make_err(errno), "select"); 428   1 detail::throw_system_error(make_err(errno), "select");
HITCBC 429   2 ready = 0; 429   2 ready = 0;
430   } 430   }
431   431  
432   // Process timers outside the lock 432   // Process timers outside the lock
HITCBC 433   151397 if (auto* tsvc = timers()) 433   151585 if (auto* tsvc = timers())
HITCBC 434   28400 tsvc->process_expired(); 434   30486 tsvc->process_expired();
435   435  
HITCBC 436   151397 ready_queue local_ops; 436   151585 ready_queue local_ops;
437   437  
HITCBC 438   151397 if (ready > 0) 438   151585 if (ready > 0)
439   { 439   {
HITCBC 440   25191 if (FD_ISSET(pipe_fds_[0], &read_fds)) 440   23210 if (FD_ISSET(pipe_fds_[0], &read_fds))
441   { 441   {
442   char buf[256]; 442   char buf[256];
HITCBC 443   22786 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 443   22518 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
444   { 444   {
445   } 445   }
446   } 446   }
447   447  
HITCBC 448   119079 for (int i = 0; i < snapshot_count; ++i) 448   113870 for (int i = 0; i < snapshot_count; ++i)
449   { 449   {
HITCBC 450   93888 int fd = snapshot[i].fd; 450   90660 int fd = snapshot[i].fd;
HITCBC 451   93888 reactor_descriptor_state* desc = snapshot[i].desc; 451   90660 reactor_descriptor_state* desc = snapshot[i].desc;
452   452  
HITCBC 453   93888 std::uint32_t flags = 0; 453   90660 std::uint32_t flags = 0;
HITCBC 454   93888 if (FD_ISSET(fd, &read_fds)) 454   90660 if (FD_ISSET(fd, &read_fds))
HITCBC 455   16698 flags |= reactor_event_read; 455   14738 flags |= reactor_event_read;
HITCBC 456   93888 if (FD_ISSET(fd, &write_fds)) 456   90660 if (FD_ISSET(fd, &write_fds))
HITCBC 457   2746 flags |= reactor_event_write; 457   2733 flags |= reactor_event_write;
HITCBC 458   93888 if (FD_ISSET(fd, &except_fds)) 458   90660 if (FD_ISSET(fd, &except_fds))
HITCBC 459   13 flags |= reactor_event_error; 459   15 flags |= reactor_event_error;
460   460  
HITCBC 461   93888 if (flags == 0) 461   90660 if (flags == 0)
HITCBC 462   74442 continue; 462   73187 continue;
463   463  
HITCBC 464   19446 desc->add_ready_events(flags); 464   17473 desc->add_ready_events(flags);
465   465  
HITCBC 466   19446 bool expected = false; 466   17473 bool expected = false;
HITCBC 467   19446 if (desc->is_enqueued_.compare_exchange_strong( 467   17473 if (desc->is_enqueued_.compare_exchange_strong(
468   expected, true, std::memory_order_release, 468   expected, true, std::memory_order_release,
469   std::memory_order_relaxed)) 469   std::memory_order_relaxed))
470   { 470   {
HITCBC 471   6454 local_ops.push(desc); 471   6272 local_ops.push(desc);
472   } 472   }
473   } 473   }
474   } 474   }
475   475  
HITCBC 476   151397 lock.lock(); 476   151585 lock.lock();
477   477  
HITCBC 478   151397 completed_ops_.splice(local_ops); 478   151585 completed_ops_.splice(local_ops);
HITCBC 479   151398 } 479   151586 }
480   480  
481   } // namespace boost::corosio::detail 481   } // namespace boost::corosio::detail
482   482  
483   #endif // BOOST_COROSIO_HAS_SELECT 483   #endif // BOOST_COROSIO_HAS_SELECT
484   484  
485   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 485   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP