. /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   2755 ensure_write_registered(int, reactor_descriptor_state*) const noexcept 118   2785 ensure_write_registered(int, reactor_descriptor_state*) const noexcept
119   { 119   {
HITCBC 120   2755 return {}; 120   2785 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   383 void notify_reparked() const override 148   498 void notify_reparked() const override
149   { 149   {
HITCBC 150   383 interrupt_reactor(); 150   498 interrupt_reactor();
HITCBC 151   383 } 151   498 }
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   1993 inline select_scheduler::select_scheduler(capy::execution_context&, int) 167   1995 inline select_scheduler::select_scheduler(capy::execution_context&, int)
HITCBC 168   1993 : pipe_fds_{-1, -1} 168   1995 : pipe_fds_{-1, -1}
HITCBC 169   1993 , max_fd_(-1) 169   1995 , max_fd_(-1)
170   { 170   {
HITCBC 171   1993 if (::pipe(pipe_fds_) < 0) 171   1995 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   5967 for (int i = 0; i < 2; ++i) 174   5973 for (int i = 0; i < 2; ++i)
175   { 175   {
HITCBC 176   3981 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 176   3985 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 177   3981 if (flags == -1) 177   3985 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   3979 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 184   3983 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   3977 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 191   3981 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   1986 completed_ops_.push(&task_op_); 200   1988 completed_ops_.push(&task_op_);
HITCBC 201   2007 } 201   2009 }
202   202  
HITCBC 203   3972 inline select_scheduler::~select_scheduler() 203   3976 inline select_scheduler::~select_scheduler()
204   { 204   {
HITCBC 205   1986 if (pipe_fds_[0] >= 0) 205   1988 if (pipe_fds_[0] >= 0)
HITCBC 206   1986 ::close(pipe_fds_[0]); 206   1988 ::close(pipe_fds_[0]);
HITCBC 207   1986 if (pipe_fds_[1] >= 0) 207   1988 if (pipe_fds_[1] >= 0)
HITCBC 208   1986 ::close(pipe_fds_[1]); 208   1988 ::close(pipe_fds_[1]);
HITCBC 209   3972 } 209   3976 }
210   210  
211   inline void 211   inline void
HITCBC 212   1986 select_scheduler::shutdown() 212   1988 select_scheduler::shutdown()
213   { 213   {
HITCBC 214   1986 shutdown_drain(); 214   1988 shutdown_drain();
215   215  
HITCBC 216   1986 if (pipe_fds_[1] >= 0) 216   1988 if (pipe_fds_[1] >= 0)
HITCBC 217   1986 interrupt_reactor(); 217   1988 interrupt_reactor();
HITCBC 218   1986 } 218   1988 }
219   219  
220   inline std::error_code 220   inline std::error_code
HITCBC 221   9982 select_scheduler::register_descriptor( 221   9857 select_scheduler::register_descriptor(
222   int fd, reactor_descriptor_state* desc) const 222   int fd, reactor_descriptor_state* desc) const
223   { 223   {
HITCBC 224   9982 if (fd < 0 || fd >= FD_SETSIZE) 224   9857 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   9981 if (desc->mutex.enabled() != reactor_io_locking_) 230   9856 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   9981 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 233   9856 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 234   9981 desc->registered_events = reactor_event_read | reactor_event_write; 234   9856 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 235   9981 desc->unpollable = false; // the state is reused across adoptions 235   9856 desc->unpollable = false; // the state is reused across adoptions
HITCBC 236   9981 desc->fd = fd; 236   9856 desc->fd = fd;
HITCBC 237   9981 desc->scheduler_ = this; 237   9856 desc->scheduler_ = this;
HITCBC 238   9981 desc->ready_events_.store(0, std::memory_order_release); 238   9856 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   9981 desc->read_ready = false; 241   9856 desc->read_ready = false;
HITCBC 242   9981 desc->write_ready = false; 242   9856 desc->write_ready = false;
HITCBC 243   9981 } 243   9856 }
244   244  
245   { 245   {
HITCBC 246   9981 mutex_type::scoped_lock lock(mutex_); 246   9856 mutex_type::scoped_lock lock(mutex_);
247   try 247   try
248   { 248   {
HITCBC 249   9981 registered_descs_[fd] = desc; 249   9856 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   9980 if (fd > max_fd_) 255   9855 if (fd > max_fd_)
HITCBC 256   9504 max_fd_ = fd; 256   9418 max_fd_ = fd;
HITCBC 257   9981 } 257   9856 }
258   258  
HITCBC 259   9980 interrupt_reactor(); 259   9855 interrupt_reactor();
HITCBC 260   9980 return {}; 260   9855 return {};
261   } 261   }
262   262  
263   inline void 263   inline void
HITCBC 264   9707 select_scheduler::deregister_descriptor(int fd) const 264   9582 select_scheduler::deregister_descriptor(int fd) const
265   { 265   {
HITCBC 266   9707 mutex_type::scoped_lock lock(mutex_); 266   9582 mutex_type::scoped_lock lock(mutex_);
267   267  
HITCBC 268   9707 auto it = registered_descs_.find(fd); 268   9582 auto it = registered_descs_.find(fd);
HITCBC 269   9707 if (it == registered_descs_.end()) 269   9582 if (it == registered_descs_.end())
MISUBC 270   ✗ return; 270   ✗ return;
271   271  
HITCBC 272   9707 registered_descs_.erase(it); 272   9582 registered_descs_.erase(it);
273   273  
HITCBC 274   9707 if (fd == max_fd_) 274   9582 if (fd == max_fd_)
275   { 275   {
HITCBC 276   7870 max_fd_ = pipe_fds_[0]; 276   7855 max_fd_ = pipe_fds_[0];
HITCBC 277   13142 for (auto& [registered_fd, state] : registered_descs_) 277   13120 for (auto& [registered_fd, state] : registered_descs_)
278   { 278   {
HITCBC 279   5272 if (registered_fd > max_fd_) 279   5265 if (registered_fd > max_fd_)
HITCBC 280   5009 max_fd_ = registered_fd; 280   5018 max_fd_ = registered_fd;
281   } 281   }
282   } 282   }
HITCBC 283   9707 } 283   9582 }
284   284  
285   inline void 285   inline void
HITCBC 286   6807 select_scheduler::notify_reactor() const 286   6881 select_scheduler::notify_reactor() const
287   { 287   {
HITCBC 288   6807 interrupt_reactor(); 288   6881 interrupt_reactor();
HITCBC 289   6807 } 289   6881 }
290   290  
291   inline void 291   inline void
HITCBC 292   25538 select_scheduler::interrupt_reactor() const 292   25495 select_scheduler::interrupt_reactor() const
293   { 293   {
HITCBC 294   25538 char byte = 1; 294   25495 char byte = 1;
HITCBC 295   25538 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 295   25495 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 296   25538 } 296   25495 }
297   297  
298   inline long 298   inline long
HITCBC 299   12653 select_scheduler::calculate_timeout(long requested_timeout_us) const 299   14111 select_scheduler::calculate_timeout(long requested_timeout_us) const
300   { 300   {
HITCBC 301   12653 if (requested_timeout_us == 0) 301   14111 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   12653 auto* tsvc = timers(); 304   14111 auto* tsvc = timers();
HITCBC 305   12653 if (!tsvc) 305   14111 if (!tsvc)
HITCBC 306   6012 return requested_timeout_us; 306   7214 return requested_timeout_us;
HITCBC 307   6641 auto nearest = tsvc->nearest_expiry(); 307   6897 auto nearest = tsvc->nearest_expiry();
HITCBC 308   6641 if (nearest == timer_service::time_point::max()) 308   6897 if (nearest == timer_service::time_point::max())
HITCBC 309   142 return requested_timeout_us; 309   145 return requested_timeout_us;
310   310  
HITCBC 311   6499 auto now = std::chrono::steady_clock::now(); 311   6752 auto now = std::chrono::steady_clock::now();
HITCBC 312   6499 if (nearest <= now) 312   6752 if (nearest <= now)
HITCBC 313   108 return 0; 313   100 return 0;
314   314  
315   auto timer_timeout_us = 315   auto timer_timeout_us =
HITCBC 316   6391 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 316   6652 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 317   6391 .count(); 317   6652 .count();
318   318  
HITCBC 319   6391 constexpr auto long_max = 319   6652 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   6391 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 322   6652 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 323   6391 static_cast<long long>(0)), 323   6652 static_cast<long long>(0)),
HITCBC 324   6391 long_max); 324   6652 long_max);
325   325  
HITCBC 326   6391 if (requested_timeout_us < 0) 326   6652 if (requested_timeout_us < 0)
HITCBC 327   6385 return static_cast<long>(capped_timer_us); 327   6646 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   138879 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us) 335   77736 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   138879 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 338   77736 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   138879 int snapshot_count = 0; 357   77736 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   138879 if (!lock.owns_lock()) 361   77736 if (!lock.owns_lock())
HITCBC 362   126223 lock.lock(); 362   63624 lock.lock();
363   363  
HITCBC 364   385740 for (auto& [fd, desc] : registered_descs_) 364   232853 for (auto& [fd, desc] : registered_descs_)
365   { 365   {
HITCBC 366   246861 if (snapshot_count < FD_SETSIZE) 366   155117 if (snapshot_count < FD_SETSIZE)
367   { 367   {
HITCBC 368   246861 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 368   155117 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 369   246861 snapshot[snapshot_count].fd = fd; 369   155117 snapshot[snapshot_count].fd = fd;
HITCBC 370   246861 snapshot[snapshot_count].desc = desc; 370   155117 snapshot[snapshot_count].desc = desc;
HITCBC 371   246861 snapshot[snapshot_count].want = 371   155117 snapshot[snapshot_count].want =
HITCBC 372   246861 ((desc->read_op || desc->wait_read_op) ? reactor_event_read 372   155117 ((desc->read_op || desc->wait_read_op) ? reactor_event_read
HITCBC 373   246861 : 0) | 373   155117 : 0) |
HITCBC 374   246487 ((desc->write_op || desc->connect_op || desc->wait_write_op) 374   154748 ((desc->write_op || desc->connect_op || desc->wait_write_op)
HITCBC 375   493348 ? reactor_event_write 375   309865 ? reactor_event_write
HITCBC 376   246861 : 0) | 376   155117 : 0) |
HITCBC 377   246861 (desc->wait_error_op ? reactor_event_error : 0); 377   155117 (desc->wait_error_op ? reactor_event_error : 0);
HITCBC 378   246861 ++snapshot_count; 378   155117 ++snapshot_count;
HITCBC 379   246861 } 379   155117 }
380   } 380   }
381   381  
HITCBC 382   138879 if (lock.owns_lock()) 382   77736 if (lock.owns_lock())
HITCBC 383   138878 lock.unlock(); 383   77736 lock.unlock();
384   384  
HITCBC 385   138879 task_cleanup on_exit{this, &lock, ctx}; 385   77736 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   2360943 FD_ZERO(&read_fds); 388   1321512 FD_ZERO(&read_fds);
HITCBC 389   2360943 FD_ZERO(&write_fds); 389   1321512 FD_ZERO(&write_fds);
HITCBC 390   2360943 FD_ZERO(&except_fds); 390   1321512 FD_ZERO(&except_fds);
391   391  
HITCBC 392   138879 FD_SET(pipe_fds_[0], &read_fds); 392   77736 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 393   138879 int nfds = pipe_fds_[0]; 393   77736 int nfds = pipe_fds_[0];
394   394  
HITCBC 395   385740 for (int i = 0; i < snapshot_count; ++i) 395   232853 for (int i = 0; i < snapshot_count; ++i)
396   { 396   {
HITCBC 397   246861 int fd = snapshot[i].fd; 397   155117 int fd = snapshot[i].fd;
HITCBC 398   246861 if (snapshot[i].want & reactor_event_read) 398   155117 if (snapshot[i].want & reactor_event_read)
HITCBC 399   111691 FD_SET(fd, &read_fds); 399   62306 FD_SET(fd, &read_fds);
HITCBC 400   246861 if (snapshot[i].want & reactor_event_write) 400   155117 if (snapshot[i].want & reactor_event_write)
HITCBC 401   3019 FD_SET(fd, &write_fds); 401   3045 FD_SET(fd, &write_fds);
HITCBC 402   246861 if (snapshot[i].want != 0) 402   155117 if (snapshot[i].want != 0)
HITCBC 403   114905 FD_SET(fd, &except_fds); 403   65546 FD_SET(fd, &except_fds);
HITCBC 404   246861 if (fd > nfds) 404   155117 if (fd > nfds)
HITCBC 405   136878 nfds = fd; 405   75403 nfds = fd;
406   } 406   }
407   407  
408   struct timeval tv; 408   struct timeval tv;
HITCBC 409   138879 struct timeval* tv_ptr = nullptr; 409   77736 struct timeval* tv_ptr = nullptr;
HITCBC 410   138879 if (effective_timeout_us >= 0) 410   77736 if (effective_timeout_us >= 0)
411   { 411   {
HITCBC 412   133302 tv.tv_sec = effective_timeout_us / 1000000; 412   71252 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 413   133302 tv.tv_usec = effective_timeout_us % 1000000; 413   71252 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 414   133302 tv_ptr = &tv; 414   71252 tv_ptr = &tv;
415   } 415   }
416   416  
HITCBC 417   138879 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 417   77736 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   138879 if (ready < 0) 425   77736 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   138878 if (auto* tsvc = timers()) 433   77735 if (auto* tsvc = timers())
HITCBC 434   28047 tsvc->process_expired(); 434   18618 tsvc->process_expired();
435   435  
HITCBC 436   138878 ready_queue local_ops; 436   77735 ready_queue local_ops;
437   437  
HITCBC 438   138878 if (ready > 0) 438   77735 if (ready > 0)
439   { 439   {
HITCBC 440   13026 if (FD_ISSET(pipe_fds_[0], &read_fds)) 440   12756 if (FD_ISSET(pipe_fds_[0], &read_fds))
441   { 441   {
442   char buf[256]; 442   char buf[256];
HITCBC 443   22394 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 443   20655 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
444   { 444   {
445   } 445   }
446   } 446   }
447   447  
HITCBC 448   93736 for (int i = 0; i < snapshot_count; ++i) 448   81297 for (int i = 0; i < snapshot_count; ++i)
449   { 449   {
HITCBC 450   80710 int fd = snapshot[i].fd; 450   68541 int fd = snapshot[i].fd;
HITCBC 451   80710 reactor_descriptor_state* desc = snapshot[i].desc; 451   68541 reactor_descriptor_state* desc = snapshot[i].desc;
452   452  
HITCBC 453   80710 std::uint32_t flags = 0; 453   68541 std::uint32_t flags = 0;
HITCBC 454   80710 if (FD_ISSET(fd, &read_fds)) 454   68541 if (FD_ISSET(fd, &read_fds))
HITCBC 455   4554 flags |= reactor_event_read; 455   5467 flags |= reactor_event_read;
HITCBC 456   80710 if (FD_ISSET(fd, &write_fds)) 456   68541 if (FD_ISSET(fd, &write_fds))
HITCBC 457   2735 flags |= reactor_event_write; 457   2765 flags |= reactor_event_write;
HITCBC 458   80710 if (FD_ISSET(fd, &except_fds)) 458   68541 if (FD_ISSET(fd, &except_fds))
HITCBC 459   10 flags |= reactor_event_error; 459   16 flags |= reactor_event_error;
460   460  
HITCBC 461   80710 if (flags == 0) 461   68541 if (flags == 0)
HITCBC 462   73419 continue; 462   60307 continue;
463   463  
HITCBC 464   7291 desc->add_ready_events(flags); 464   8234 desc->add_ready_events(flags);
465   465  
HITCBC 466   7291 bool expected = false; 466   8234 bool expected = false;
HITCBC 467   7291 if (desc->is_enqueued_.compare_exchange_strong( 467   8234 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   6226 local_ops.push(desc); 471   6419 local_ops.push(desc);
472   } 472   }
473   } 473   }
474   } 474   }
475   475  
HITCBC 476   138878 lock.lock(); 476   77735 lock.lock();
477   477  
HITCBC 478   138878 completed_ops_.splice(local_ops); 478   77735 completed_ops_.splice(local_ops);
HITCBC 479   138879 } 479   77736 }
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