. /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   2783 ensure_write_registered(int, reactor_descriptor_state*) const noexcept 118   2849 ensure_write_registered(int, reactor_descriptor_state*) const noexcept
119   { 119   {
HITCBC 120   2783 return {}; 120   2849 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   492 void notify_reparked() const override 148   423 void notify_reparked() const override
149   { 149   {
HITCBC 150   492 interrupt_reactor(); 150   423 interrupt_reactor();
HITCBC 151   492 } 151   423 }
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   1993 inline select_scheduler::select_scheduler(capy::execution_context&, int)
HITCBC 168   1993 : pipe_fds_{-1, -1} 168   1993 : pipe_fds_{-1, -1}
HITCBC 169   1993 , max_fd_(-1) 169   1993 , max_fd_(-1)
170   { 170   {
HITCBC 171   1993 if (::pipe(pipe_fds_) < 0) 171   1993 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   5967 for (int i = 0; i < 2; ++i)
175   { 175   {
HITCBC 176   3981 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 176   3981 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 177   3981 if (flags == -1) 177   3981 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   3979 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   3977 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   1986 completed_ops_.push(&task_op_);
HITCBC 201   2007 } 201   2007 }
202   202  
HITCBC 203   3972 inline select_scheduler::~select_scheduler() 203   3972 inline select_scheduler::~select_scheduler()
204   { 204   {
HITCBC 205   1986 if (pipe_fds_[0] >= 0) 205   1986 if (pipe_fds_[0] >= 0)
HITCBC 206   1986 ::close(pipe_fds_[0]); 206   1986 ::close(pipe_fds_[0]);
HITCBC 207   1986 if (pipe_fds_[1] >= 0) 207   1986 if (pipe_fds_[1] >= 0)
HITCBC 208   1986 ::close(pipe_fds_[1]); 208   1986 ::close(pipe_fds_[1]);
HITCBC 209   3972 } 209   3972 }
210   210  
211   inline void 211   inline void
HITCBC 212   1986 select_scheduler::shutdown() 212   1986 select_scheduler::shutdown()
213   { 213   {
HITCBC 214   1986 shutdown_drain(); 214   1986 shutdown_drain();
215   215  
HITCBC 216   1986 if (pipe_fds_[1] >= 0) 216   1986 if (pipe_fds_[1] >= 0)
HITCBC 217   1986 interrupt_reactor(); 217   1986 interrupt_reactor();
HITCBC 218   1986 } 218   1986 }
219   219  
220   inline std::error_code 220   inline std::error_code
HITCBC 221   9972 select_scheduler::register_descriptor( 221   10138 select_scheduler::register_descriptor(
222   int fd, reactor_descriptor_state* desc) const 222   int fd, reactor_descriptor_state* desc) const
223   { 223   {
HITCBC 224   9972 if (fd < 0 || fd >= FD_SETSIZE) 224   10138 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   9971 if (desc->mutex.enabled() != reactor_io_locking_) 230   10137 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   9971 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 233   10137 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 234   9971 desc->registered_events = reactor_event_read | reactor_event_write; 234   10137 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 235   9971 desc->unpollable = false; // the state is reused across adoptions 235   10137 desc->unpollable = false; // the state is reused across adoptions
HITCBC 236   9971 desc->fd = fd; 236   10137 desc->fd = fd;
HITCBC 237   9971 desc->scheduler_ = this; 237   10137 desc->scheduler_ = this;
HITCBC 238   9971 desc->ready_events_.store(0, std::memory_order_release); 238   10137 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   9971 desc->read_ready = false; 241   10137 desc->read_ready = false;
HITCBC 242   9971 desc->write_ready = false; 242   10137 desc->write_ready = false;
HITCBC 243   9971 } 243   10137 }
244   244  
245   { 245   {
HITCBC 246   9971 mutex_type::scoped_lock lock(mutex_); 246   10137 mutex_type::scoped_lock lock(mutex_);
247   try 247   try
248   { 248   {
HITCBC 249   9971 registered_descs_[fd] = desc; 249   10137 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   9970 if (fd > max_fd_) 255   10136 if (fd > max_fd_)
HITCBC 256   9476 max_fd_ = fd; 256   9629 max_fd_ = fd;
HITCBC 257   9971 } 257   10137 }
258   258  
HITCBC 259   9970 interrupt_reactor(); 259   10136 interrupt_reactor();
HITCBC 260   9970 return {}; 260   10136 return {};
261   } 261   }
262   262  
263   inline void 263   inline void
HITCBC 264   9697 select_scheduler::deregister_descriptor(int fd) const 264   9863 select_scheduler::deregister_descriptor(int fd) const
265   { 265   {
HITCBC 266   9697 mutex_type::scoped_lock lock(mutex_); 266   9863 mutex_type::scoped_lock lock(mutex_);
267   267  
HITCBC 268   9697 auto it = registered_descs_.find(fd); 268   9863 auto it = registered_descs_.find(fd);
HITCBC 269   9697 if (it == registered_descs_.end()) 269   9863 if (it == registered_descs_.end())
MISUBC 270   ✗ return; 270   ✗ return;
271   271  
HITCBC 272   9697 registered_descs_.erase(it); 272   9863 registered_descs_.erase(it);
273   273  
HITCBC 274   9697 if (fd == max_fd_) 274   9863 if (fd == max_fd_)
275   { 275   {
HITCBC 276   7860 max_fd_ = pipe_fds_[0]; 276   8028 max_fd_ = pipe_fds_[0];
HITCBC 277   13135 for (auto& [registered_fd, state] : registered_descs_) 277   13472 for (auto& [registered_fd, state] : registered_descs_)
278   { 278   {
HITCBC 279   5275 if (registered_fd > max_fd_) 279   5444 if (registered_fd > max_fd_)
HITCBC 280   5026 max_fd_ = registered_fd; 280   5193 max_fd_ = registered_fd;
281   } 281   }
282   } 282   }
HITCBC 283   9697 } 283   9863 }
284   284  
285   inline void 285   inline void
HITCBC 286   6857 select_scheduler::notify_reactor() const 286   6981 select_scheduler::notify_reactor() const
287   { 287   {
HITCBC 288   6857 interrupt_reactor(); 288   6981 interrupt_reactor();
HITCBC 289   6857 } 289   6981 }
290   290  
291   inline void 291   inline void
HITCBC 292   25835 select_scheduler::interrupt_reactor() const 292   26042 select_scheduler::interrupt_reactor() const
293   { 293   {
HITCBC 294   25835 char byte = 1; 294   26042 char byte = 1;
HITCBC 295   25835 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 295   26042 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 296   25835 } 296   26042 }
297   297  
298   inline long 298   inline long
HITCBC 299   97628 select_scheduler::calculate_timeout(long requested_timeout_us) const 299   12240 select_scheduler::calculate_timeout(long requested_timeout_us) const
300   { 300   {
HITCBC 301   97628 if (requested_timeout_us == 0) 301   12240 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   97628 auto* tsvc = timers(); 304   12240 auto* tsvc = timers();
HITCBC 305   97628 if (!tsvc) 305   12240 if (!tsvc)
HITCBC 306   90869 return requested_timeout_us; 306   5273 return requested_timeout_us;
HITCBC 307   6759 auto nearest = tsvc->nearest_expiry(); 307   6967 auto nearest = tsvc->nearest_expiry();
HITCBC 308   6759 if (nearest == timer_service::time_point::max()) 308   6967 if (nearest == timer_service::time_point::max())
HITCBC 309   141 return requested_timeout_us; 309   137 return requested_timeout_us;
310   310  
HITCBC 311   6618 auto now = std::chrono::steady_clock::now(); 311   6830 auto now = std::chrono::steady_clock::now();
HITCBC 312   6618 if (nearest <= now) 312   6830 if (nearest <= now)
HITCBC 313   64 return 0; 313   36 return 0;
314   314  
315   auto timer_timeout_us = 315   auto timer_timeout_us =
HITCBC 316   6554 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 316   6794 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 317   6554 .count(); 317   6794 .count();
318   318  
HITCBC 319   6554 constexpr auto long_max = 319   6794 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   6554 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 322   6794 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 323   6554 static_cast<long long>(0)), 323   6794 static_cast<long long>(0)),
HITCBC 324   6554 long_max); 324   6794 long_max);
325   325  
HITCBC 326   6554 if (requested_timeout_us < 0) 326   6794 if (requested_timeout_us < 0)
HITCBC 327   6548 return static_cast<long>(capped_timer_us); 327   6788 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   225435 select_scheduler::run_task(lock_type& lock, context_type& ctx, long timeout_us) 335   138733 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   225435 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 338   138733 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   225435 int snapshot_count = 0; 357   138733 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   225435 if (!lock.owns_lock()) 361   138733 if (!lock.owns_lock())
HITCBC 362   127804 lock.lock(); 362   126490 lock.lock();
363   363  
HITCBC 364   564752 for (auto& [fd, desc] : registered_descs_) 364   385962 for (auto& [fd, desc] : registered_descs_)
365   { 365   {
HITCBC 366   339317 if (snapshot_count < FD_SETSIZE) 366   247229 if (snapshot_count < FD_SETSIZE)
367   { 367   {
HITCBC 368   339317 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 368   247229 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 369   339317 snapshot[snapshot_count].fd = fd; 369   247229 snapshot[snapshot_count].fd = fd;
HITCBC 370   339317 snapshot[snapshot_count].desc = desc; 370   247229 snapshot[snapshot_count].desc = desc;
HITCBC 371   339317 snapshot[snapshot_count].want = 371   247229 snapshot[snapshot_count].want =
HITCBC 372   339317 ((desc->read_op || desc->wait_read_op) ? reactor_event_read 372   247229 ((desc->read_op || desc->wait_read_op) ? reactor_event_read
HITCBC 373   339317 : 0) | 373   247229 : 0) |
HITCBC 374   338943 ((desc->write_op || desc->connect_op || desc->wait_write_op) 374   246855 ((desc->write_op || desc->connect_op || desc->wait_write_op)
HITCBC 375   678260 ? reactor_event_write 375   494084 ? reactor_event_write
HITCBC 376   339317 : 0) | 376   247229 : 0) |
HITCBC 377   339317 (desc->wait_error_op ? reactor_event_error : 0); 377   247229 (desc->wait_error_op ? reactor_event_error : 0);
HITCBC 378   339317 ++snapshot_count; 378   247229 ++snapshot_count;
HITCBC 379   339317 } 379   247229 }
380   } 380   }
381   381  
HITCBC 382   225435 if (lock.owns_lock()) 382   138733 if (lock.owns_lock())
HITCBC 383   225434 lock.unlock(); 383   138732 lock.unlock();
384   384  
HITCBC 385   225435 task_cleanup on_exit{this, &lock, ctx}; 385   138733 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   3832395 FD_ZERO(&read_fds); 388   2358461 FD_ZERO(&read_fds);
HITCBC 389   3832395 FD_ZERO(&write_fds); 389   2358461 FD_ZERO(&write_fds);
HITCBC 390   3832395 FD_ZERO(&except_fds); 390   2358461 FD_ZERO(&except_fds);
391   391  
HITCBC 392   225435 FD_SET(pipe_fds_[0], &read_fds); 392   138733 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 393   225435 int nfds = pipe_fds_[0]; 393   138733 int nfds = pipe_fds_[0];
394   394  
HITCBC 395   564752 for (int i = 0; i < snapshot_count; ++i) 395   385962 for (int i = 0; i < snapshot_count; ++i)
396   { 396   {
HITCBC 397   339317 int fd = snapshot[i].fd; 397   247229 int fd = snapshot[i].fd;
HITCBC 398   339317 if (snapshot[i].want & reactor_event_read) 398   247229 if (snapshot[i].want & reactor_event_read)
HITCBC 399   196516 FD_SET(fd, &read_fds); 399   111284 FD_SET(fd, &read_fds);
HITCBC 400   339317 if (snapshot[i].want & reactor_event_write) 400   247229 if (snapshot[i].want & reactor_event_write)
HITCBC 401   3047 FD_SET(fd, &write_fds); 401   3113 FD_SET(fd, &write_fds);
HITCBC 402   339317 if (snapshot[i].want != 0) 402   247229 if (snapshot[i].want != 0)
HITCBC 403   199758 FD_SET(fd, &except_fds); 403   114592 FD_SET(fd, &except_fds);
HITCBC 404   339317 if (fd > nfds) 404   247229 if (fd > nfds)
HITCBC 405   223329 nfds = fd; 405   136816 nfds = fd;
406   } 406   }
407   407  
408   struct timeval tv; 408   struct timeval tv;
HITCBC 409   225435 struct timeval* tv_ptr = nullptr; 409   138733 struct timeval* tv_ptr = nullptr;
HITCBC 410   225435 if (effective_timeout_us >= 0) 410   138733 if (effective_timeout_us >= 0)
411   { 411   {
HITCBC 412   135088 tv.tv_sec = effective_timeout_us / 1000000; 412   133993 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 413   135088 tv.tv_usec = effective_timeout_us % 1000000; 413   133993 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 414   135088 tv_ptr = &tv; 414   133993 tv_ptr = &tv;
415   } 415   }
416   416  
HITCBC 417   225435 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 417   138733 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   225435 if (ready < 0) 425   138733 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   225434 if (auto* tsvc = timers()) 433   138732 if (auto* tsvc = timers())
HITCBC 434   30055 tsvc->process_expired(); 434   28653 tsvc->process_expired();
435   435  
HITCBC 436   225434 ready_queue local_ops; 436   138732 ready_queue local_ops;
437   437  
HITCBC 438   225434 if (ready > 0) 438   138732 if (ready > 0)
439   { 439   {
HITCBC 440   97972 if (FD_ISSET(pipe_fds_[0], &read_fds)) 440   12456 if (FD_ISSET(pipe_fds_[0], &read_fds))
441   { 441   {
442   char buf[256]; 442   char buf[256];
HITCBC 443   22792 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 443   23001 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
444   { 444   {
445   } 445   }
446   } 446   }
447   447  
HITCBC 448   266521 for (int i = 0; i < snapshot_count; ++i) 448   92762 for (int i = 0; i < snapshot_count; ++i)
449   { 449   {
HITCBC 450   168549 int fd = snapshot[i].fd; 450   80306 int fd = snapshot[i].fd;
HITCBC 451   168549 reactor_descriptor_state* desc = snapshot[i].desc; 451   80306 reactor_descriptor_state* desc = snapshot[i].desc;
452   452  
HITCBC 453   168549 std::uint32_t flags = 0; 453   80306 std::uint32_t flags = 0;
HITCBC 454   168549 if (FD_ISSET(fd, &read_fds)) 454   80306 if (FD_ISSET(fd, &read_fds))
HITCBC 455   89590 flags |= reactor_event_read; 455   3822 flags |= reactor_event_read;
HITCBC 456   168549 if (FD_ISSET(fd, &write_fds)) 456   80306 if (FD_ISSET(fd, &write_fds))
HITCBC 457   2763 flags |= reactor_event_write; 457   2829 flags |= reactor_event_write;
HITCBC 458   168549 if (FD_ISSET(fd, &except_fds)) 458   80306 if (FD_ISSET(fd, &except_fds))
HITCBC 459   11 flags |= reactor_event_error; 459   10 flags |= reactor_event_error;
460   460  
HITCBC 461   168549 if (flags == 0) 461   80306 if (flags == 0)
HITCBC 462   76194 continue; 462   73653 continue;
463   463  
HITCBC 464   92355 desc->add_ready_events(flags); 464   6653 desc->add_ready_events(flags);
465   465  
HITCBC 466   92355 bool expected = false; 466   6653 bool expected = false;
HITCBC 467   92355 if (desc->is_enqueued_.compare_exchange_strong( 467   6653 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   6390 local_ops.push(desc); 471   6441 local_ops.push(desc);
472   } 472   }
473   } 473   }
474   } 474   }
475   475  
HITCBC 476   225434 lock.lock(); 476   138732 lock.lock();
477   477  
HITCBC 478   225434 completed_ops_.splice(local_ops); 478   138732 completed_ops_.splice(local_ops);
HITCBC 479   225435 } 479   138733 }
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