. /include/boost/corosio /native /detail /select /select_scheduler.hpp
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1   // 1   //
2   // Copyright (c) 2026 Steve Gerbino 2   // Copyright (c) 2026 Steve Gerbino
3   // Copyright (c) 2026 Michael Vandeberg 3   // Copyright (c) 2026 Michael Vandeberg
4   // 4   //
5   // Distributed under the Boost Software License, Version 1.0. (See accompanying 5   // Distributed under the Boost Software License, Version 1.0. (See accompanying
6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7   // 7   //
8   // Official repository: https://github.com/cppalliance/corosio 8   // Official repository: https://github.com/cppalliance/corosio
9   // 9   //
10   10  
11   #ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 11   #ifndef BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
12   #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 12   #define BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP
13   13  
14   #include <boost/corosio/detail/platform.hpp> 14   #include <boost/corosio/detail/platform.hpp>
15   15  
16   #if BOOST_COROSIO_HAS_SELECT 16   #if BOOST_COROSIO_HAS_SELECT
17   17  
18   #include <boost/corosio/detail/config.hpp> 18   #include <boost/corosio/detail/config.hpp>
19   #include <boost/capy/ex/execution_context.hpp> 19   #include <boost/capy/ex/execution_context.hpp>
20   20  
21   #include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp> 21   #include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp>
22   #include <boost/corosio/native/detail/reactor/reactor_signal_pipe.hpp> 22   #include <boost/corosio/native/detail/reactor/reactor_signal_pipe.hpp>
23   23  
24   #include <boost/corosio/native/detail/select/select_traits.hpp> 24   #include <boost/corosio/native/detail/select/select_traits.hpp>
25   #include <boost/corosio/detail/timer_service.hpp> 25   #include <boost/corosio/detail/timer_service.hpp>
26   #include <boost/corosio/native/detail/make_err.hpp> 26   #include <boost/corosio/native/detail/make_err.hpp>
27   #include <boost/corosio/native/detail/posix/posix_resolver_service.hpp> 27   #include <boost/corosio/native/detail/posix/posix_resolver_service.hpp>
28   #include <boost/corosio/native/detail/posix/posix_signal_service.hpp> 28   #include <boost/corosio/native/detail/posix/posix_signal_service.hpp>
29   #include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp> 29   #include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp>
30   #include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp> 30   #include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp>
31   31  
32   #include <boost/corosio/detail/except.hpp> 32   #include <boost/corosio/detail/except.hpp>
33   33  
34   #include <sys/select.h> 34   #include <sys/select.h>
35   #include <unistd.h> 35   #include <unistd.h>
36   #include <errno.h> 36   #include <errno.h>
37   #include <fcntl.h> 37   #include <fcntl.h>
38   38  
39   #include <atomic> 39   #include <atomic>
40   #include <chrono> 40   #include <chrono>
41   #include <cstdint> 41   #include <cstdint>
42   #include <limits> 42   #include <limits>
43   #include <mutex> 43   #include <mutex>
44   #include <new> 44   #include <new>
45   #include <unordered_map> 45   #include <unordered_map>
46   46  
47   namespace boost::corosio::detail { 47   namespace boost::corosio::detail {
48   48  
49   struct select_op; 49   struct select_op;
50   50  
51   /** POSIX scheduler using select() for I/O multiplexing. 51   /** POSIX scheduler using select() for I/O multiplexing.
52   52  
53   This scheduler implements the scheduler interface using the POSIX select() 53   This scheduler implements the scheduler interface using the POSIX select()
54   call for I/O event notification. It inherits the shared reactor threading 54   call for I/O event notification. It inherits the shared reactor threading
55   model from reactor_scheduler: signal state machine, inline completion 55   model from reactor_scheduler: signal state machine, inline completion
56   budget, work counting, and the do_one event loop. 56   budget, work counting, and the do_one event loop.
57   57  
58   The design mirrors epoll_scheduler for behavioral consistency: 58   The design mirrors epoll_scheduler for behavioral consistency:
59   - Same single-reactor thread coordination model 59   - Same single-reactor thread coordination model
60   - Same deferred I/O pattern (reactor marks ready; workers do I/O) 60   - Same deferred I/O pattern (reactor marks ready; workers do I/O)
61   - Same timer integration pattern 61   - Same timer integration pattern
62   62  
63   Known Limitations: 63   Known Limitations:
64   - FD_SETSIZE (~1024) limits maximum concurrent connections 64   - FD_SETSIZE (~1024) limits maximum concurrent connections
65   - O(n) scanning: rebuilds fd_sets each iteration 65   - O(n) scanning: rebuilds fd_sets each iteration
66   - Level-triggered only (no edge-triggered mode) 66   - Level-triggered only (no edge-triggered mode)
67   67  
68   @par Thread Safety 68   @par Thread Safety
69   All public member functions are thread-safe. 69   All public member functions are thread-safe.
70   */ 70   */
71   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler 71   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler
72   { 72   {
73   public: 73   public:
74   /** Construct the scheduler. 74   /** Construct the scheduler.
75   75  
76   Creates a self-pipe for reactor interruption. 76   Creates a self-pipe for reactor interruption.
77   77  
78   @param ctx Reference to the owning execution_context. 78   @param ctx Reference to the owning execution_context.
79   @param concurrency_hint Hint for expected thread count (unused). 79   @param concurrency_hint Hint for expected thread count (unused).
80   */ 80   */
81   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1); 81   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
82   82  
83   /// Destroy the scheduler. 83   /// Destroy the scheduler.
84   ~select_scheduler() override; 84   ~select_scheduler() override;
85   85  
86   select_scheduler(select_scheduler const&) = delete; 86   select_scheduler(select_scheduler const&) = delete;
87   select_scheduler& operator=(select_scheduler const&) = delete; 87   select_scheduler& operator=(select_scheduler const&) = delete;
88   88  
89   /// Shut down the scheduler, draining pending operations. 89   /// Shut down the scheduler, draining pending operations.
90   void shutdown() override; 90   void shutdown() override;
91   91  
92   /** Return the maximum file descriptor value supported. 92   /** Return the maximum file descriptor value supported.
93   93  
94   Returns FD_SETSIZE - 1, the maximum fd value that can be 94   Returns FD_SETSIZE - 1, the maximum fd value that can be
95   monitored by select(). Operations with fd >= FD_SETSIZE 95   monitored by select(). Operations with fd >= FD_SETSIZE
96   will fail with EINVAL. 96   will fail with EINVAL.
97   97  
98   @return The maximum supported file descriptor value. 98   @return The maximum supported file descriptor value.
99   */ 99   */
100   static constexpr int max_fd() noexcept 100   static constexpr int max_fd() noexcept
101   { 101   {
102   return FD_SETSIZE - 1; 102   return FD_SETSIZE - 1;
103   } 103   }
104   104  
105   /** Register a descriptor for persistent monitoring. 105   /** Register a descriptor for persistent monitoring.
106   106  
107   The fd is added to the registered_descs_ map and will be 107   The fd is added to the registered_descs_ map and will be
108   included in subsequent select() calls. The reactor is 108   included in subsequent select() calls. The reactor is
109   interrupted so a blocked select() rebuilds its fd_sets. 109   interrupted so a blocked select() rebuilds its fd_sets.
110   110  
111   @param fd The file descriptor to register. 111   @param fd The file descriptor to register.
112   @param desc Pointer to descriptor state for this fd. 112   @param desc Pointer to descriptor state for this fd.
113   113  
114   @return The error if the fd cannot be tracked, otherwise a 114   @return The error if the fd cannot be tracked, otherwise a
115   default constructed error code. 115   default constructed error code.
116   */ 116   */
117   std::error_code 117   std::error_code
118   register_descriptor(int fd, reactor_descriptor_state* desc) const; 118   register_descriptor(int fd, reactor_descriptor_state* desc) const;
119   119  
120   /** Deregister a persistently registered descriptor. 120   /** Deregister a persistently registered descriptor.
121   121  
122   @param fd The file descriptor to deregister. 122   @param fd The file descriptor to deregister.
123   */ 123   */
124   void deregister_descriptor(int fd) const; 124   void deregister_descriptor(int fd) const;
125   125  
126   /** Interrupt the reactor so it rebuilds its fd_sets. 126   /** Interrupt the reactor so it rebuilds its fd_sets.
127   127  
128   Called when a write, connect, or write-wait op is registered 128   Called when a write, connect, or write-wait op is registered
129   after the reactor's snapshot was taken. Without this, 129   after the reactor's snapshot was taken. Without this,
130   select() may block not watching for writability on the fd. 130   select() may block not watching for writability on the fd.
131   */ 131   */
132   void notify_reactor() const; 132   void notify_reactor() const;
133   133  
134   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp). 134   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp).
135   [[nodiscard]] std::error_code 135   [[nodiscard]] std::error_code
HITCBC 136   41 register_signal_reader(int read_fd) override 136   47 register_signal_reader(int read_fd) override
137   { 137   {
HITCBC 138   41 return register_descriptor(read_fd, signal_pipe_reader_.arm()); 138   47 return register_descriptor(read_fd, signal_pipe_reader_.arm());
139   } 139   }
140   140  
141   private: 141   private:
142   void 142   void
143   run_task(lock_type& lock, context_type* ctx, 143   run_task(lock_type& lock, context_type* ctx,
144   long timeout_us) override; 144   long timeout_us) override;
145   void interrupt_reactor() const override; 145   void interrupt_reactor() const override;
146   long calculate_timeout(long requested_timeout_us) const; 146   long calculate_timeout(long requested_timeout_us) const;
147   147  
148   // Watches the global signal self-pipe's read end (armed lazily by 148   // Watches the global signal self-pipe's read end (armed lazily by
149   // register_signal_reader on the first signal registration). 149   // register_signal_reader on the first signal registration).
150   reactor_signal_pipe_reader signal_pipe_reader_; 150   reactor_signal_pipe_reader signal_pipe_reader_;
151   151  
152   // Self-pipe for interrupting select() 152   // Self-pipe for interrupting select()
153   int pipe_fds_[2]; // [0]=read, [1]=write 153   int pipe_fds_[2]; // [0]=read, [1]=write
154   154  
155   // Per-fd tracking for fd_set building 155   // Per-fd tracking for fd_set building
156   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_; 156   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_;
157   mutable int max_fd_ = -1; 157   mutable int max_fd_ = -1;
158   }; 158   };
159   159  
HITCBC 160   701 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int) 160   788 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 161   701 : pipe_fds_{-1, -1} 161   788 : pipe_fds_{-1, -1}
HITCBC 162   701 , max_fd_(-1) 162   788 , max_fd_(-1)
163   { 163   {
HITCBC 164   701 if (::pipe(pipe_fds_) < 0) 164   788 if (::pipe(pipe_fds_) < 0)
HITGBC 165   ✗ detail::throw_system_error(make_err(errno), "pipe"); 165   1 detail::throw_system_error(make_err(errno), "pipe");
166   166  
HITCBC 167   2103 for (int i = 0; i < 2; ++i) 167   2352 for (int i = 0; i < 2; ++i)
168   { 168   {
HITCBC 169   1402 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 169   1571 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 170   1402 if (flags == -1) 170   1571 if (flags == -1)
171   { 171   {
HITGBC 172   ✗ int errn = errno; 172   2 int errn = errno;
HITGBC 173   ✗ ::close(pipe_fds_[0]); 173   2 ::close(pipe_fds_[0]);
HITGBC 174   ✗ ::close(pipe_fds_[1]); 174   2 ::close(pipe_fds_[1]);
HITGBC 175   ✗ detail::throw_system_error(make_err(errn), "fcntl F_GETFL"); 175   2 detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
176   } 176   }
HITCBC 177   1402 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 177   1569 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
178   { 178   {
HITGBC 179   ✗ int errn = errno; 179   2 int errn = errno;
HITGBC 180   ✗ ::close(pipe_fds_[0]); 180   2 ::close(pipe_fds_[0]);
HITGBC 181   ✗ ::close(pipe_fds_[1]); 181   2 ::close(pipe_fds_[1]);
HITGBC 182   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFL"); 182   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
183   } 183   }
HITCBC 184   1402 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 184   1567 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
185   { 185   {
HITGBC 186   ✗ int errn = errno; 186   2 int errn = errno;
HITGBC 187   ✗ ::close(pipe_fds_[0]); 187   2 ::close(pipe_fds_[0]);
HITGBC 188   ✗ ::close(pipe_fds_[1]); 188   2 ::close(pipe_fds_[1]);
HITGBC 189   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFD"); 189   2 detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
190   } 190   }
191   } 191   }
192   192  
HITCBC 193   701 timer_svc_ = &get_timer_service(ctx, *this); 193   781 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 194   701 timer_svc_->set_on_earliest_changed( 194   781 timer_svc_->set_on_earliest_changed(
HITCBC 195   3479 timer_service::callback(this, [](void* p) { 195   3604 timer_service::callback(this, [](void* p) {
HITCBC 196   2778 static_cast<select_scheduler*>(p)->interrupt_reactor(); 196   2823 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 197   2778 })); 197   2823 }));
198   198  
HITCBC 199   701 get_resolver_service(ctx, *this); 199   781 get_resolver_service(ctx, *this);
HITCBC 200   701 get_signal_service(ctx, *this); 200   781 get_signal_service(ctx, *this);
HITCBC 201   701 get_stream_file_service(ctx, *this); 201   781 get_stream_file_service(ctx, *this);
HITCBC 202   701 get_random_access_file_service(ctx, *this); 202   781 get_random_access_file_service(ctx, *this);
203   203  
HITCBC 204   701 completed_ops_.push(&task_op_); 204   781 completed_ops_.push(&task_op_);
HITCBC 205   701 } 205   802 }
206   206  
HITCBC 207   1402 inline select_scheduler::~select_scheduler() 207   1562 inline select_scheduler::~select_scheduler()
208   { 208   {
HITCBC 209   701 if (pipe_fds_[0] >= 0) 209   781 if (pipe_fds_[0] >= 0)
HITCBC 210   701 ::close(pipe_fds_[0]); 210   781 ::close(pipe_fds_[0]);
HITCBC 211   701 if (pipe_fds_[1] >= 0) 211   781 if (pipe_fds_[1] >= 0)
HITCBC 212   701 ::close(pipe_fds_[1]); 212   781 ::close(pipe_fds_[1]);
HITCBC 213   1402 } 213   1562 }
214   214  
215   inline void 215   inline void
HITCBC 216   701 select_scheduler::shutdown() 216   781 select_scheduler::shutdown()
217   { 217   {
HITCBC 218   701 shutdown_drain(); 218   781 shutdown_drain();
219   219  
HITCBC 220   701 if (pipe_fds_[1] >= 0) 220   781 if (pipe_fds_[1] >= 0)
HITCBC 221   701 interrupt_reactor(); 221   781 interrupt_reactor();
HITCBC 222   701 } 222   781 }
223   223  
224   inline std::error_code 224   inline std::error_code
HITCBC 225   4380 select_scheduler::register_descriptor( 225   4558 select_scheduler::register_descriptor(
226   int fd, reactor_descriptor_state* desc) const 226   int fd, reactor_descriptor_state* desc) const
227   { 227   {
HITCBC 228   4380 if (fd < 0 || fd >= FD_SETSIZE) 228   4558 if (fd < 0 || fd >= FD_SETSIZE)
HITGBC 229   ✗ return make_err(EMFILE); 229   1 return make_err(EMFILE);
230   230  
HITCBC 231   4380 desc->registered_events = reactor_event_read | reactor_event_write; 231   4557 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 232   4380 desc->fd = fd; 232   4557 desc->fd = fd;
HITCBC 233   4380 desc->scheduler_ = this; 233   4557 desc->scheduler_ = this;
HITCBC 234   4380 desc->mutex.set_enabled(reactor_io_locking_); 234   4557 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 235   4380 desc->ready_events_.store(0, std::memory_order_relaxed); 235   4557 desc->ready_events_.store(0, std::memory_order_relaxed);
236   236  
237   { 237   {
HITCBC 238   4380 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 238   4557 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 239   4380 desc->impl_ref_.reset(); 239   4557 desc->impl_ref_.reset();
HITCBC 240   4380 desc->read_ready = false; 240   4557 desc->read_ready = false;
HITCBC 241   4380 desc->write_ready = false; 241   4557 desc->write_ready = false;
HITCBC 242   4380 } 242   4557 }
243   243  
244   { 244   {
HITCBC 245   4380 mutex_type::scoped_lock lock(mutex_); 245   4557 mutex_type::scoped_lock lock(mutex_);
246   try 246   try
247   { 247   {
HITCBC 248   4380 registered_descs_[fd] = desc; 248   4557 registered_descs_[fd] = desc;
249   } 249   }
MISUBC 250   ✗ catch (std::bad_alloc const&) 250   ✗ catch (std::bad_alloc const&)
251   { 251   {
MISUBC 252   ✗ return make_err(ENOMEM); 252   ✗ return make_err(ENOMEM);
MISUBC 253   ✗ } 253   ✗ }
HITCBC 254   4380 if (fd > max_fd_) 254   4557 if (fd > max_fd_)
HITCBC 255   4370 max_fd_ = fd; 255   4542 max_fd_ = fd;
HITCBC 256   4380 } 256   4557 }
257   257  
HITCBC 258   4380 interrupt_reactor(); 258   4557 interrupt_reactor();
HITCBC 259   4380 return {}; 259   4557 return {};
260   } 260   }
261   261  
262   inline void 262   inline void
HITCBC 263   4339 select_scheduler::deregister_descriptor(int fd) const 263   4511 select_scheduler::deregister_descriptor(int fd) const
264   { 264   {
HITCBC 265   4339 mutex_type::scoped_lock lock(mutex_); 265   4511 mutex_type::scoped_lock lock(mutex_);
266   266  
HITCBC 267   4339 auto it = registered_descs_.find(fd); 267   4511 auto it = registered_descs_.find(fd);
HITCBC 268   4339 if (it == registered_descs_.end()) 268   4511 if (it == registered_descs_.end())
MISUBC 269   ✗ return; 269   ✗ return;
270   270  
HITCBC 271   4339 registered_descs_.erase(it); 271   4511 registered_descs_.erase(it);
272   272  
HITCBC 273   4339 if (fd == max_fd_) 273   4511 if (fd == max_fd_)
274   { 274   {
HITCBC 275   4183 max_fd_ = pipe_fds_[0]; 275   4320 max_fd_ = pipe_fds_[0];
HITCBC 276   8057 for (auto& [registered_fd, state] : registered_descs_) 276   8315 for (auto& [registered_fd, state] : registered_descs_)
277   { 277   {
HITCBC 278   3874 if (registered_fd > max_fd_) 278   3995 if (registered_fd > max_fd_)
HITCBC 279   3819 max_fd_ = registered_fd; 279   3908 max_fd_ = registered_fd;
280   } 280   }
281   } 281   }
HITCBC 282   4339 } 282   4511 }
283   283  
284   inline void 284   inline void
HITCBC 285   2023 select_scheduler::notify_reactor() const 285   2082 select_scheduler::notify_reactor() const
286   { 286   {
HITCBC 287   2023 interrupt_reactor(); 287   2082 interrupt_reactor();
HITCBC 288   2023 } 288   2082 }
289   289  
290   inline void 290   inline void
HITCBC 291   10462 select_scheduler::interrupt_reactor() const 291   10890 select_scheduler::interrupt_reactor() const
292   { 292   {
HITCBC 293   10462 char byte = 1; 293   10890 char byte = 1;
HITCBC 294   10462 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 294   10890 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 295   10462 } 295   10890 }
296   296  
297   inline long 297   inline long
HITCBC 298   291399 select_scheduler::calculate_timeout(long requested_timeout_us) const 298   340423 select_scheduler::calculate_timeout(long requested_timeout_us) const
299   { 299   {
HITCBC 300   291399 if (requested_timeout_us == 0) 300   340423 if (requested_timeout_us == 0)
MISUBC 301   ✗ return 0; 301   ✗ return 0;
302   302  
HITCBC 303   291399 auto nearest = timer_svc_->nearest_expiry(); 303   340423 auto nearest = timer_svc_->nearest_expiry();
HITCBC 304   291399 if (nearest == timer_service::time_point::max()) 304   340423 if (nearest == timer_service::time_point::max())
HITCBC 305   595 return requested_timeout_us; 305   656 return requested_timeout_us;
306   306  
HITCBC 307   290804 auto now = std::chrono::steady_clock::now(); 307   339767 auto now = std::chrono::steady_clock::now();
HITCBC 308   290804 if (nearest <= now) 308   339767 if (nearest <= now)
HITCBC 309   796 return 0; 309   557 return 0;
310   310  
311   auto timer_timeout_us = 311   auto timer_timeout_us =
HITCBC 312   290008 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 312   339210 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 313   290008 .count(); 313   339210 .count();
314   314  
HITCBC 315   290008 constexpr auto long_max = 315   339210 constexpr auto long_max =
316   static_cast<long long>((std::numeric_limits<long>::max)()); 316   static_cast<long long>((std::numeric_limits<long>::max)());
317   auto capped_timer_us = 317   auto capped_timer_us =
HITCBC 318   290008 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 318   339210 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 319   290008 static_cast<long long>(0)), 319   339210 static_cast<long long>(0)),
HITCBC 320   290008 long_max); 320   339210 long_max);
321   321  
HITCBC 322   290008 if (requested_timeout_us < 0) 322   339210 if (requested_timeout_us < 0)
HITCBC 323   290008 return static_cast<long>(capped_timer_us); 323   339210 return static_cast<long>(capped_timer_us);
324   324  
325   return static_cast<long>( 325   return static_cast<long>(
MISUBC 326   ✗ (std::min)(static_cast<long long>(requested_timeout_us), 326   ✗ (std::min)(static_cast<long long>(requested_timeout_us),
MISUBC 327   ✗ capped_timer_us)); 327   ✗ capped_timer_us));
328   } 328   }
329   329  
330   inline void 330   inline void
HITCBC 331   313378 select_scheduler::run_task( 331   363119 select_scheduler::run_task(
332   lock_type& lock, context_type* ctx, long timeout_us) 332   lock_type& lock, context_type* ctx, long timeout_us)
333   { 333   {
334   long effective_timeout_us = 334   long effective_timeout_us =
HITCBC 335   313378 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 335   363119 task_interrupted_ ? 0 : calculate_timeout(timeout_us);
336   336  
337   // Snapshot registered descriptors while holding lock. 337   // Snapshot registered descriptors while holding lock.
338   // Record which fds need write monitoring to avoid a hot loop: 338   // Record which fds need write monitoring to avoid a hot loop:
339   // select is level-triggered so writable sockets (nearly always 339   // select is level-triggered so writable sockets (nearly always
340   // writable) would cause select() to return immediately every 340   // writable) would cause select() to return immediately every
341   // iteration if unconditionally added to write_fds. Membership 341   // iteration if unconditionally added to write_fds. Membership
342   // stays opt-in: a parked write wait opts in the same way a 342   // stays opt-in: a parked write wait opts in the same way a
343   // parked write or connect op does. 343   // parked write or connect op does.
344   struct fd_entry 344   struct fd_entry
345   { 345   {
346   int fd; 346   int fd;
347   reactor_descriptor_state* desc; 347   reactor_descriptor_state* desc;
348   bool needs_write; 348   bool needs_write;
349   }; 349   };
350   fd_entry snapshot[FD_SETSIZE]; 350   fd_entry snapshot[FD_SETSIZE];
HITCBC 351   313378 int snapshot_count = 0; 351   363119 int snapshot_count = 0;
352   352  
HITCBC 353   757726 for (auto& [fd, desc] : registered_descs_) 353   911495 for (auto& [fd, desc] : registered_descs_)
354   { 354   {
HITCBC 355   444348 if (snapshot_count < FD_SETSIZE) 355   548376 if (snapshot_count < FD_SETSIZE)
356   { 356   {
HITCBC 357   444348 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 357   548376 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 358   444348 snapshot[snapshot_count].fd = fd; 358   548376 snapshot[snapshot_count].fd = fd;
HITCBC 359   444348 snapshot[snapshot_count].desc = desc; 359   548376 snapshot[snapshot_count].desc = desc;
HITCBC 360   444348 snapshot[snapshot_count].needs_write = 360   548376 snapshot[snapshot_count].needs_write =
HITCBC 361   875952 (desc->write_op || desc->connect_op || 361   1084227 (desc->write_op || desc->connect_op ||
HITCBC 362   431604 desc->wait_write_op); 362   535851 desc->wait_write_op);
HITCBC 363   444348 ++snapshot_count; 363   548376 ++snapshot_count;
HITCBC 364   444348 } 364   548376 }
365   } 365   }
366   366  
HITCBC 367   313378 if (lock.owns_lock()) 367   363119 if (lock.owns_lock())
HITCBC 368   291400 lock.unlock(); 368   340424 lock.unlock();
369   369  
HITCBC 370   313378 task_cleanup on_exit{this, &lock, ctx}; 370   363119 task_cleanup on_exit{this, &lock, ctx};
371   371  
372   fd_set read_fds, write_fds, except_fds; 372   fd_set read_fds, write_fds, except_fds;
HITCBC 373   5327426 FD_ZERO(&read_fds); 373   6173023 FD_ZERO(&read_fds);
HITCBC 374   5327426 FD_ZERO(&write_fds); 374   6173023 FD_ZERO(&write_fds);
HITCBC 375   5327426 FD_ZERO(&except_fds); 375   6173023 FD_ZERO(&except_fds);
376   376  
HITCBC 377   313378 FD_SET(pipe_fds_[0], &read_fds); 377   363119 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 378   313378 int nfds = pipe_fds_[0]; 378   363119 int nfds = pipe_fds_[0];
379   379  
HITCBC 380   757726 for (int i = 0; i < snapshot_count; ++i) 380   911495 for (int i = 0; i < snapshot_count; ++i)
381   { 381   {
HITCBC 382   444348 int fd = snapshot[i].fd; 382   548376 int fd = snapshot[i].fd;
HITCBC 383   444348 FD_SET(fd, &read_fds); 383   548376 FD_SET(fd, &read_fds);
HITCBC 384   444348 if (snapshot[i].needs_write) 384   548376 if (snapshot[i].needs_write)
HITCBC 385   12748 FD_SET(fd, &write_fds); 385   12531 FD_SET(fd, &write_fds);
HITCBC 386   444348 FD_SET(fd, &except_fds); 386   548376 FD_SET(fd, &except_fds);
HITCBC 387   444348 if (fd > nfds) 387   548376 if (fd > nfds)
HITCBC 388   312970 nfds = fd; 388   362663 nfds = fd;
389   } 389   }
390   390  
391   struct timeval tv; 391   struct timeval tv;
HITCBC 392   313378 struct timeval* tv_ptr = nullptr; 392   363119 struct timeval* tv_ptr = nullptr;
HITCBC 393   313378 if (effective_timeout_us >= 0) 393   363119 if (effective_timeout_us >= 0)
394   { 394   {
HITCBC 395   312787 tv.tv_sec = effective_timeout_us / 1000000; 395   362467 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 396   312787 tv.tv_usec = effective_timeout_us % 1000000; 396   362467 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 397   312787 tv_ptr = &tv; 397   362467 tv_ptr = &tv;
398   } 398   }
399   399  
HITCBC 400   313378 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 400   363119 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
401   401  
402   // EINTR: signal interrupted select(), just retry. 402   // EINTR: signal interrupted select(), just retry.
403   // EBADF: an fd was closed between snapshot and select(); retry 403   // EBADF: an fd was closed between snapshot and select(); retry
404   // with a fresh snapshot from registered_descs_. 404   // with a fresh snapshot from registered_descs_.
  405 + // Both fall through with no ready descriptors rather than
  406 + // returning: the caller handed this function an owned lock that
  407 + // only the epilogue below re-acquires.
HITCBC 405   313378 if (ready < 0) 408   363119 if (ready < 0)
406   { 409   {
HITGBC 407 - ✗ if (errno == EINTR || errno == EBADF) 410 + 3 if (errno != EINTR && errno != EBADF)
HITGBC 408 - ✗ return; 411 + 1 detail::throw_system_error(make_err(errno), "select");
HITGBC 409 - ✗ detail::throw_system_error(make_err(errno), "select"); 412 + 2 ready = 0;
410   } 413   }
411   414  
412   // Process timers outside the lock 415   // Process timers outside the lock
HITCBC 413   313378 timer_svc_->process_expired(); 416   363118 timer_svc_->process_expired();
414   417  
HITCBC 415   313378 ready_queue local_ops; 418   363118 ready_queue local_ops;
416   419  
HITCBC 417   313378 if (ready > 0) 420   363118 if (ready > 0)
418   { 421   {
HITCBC 419   298278 if (FD_ISSET(pipe_fds_[0], &read_fds)) 422   347714 if (FD_ISSET(pipe_fds_[0], &read_fds))
420   { 423   {
421   char buf[256]; 424   char buf[256];
HITCBC 422   9208 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 425   9554 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
423   { 426   {
424   } 427   }
425   } 428   }
426   429  
HITCBC 427   697252 for (int i = 0; i < snapshot_count; ++i) 430   852306 for (int i = 0; i < snapshot_count; ++i)
428   { 431   {
HITCBC 429   398974 int fd = snapshot[i].fd; 432   504592 int fd = snapshot[i].fd;
HITCBC 430   398974 reactor_descriptor_state* desc = snapshot[i].desc; 433   504592 reactor_descriptor_state* desc = snapshot[i].desc;
431   434  
HITCBC 432   398974 std::uint32_t flags = 0; 435   504592 std::uint32_t flags = 0;
HITCBC 433   398974 if (FD_ISSET(fd, &read_fds)) 436   504592 if (FD_ISSET(fd, &read_fds))
HITCBC 434   295883 flags |= reactor_event_read; 437   345255 flags |= reactor_event_read;
HITCBC 435   398974 if (FD_ISSET(fd, &write_fds)) 438   504592 if (FD_ISSET(fd, &write_fds))
HITCBC 436   2018 flags |= reactor_event_write; 439   2077 flags |= reactor_event_write;
HITCBC 437   398974 if (FD_ISSET(fd, &except_fds)) 440   504592 if (FD_ISSET(fd, &except_fds))
HITGBC 438   ✗ flags |= reactor_event_error; 441   16 flags |= reactor_event_error;
439   442  
HITCBC 440   398974 if (flags == 0) 443   504592 if (flags == 0)
HITCBC 441   101084 continue; 444   157269 continue;
442   445  
HITCBC 443   297890 desc->add_ready_events(flags); 446   347323 desc->add_ready_events(flags);
444   447  
HITCBC 445   297890 bool expected = false; 448   347323 bool expected = false;
HITCBC 446   297890 if (desc->is_enqueued_.compare_exchange_strong( 449   347323 if (desc->is_enqueued_.compare_exchange_strong(
447   expected, true, std::memory_order_release, 450   expected, true, std::memory_order_release,
448   std::memory_order_relaxed)) 451   std::memory_order_relaxed))
449   { 452   {
HITCBC 450   297890 local_ops.push(desc); 453   347323 local_ops.push(desc);
451   } 454   }
452   } 455   }
453   } 456   }
454   457  
HITCBC 455   313378 lock.lock(); 458   363118 lock.lock();
456   459  
HITCBC 457   313378 completed_ops_.splice(local_ops); 460   363118 completed_ops_.splice(local_ops);
HITCBC 458   313378 } 461   363119 }
459   462  
460   } // namespace boost::corosio::detail 463   } // namespace boost::corosio::detail
461   464  
462   #endif // BOOST_COROSIO_HAS_SELECT 465   #endif // BOOST_COROSIO_HAS_SELECT
463   466  
464   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 467   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP