. /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 <unordered_map> 44   #include <unordered_map>
45   45  
46   namespace boost::corosio::detail { 46   namespace boost::corosio::detail {
47   47  
48   struct select_op; 48   struct select_op;
49   49  
50   /** POSIX scheduler using select() for I/O multiplexing. 50   /** POSIX scheduler using select() for I/O multiplexing.
51   51  
52   This scheduler implements the scheduler interface using the POSIX select() 52   This scheduler implements the scheduler interface using the POSIX select()
53   call for I/O event notification. It inherits the shared reactor threading 53   call for I/O event notification. It inherits the shared reactor threading
54   model from reactor_scheduler: signal state machine, inline completion 54   model from reactor_scheduler: signal state machine, inline completion
55   budget, work counting, and the do_one event loop. 55   budget, work counting, and the do_one event loop.
56   56  
57   The design mirrors epoll_scheduler for behavioral consistency: 57   The design mirrors epoll_scheduler for behavioral consistency:
58   - Same single-reactor thread coordination model 58   - Same single-reactor thread coordination model
59   - Same deferred I/O pattern (reactor marks ready; workers do I/O) 59   - Same deferred I/O pattern (reactor marks ready; workers do I/O)
60   - Same timer integration pattern 60   - Same timer integration pattern
61   61  
62   Known Limitations: 62   Known Limitations:
63   - FD_SETSIZE (~1024) limits maximum concurrent connections 63   - FD_SETSIZE (~1024) limits maximum concurrent connections
64   - O(n) scanning: rebuilds fd_sets each iteration 64   - O(n) scanning: rebuilds fd_sets each iteration
65   - Level-triggered only (no edge-triggered mode) 65   - Level-triggered only (no edge-triggered mode)
66   66  
67   @par Thread Safety 67   @par Thread Safety
68   All public member functions are thread-safe. 68   All public member functions are thread-safe.
69   */ 69   */
70   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler 70   class BOOST_COROSIO_DECL select_scheduler final : public reactor_scheduler
71   { 71   {
72   public: 72   public:
73   /** Construct the scheduler. 73   /** Construct the scheduler.
74   74  
75   Creates a self-pipe for reactor interruption. 75   Creates a self-pipe for reactor interruption.
76   76  
77   @param ctx Reference to the owning execution_context. 77   @param ctx Reference to the owning execution_context.
78   @param concurrency_hint Hint for expected thread count (unused). 78   @param concurrency_hint Hint for expected thread count (unused).
79   */ 79   */
80   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1); 80   select_scheduler(capy::execution_context& ctx, int concurrency_hint = -1);
81   81  
82   /// Destroy the scheduler. 82   /// Destroy the scheduler.
83   ~select_scheduler() override; 83   ~select_scheduler() override;
84   84  
85   select_scheduler(select_scheduler const&) = delete; 85   select_scheduler(select_scheduler const&) = delete;
86   select_scheduler& operator=(select_scheduler const&) = delete; 86   select_scheduler& operator=(select_scheduler const&) = delete;
87   87  
88   /// Shut down the scheduler, draining pending operations. 88   /// Shut down the scheduler, draining pending operations.
89   void shutdown() override; 89   void shutdown() override;
90   90  
91   /** Return the maximum file descriptor value supported. 91   /** Return the maximum file descriptor value supported.
92   92  
93   Returns FD_SETSIZE - 1, the maximum fd value that can be 93   Returns FD_SETSIZE - 1, the maximum fd value that can be
94   monitored by select(). Operations with fd >= FD_SETSIZE 94   monitored by select(). Operations with fd >= FD_SETSIZE
95   will fail with EINVAL. 95   will fail with EINVAL.
96   96  
97   @return The maximum supported file descriptor value. 97   @return The maximum supported file descriptor value.
98   */ 98   */
99   static constexpr int max_fd() noexcept 99   static constexpr int max_fd() noexcept
100   { 100   {
101   return FD_SETSIZE - 1; 101   return FD_SETSIZE - 1;
102   } 102   }
103   103  
104   /** Register a descriptor for persistent monitoring. 104   /** Register a descriptor for persistent monitoring.
105   105  
106   The fd is added to the registered_descs_ map and will be 106   The fd is added to the registered_descs_ map and will be
107   included in subsequent select() calls. The reactor is 107   included in subsequent select() calls. The reactor is
108   interrupted so a blocked select() rebuilds its fd_sets. 108   interrupted so a blocked select() rebuilds its fd_sets.
109   109  
110   @param fd The file descriptor to register. 110   @param fd The file descriptor to register.
111   @param desc Pointer to descriptor state for this fd. 111   @param desc Pointer to descriptor state for this fd.
112   */ 112   */
113   void register_descriptor(int fd, reactor_descriptor_state* desc) const; 113   void register_descriptor(int fd, reactor_descriptor_state* desc) const;
114   114  
115   /** Deregister a persistently registered descriptor. 115   /** Deregister a persistently registered descriptor.
116   116  
117   @param fd The file descriptor to deregister. 117   @param fd The file descriptor to deregister.
118   */ 118   */
119   void deregister_descriptor(int fd) const; 119   void deregister_descriptor(int fd) const;
120   120  
121   /** Interrupt the reactor so it rebuilds its fd_sets. 121   /** Interrupt the reactor so it rebuilds its fd_sets.
122   122  
123   Called when a write or connect op is registered after 123   Called when a write or connect op is registered after
124   the reactor's snapshot was taken. Without this, select() 124   the reactor's snapshot was taken. Without this, select()
125   may block not watching for writability on the fd. 125   may block not watching for writability on the fd.
126   */ 126   */
127   void notify_reactor() const; 127   void notify_reactor() const;
128   128  
129   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp). 129   /// Watch the read end of the POSIX signal self-pipe (see scheduler.hpp).
HITCBC 130   41 void register_signal_reader(int read_fd) override 130   41 void register_signal_reader(int read_fd) override
131   { 131   {
HITCBC 132   41 register_descriptor(read_fd, signal_pipe_reader_.arm()); 132   41 register_descriptor(read_fd, signal_pipe_reader_.arm());
HITCBC 133   41 } 133   41 }
134   134  
135   private: 135   private:
136   void 136   void
137   run_task(lock_type& lock, context_type* ctx, 137   run_task(lock_type& lock, context_type* ctx,
138   long timeout_us) override; 138   long timeout_us) override;
139   void interrupt_reactor() const override; 139   void interrupt_reactor() const override;
140   long calculate_timeout(long requested_timeout_us) const; 140   long calculate_timeout(long requested_timeout_us) const;
141   141  
142   // Watches the global signal self-pipe's read end (armed lazily by 142   // Watches the global signal self-pipe's read end (armed lazily by
143   // register_signal_reader on the first signal registration). 143   // register_signal_reader on the first signal registration).
144   reactor_signal_pipe_reader signal_pipe_reader_; 144   reactor_signal_pipe_reader signal_pipe_reader_;
145   145  
146   // Self-pipe for interrupting select() 146   // Self-pipe for interrupting select()
147   int pipe_fds_[2]; // [0]=read, [1]=write 147   int pipe_fds_[2]; // [0]=read, [1]=write
148   148  
149   // Per-fd tracking for fd_set building 149   // Per-fd tracking for fd_set building
150   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_; 150   mutable std::unordered_map<int, reactor_descriptor_state*> registered_descs_;
151   mutable int max_fd_ = -1; 151   mutable int max_fd_ = -1;
152   }; 152   };
153   153  
HITCBC 154   585 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int) 154   585 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 155   585 : pipe_fds_{-1, -1} 155   585 : pipe_fds_{-1, -1}
HITCBC 156   585 , max_fd_(-1) 156   585 , max_fd_(-1)
157   { 157   {
HITCBC 158   585 if (::pipe(pipe_fds_) < 0) 158   585 if (::pipe(pipe_fds_) < 0)
MISUBC 159   ✗ detail::throw_system_error(make_err(errno), "pipe"); 159   ✗ detail::throw_system_error(make_err(errno), "pipe");
160   160  
HITCBC 161   1755 for (int i = 0; i < 2; ++i) 161   1755 for (int i = 0; i < 2; ++i)
162   { 162   {
HITCBC 163   1170 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 163   1170 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 164   1170 if (flags == -1) 164   1170 if (flags == -1)
165   { 165   {
MISUBC 166   ✗ int errn = errno; 166   ✗ int errn = errno;
MISUBC 167   ✗ ::close(pipe_fds_[0]); 167   ✗ ::close(pipe_fds_[0]);
MISUBC 168   ✗ ::close(pipe_fds_[1]); 168   ✗ ::close(pipe_fds_[1]);
MISUBC 169   ✗ detail::throw_system_error(make_err(errn), "fcntl F_GETFL"); 169   ✗ detail::throw_system_error(make_err(errn), "fcntl F_GETFL");
170   } 170   }
HITCBC 171   1170 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1) 171   1170 if (::fcntl(pipe_fds_[i], F_SETFL, flags | O_NONBLOCK) == -1)
172   { 172   {
MISUBC 173   ✗ int errn = errno; 173   ✗ int errn = errno;
MISUBC 174   ✗ ::close(pipe_fds_[0]); 174   ✗ ::close(pipe_fds_[0]);
MISUBC 175   ✗ ::close(pipe_fds_[1]); 175   ✗ ::close(pipe_fds_[1]);
MISUBC 176   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFL"); 176   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFL");
177   } 177   }
HITCBC 178   1170 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1) 178   1170 if (::fcntl(pipe_fds_[i], F_SETFD, FD_CLOEXEC) == -1)
179   { 179   {
MISUBC 180   ✗ int errn = errno; 180   ✗ int errn = errno;
MISUBC 181   ✗ ::close(pipe_fds_[0]); 181   ✗ ::close(pipe_fds_[0]);
MISUBC 182   ✗ ::close(pipe_fds_[1]); 182   ✗ ::close(pipe_fds_[1]);
MISUBC 183   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFD"); 183   ✗ detail::throw_system_error(make_err(errn), "fcntl F_SETFD");
184   } 184   }
185   } 185   }
186   186  
HITCBC 187   585 timer_svc_ = &get_timer_service(ctx, *this); 187   585 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 188   585 timer_svc_->set_on_earliest_changed( 188   585 timer_svc_->set_on_earliest_changed(
HITCBC 189   3533 timer_service::callback(this, [](void* p) { 189   3320 timer_service::callback(this, [](void* p) {
HITCBC 190   2948 static_cast<select_scheduler*>(p)->interrupt_reactor(); 190   2735 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 191   2948 })); 191   2735 }));
192   192  
HITCBC 193   585 get_resolver_service(ctx, *this); 193   585 get_resolver_service(ctx, *this);
HITCBC 194   585 get_signal_service(ctx, *this); 194   585 get_signal_service(ctx, *this);
HITCBC 195   585 get_stream_file_service(ctx, *this); 195   585 get_stream_file_service(ctx, *this);
HITCBC 196   585 get_random_access_file_service(ctx, *this); 196   585 get_random_access_file_service(ctx, *this);
197   197  
HITCBC 198   585 completed_ops_.push(&task_op_); 198   585 completed_ops_.push(&task_op_);
HITCBC 199   585 } 199   585 }
200   200  
HITCBC 201   1170 inline select_scheduler::~select_scheduler() 201   1170 inline select_scheduler::~select_scheduler()
202   { 202   {
HITCBC 203   585 if (pipe_fds_[0] >= 0) 203   585 if (pipe_fds_[0] >= 0)
HITCBC 204   585 ::close(pipe_fds_[0]); 204   585 ::close(pipe_fds_[0]);
HITCBC 205   585 if (pipe_fds_[1] >= 0) 205   585 if (pipe_fds_[1] >= 0)
HITCBC 206   585 ::close(pipe_fds_[1]); 206   585 ::close(pipe_fds_[1]);
HITCBC 207   1170 } 207   1170 }
208   208  
209   inline void 209   inline void
HITCBC 210   585 select_scheduler::shutdown() 210   585 select_scheduler::shutdown()
211   { 211   {
HITCBC 212   585 shutdown_drain(); 212   585 shutdown_drain();
213   213  
HITCBC 214   585 if (pipe_fds_[1] >= 0) 214   585 if (pipe_fds_[1] >= 0)
HITCBC 215   585 interrupt_reactor(); 215   585 interrupt_reactor();
HITCBC 216   585 } 216   585 }
217   217  
218   inline void 218   inline void
HITCBC 219   4680 select_scheduler::register_descriptor( 219   4274 select_scheduler::register_descriptor(
220   int fd, reactor_descriptor_state* desc) const 220   int fd, reactor_descriptor_state* desc) const
221   { 221   {
HITCBC 222   4680 if (fd < 0 || fd >= FD_SETSIZE) 222   4274 if (fd < 0 || fd >= FD_SETSIZE)
MISUBC 223   ✗ detail::throw_system_error(make_err(EINVAL), "select: fd out of range"); 223   ✗ detail::throw_system_error(make_err(EINVAL), "select: fd out of range");
224   224  
HITCBC 225   4680 desc->registered_events = reactor_event_read | reactor_event_write; 225   4274 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 226   4680 desc->fd = fd; 226   4274 desc->fd = fd;
HITCBC 227   4680 desc->scheduler_ = this; 227   4274 desc->scheduler_ = this;
HITCBC 228   4680 desc->mutex.set_enabled(reactor_io_locking_); 228   4274 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 229   4680 desc->ready_events_.store(0, std::memory_order_relaxed); 229   4274 desc->ready_events_.store(0, std::memory_order_relaxed);
230   230  
231   { 231   {
HITCBC 232   4680 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 232   4274 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 233   4680 desc->impl_ref_.reset(); 233   4274 desc->impl_ref_.reset();
HITCBC 234   4680 desc->read_ready = false; 234   4274 desc->read_ready = false;
HITCBC 235   4680 desc->write_ready = false; 235   4274 desc->write_ready = false;
HITCBC 236   4680 } 236   4274 }
237   237  
238   { 238   {
HITCBC 239   4680 mutex_type::scoped_lock lock(mutex_); 239   4274 mutex_type::scoped_lock lock(mutex_);
HITCBC 240   4680 registered_descs_[fd] = desc; 240   4274 registered_descs_[fd] = desc;
HITCBC 241   4680 if (fd > max_fd_) 241   4274 if (fd > max_fd_)
HITCBC 242   4675 max_fd_ = fd; 242   4269 max_fd_ = fd;
HITCBC 243   4680 } 243   4274 }
244   244  
HITCBC 245   4680 interrupt_reactor(); 245   4274 interrupt_reactor();
HITCBC 246   4680 } 246   4274 }
247   247  
248   inline void 248   inline void
HITCBC 249   4639 select_scheduler::deregister_descriptor(int fd) const 249   4233 select_scheduler::deregister_descriptor(int fd) const
250   { 250   {
HITCBC 251   4639 mutex_type::scoped_lock lock(mutex_); 251   4233 mutex_type::scoped_lock lock(mutex_);
252   252  
HITCBC 253   4639 auto it = registered_descs_.find(fd); 253   4233 auto it = registered_descs_.find(fd);
HITCBC 254   4639 if (it == registered_descs_.end()) 254   4233 if (it == registered_descs_.end())
MISUBC 255   ✗ return; 255   ✗ return;
256   256  
HITCBC 257   4639 registered_descs_.erase(it); 257   4233 registered_descs_.erase(it);
258   258  
HITCBC 259   4639 if (fd == max_fd_) 259   4233 if (fd == max_fd_)
260   { 260   {
HITCBC 261   4519 max_fd_ = pipe_fds_[0]; 261   4113 max_fd_ = pipe_fds_[0];
HITCBC 262   8785 for (auto& [registered_fd, state] : registered_descs_) 262   7973 for (auto& [registered_fd, state] : registered_descs_)
263   { 263   {
HITCBC 264   4266 if (registered_fd > max_fd_) 264   3860 if (registered_fd > max_fd_)
HITCBC 265   4219 max_fd_ = registered_fd; 265   3813 max_fd_ = registered_fd;
266   } 266   }
267   } 267   }
HITCBC 268   4639 } 268   4233 }
269   269  
270   inline void 270   inline void
HITCBC 271   2223 select_scheduler::notify_reactor() const 271   2020 select_scheduler::notify_reactor() const
272   { 272   {
HITCBC 273   2223 interrupt_reactor(); 273   2020 interrupt_reactor();
HITCBC 274   2223 } 274   2020 }
275   275  
276   inline void 276   inline void
HITCBC 277   10888 select_scheduler::interrupt_reactor() const 277   10067 select_scheduler::interrupt_reactor() const
278   { 278   {
HITCBC 279   10888 char byte = 1; 279   10067 char byte = 1;
HITCBC 280   10888 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 280   10067 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 281   10888 } 281   10067 }
282   282  
283   inline long 283   inline long
HITCBC 284   200296 select_scheduler::calculate_timeout(long requested_timeout_us) const 284   177688 select_scheduler::calculate_timeout(long requested_timeout_us) const
285   { 285   {
HITCBC 286   200296 if (requested_timeout_us == 0) 286   177688 if (requested_timeout_us == 0)
MISUBC 287   ✗ return 0; 287   ✗ return 0;
288   288  
HITCBC 289   200296 auto nearest = timer_svc_->nearest_expiry(); 289   177688 auto nearest = timer_svc_->nearest_expiry();
HITCBC 290   200296 if (nearest == timer_service::time_point::max()) 290   177688 if (nearest == timer_service::time_point::max())
HITCBC 291   568 return requested_timeout_us; 291   570 return requested_timeout_us;
292   292  
HITCBC 293   199728 auto now = std::chrono::steady_clock::now(); 293   177118 auto now = std::chrono::steady_clock::now();
HITCBC 294   199728 if (nearest <= now) 294   177118 if (nearest <= now)
HITCBC 295   630 return 0; 295   659 return 0;
296   296  
297   auto timer_timeout_us = 297   auto timer_timeout_us =
HITCBC 298   199098 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 298   176459 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 299   199098 .count(); 299   176459 .count();
300   300  
HITCBC 301   199098 constexpr auto long_max = 301   176459 constexpr auto long_max =
302   static_cast<long long>((std::numeric_limits<long>::max)()); 302   static_cast<long long>((std::numeric_limits<long>::max)());
303   auto capped_timer_us = 303   auto capped_timer_us =
HITCBC 304   199098 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 304   176459 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 305   199098 static_cast<long long>(0)), 305   176459 static_cast<long long>(0)),
HITCBC 306   199098 long_max); 306   176459 long_max);
307   307  
HITCBC 308   199098 if (requested_timeout_us < 0) 308   176459 if (requested_timeout_us < 0)
HITCBC 309   199098 return static_cast<long>(capped_timer_us); 309   176459 return static_cast<long>(capped_timer_us);
310   310  
311   return static_cast<long>( 311   return static_cast<long>(
MISUBC 312   ✗ (std::min)(static_cast<long long>(requested_timeout_us), 312   ✗ (std::min)(static_cast<long long>(requested_timeout_us),
MISUBC 313   ✗ capped_timer_us)); 313   ✗ capped_timer_us));
314   } 314   }
315   315  
316   inline void 316   inline void
HITCBC 317   225651 select_scheduler::run_task( 317   195318 select_scheduler::run_task(
318   lock_type& lock, context_type* ctx, long timeout_us) 318   lock_type& lock, context_type* ctx, long timeout_us)
319   { 319   {
320   long effective_timeout_us = 320   long effective_timeout_us =
HITCBC 321   225651 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 321   195318 task_interrupted_ ? 0 : calculate_timeout(timeout_us);
322   322  
323   // Snapshot registered descriptors while holding lock. 323   // Snapshot registered descriptors while holding lock.
324   // Record which fds need write monitoring to avoid a hot loop: 324   // Record which fds need write monitoring to avoid a hot loop:
325   // select is level-triggered so writable sockets (nearly always 325   // select is level-triggered so writable sockets (nearly always
326   // writable) would cause select() to return immediately every 326   // writable) would cause select() to return immediately every
327   // iteration if unconditionally added to write_fds. 327   // iteration if unconditionally added to write_fds.
328   struct fd_entry 328   struct fd_entry
329   { 329   {
330   int fd; 330   int fd;
331   reactor_descriptor_state* desc; 331   reactor_descriptor_state* desc;
332   bool needs_write; 332   bool needs_write;
333   }; 333   };
334   fd_entry snapshot[FD_SETSIZE]; 334   fd_entry snapshot[FD_SETSIZE];
HITCBC 335   225651 int snapshot_count = 0; 335   195318 int snapshot_count = 0;
336   336  
HITCBC 337   589304 for (auto& [fd, desc] : registered_descs_) 337   490418 for (auto& [fd, desc] : registered_descs_)
338   { 338   {
HITCBC 339   363653 if (snapshot_count < FD_SETSIZE) 339   295100 if (snapshot_count < FD_SETSIZE)
340   { 340   {
HITCBC 341   363653 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 341   295100 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 342   363653 snapshot[snapshot_count].fd = fd; 342   295100 snapshot[snapshot_count].fd = fd;
HITCBC 343   363653 snapshot[snapshot_count].desc = desc; 343   295100 snapshot[snapshot_count].desc = desc;
HITCBC 344   363653 snapshot[snapshot_count].needs_write = 344   295100 snapshot[snapshot_count].needs_write =
HITCBC 345   363653 (desc->write_op || desc->connect_op); 345   295100 (desc->write_op || desc->connect_op);
HITCBC 346   363653 ++snapshot_count; 346   295100 ++snapshot_count;
HITCBC 347   363653 } 347   295100 }
348   } 348   }
349   349  
HITCBC 350   225651 if (lock.owns_lock()) 350   195318 if (lock.owns_lock())
HITCBC 351   200297 lock.unlock(); 351   177689 lock.unlock();
352   352  
HITCBC 353   225651 task_cleanup on_exit{this, &lock, ctx}; 353   195318 task_cleanup on_exit{this, &lock, ctx};
354   354  
355   fd_set read_fds, write_fds, except_fds; 355   fd_set read_fds, write_fds, except_fds;
HITCBC 356   3836067 FD_ZERO(&read_fds); 356   3320406 FD_ZERO(&read_fds);
HITCBC 357   3836067 FD_ZERO(&write_fds); 357   3320406 FD_ZERO(&write_fds);
HITCBC 358   3836067 FD_ZERO(&except_fds); 358   3320406 FD_ZERO(&except_fds);
359   359  
HITCBC 360   225651 FD_SET(pipe_fds_[0], &read_fds); 360   195318 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 361   225651 int nfds = pipe_fds_[0]; 361   195318 int nfds = pipe_fds_[0];
362   362  
HITCBC 363   589304 for (int i = 0; i < snapshot_count; ++i) 363   490418 for (int i = 0; i < snapshot_count; ++i)
364   { 364   {
HITCBC 365   363653 int fd = snapshot[i].fd; 365   295100 int fd = snapshot[i].fd;
HITCBC 366   363653 FD_SET(fd, &read_fds); 366   295100 FD_SET(fd, &read_fds);
HITCBC 367   363653 if (snapshot[i].needs_write) 367   295100 if (snapshot[i].needs_write)
HITCBC 368   13067 FD_SET(fd, &write_fds); 368   5123 FD_SET(fd, &write_fds);
HITCBC 369   363653 FD_SET(fd, &except_fds); 369   295100 FD_SET(fd, &except_fds);
HITCBC 370   363653 if (fd > nfds) 370   295100 if (fd > nfds)
HITCBC 371   225334 nfds = fd; 371   195006 nfds = fd;
372   } 372   }
373   373  
374   struct timeval tv; 374   struct timeval tv;
HITCBC 375   225651 struct timeval* tv_ptr = nullptr; 375   195318 struct timeval* tv_ptr = nullptr;
HITCBC 376   225651 if (effective_timeout_us >= 0) 376   195318 if (effective_timeout_us >= 0)
377   { 377   {
HITCBC 378   225087 tv.tv_sec = effective_timeout_us / 1000000; 378   194752 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 379   225087 tv.tv_usec = effective_timeout_us % 1000000; 379   194752 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 380   225087 tv_ptr = &tv; 380   194752 tv_ptr = &tv;
381   } 381   }
382   382  
HITCBC 383   225651 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 383   195318 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr);
384   384  
385   // EINTR: signal interrupted select(), just retry. 385   // EINTR: signal interrupted select(), just retry.
386   // EBADF: an fd was closed between snapshot and select(); retry 386   // EBADF: an fd was closed between snapshot and select(); retry
387   // with a fresh snapshot from registered_descs_. 387   // with a fresh snapshot from registered_descs_.
HITCBC 388   225651 if (ready < 0) 388   195318 if (ready < 0)
389   { 389   {
MISUBC 390   ✗ if (errno == EINTR || errno == EBADF) 390   ✗ if (errno == EINTR || errno == EBADF)
MISUBC 391   ✗ return; 391   ✗ return;
MISUBC 392   ✗ detail::throw_system_error(make_err(errno), "select"); 392   ✗ detail::throw_system_error(make_err(errno), "select");
393   } 393   }
394   394  
395   // Process timers outside the lock 395   // Process timers outside the lock
HITCBC 396   225651 timer_svc_->process_expired(); 396   195318 timer_svc_->process_expired();
397   397  
HITCBC 398   225651 ready_queue local_ops; 398   195318 ready_queue local_ops;
399   399  
HITCBC 400   225651 if (ready > 0) 400   195318 if (ready > 0)
401   { 401   {
HITCBC 402   208492 if (FD_ISSET(pipe_fds_[0], &read_fds)) 402   182963 if (FD_ISSET(pipe_fds_[0], &read_fds))
403   { 403   {
404   char buf[256]; 404   char buf[256];
HITCBC 405   9832 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 405   9012 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
406   { 406   {
407   } 407   }
408   } 408   }
409   409  
HITCBC 410   523522 for (int i = 0; i < snapshot_count; ++i) 410   444362 for (int i = 0; i < snapshot_count; ++i)
411   { 411   {
HITCBC 412   315030 int fd = snapshot[i].fd; 412   261399 int fd = snapshot[i].fd;
HITCBC 413   315030 reactor_descriptor_state* desc = snapshot[i].desc; 413   261399 reactor_descriptor_state* desc = snapshot[i].desc;
414   414  
HITCBC 415   315030 std::uint32_t flags = 0; 415   261399 std::uint32_t flags = 0;
HITCBC 416   315030 if (FD_ISSET(fd, &read_fds)) 416   261399 if (FD_ISSET(fd, &read_fds))
HITCBC 417   205947 flags |= reactor_event_read; 417   180622 flags |= reactor_event_read;
HITCBC 418   315030 if (FD_ISSET(fd, &write_fds)) 418   261399 if (FD_ISSET(fd, &write_fds))
HITCBC 419   2220 flags |= reactor_event_write; 419   2017 flags |= reactor_event_write;
HITCBC 420   315030 if (FD_ISSET(fd, &except_fds)) 420   261399 if (FD_ISSET(fd, &except_fds))
MISUBC 421   ✗ flags |= reactor_event_error; 421   ✗ flags |= reactor_event_error;
422   422  
HITCBC 423   315030 if (flags == 0) 423   261399 if (flags == 0)
HITCBC 424   106874 continue; 424   78770 continue;
425   425  
HITCBC 426   208156 desc->add_ready_events(flags); 426   182629 desc->add_ready_events(flags);
427   427  
HITCBC 428   208156 bool expected = false; 428   182629 bool expected = false;
HITCBC 429   208156 if (desc->is_enqueued_.compare_exchange_strong( 429   182629 if (desc->is_enqueued_.compare_exchange_strong(
430   expected, true, std::memory_order_release, 430   expected, true, std::memory_order_release,
431   std::memory_order_relaxed)) 431   std::memory_order_relaxed))
432   { 432   {
HITCBC 433   208156 local_ops.push(desc); 433   182629 local_ops.push(desc);
434   } 434   }
435   } 435   }
436   } 436   }
437   437  
HITCBC 438   225651 lock.lock(); 438   195318 lock.lock();
439   439  
HITCBC 440   225651 completed_ops_.splice(local_ops); 440   195318 completed_ops_.splice(local_ops);
HITCBC 441   225651 } 441   195318 }
442   442  
443   } // namespace boost::corosio::detail 443   } // namespace boost::corosio::detail
444   444  
445   #endif // BOOST_COROSIO_HAS_SELECT 445   #endif // BOOST_COROSIO_HAS_SELECT
446   446  
447   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP 447   #endif // BOOST_COROSIO_NATIVE_DETAIL_SELECT_SELECT_SCHEDULER_HPP