. /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   591 inline select_scheduler::select_scheduler(capy::execution_context& ctx, int)
HITCBC 155   585 : pipe_fds_{-1, -1} 155   591 : pipe_fds_{-1, -1}
HITCBC 156   585 , max_fd_(-1) 156   591 , max_fd_(-1)
157   { 157   {
HITCBC 158   585 if (::pipe(pipe_fds_) < 0) 158   591 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   1773 for (int i = 0; i < 2; ++i)
162   { 162   {
HITCBC 163   1170 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0); 163   1182 int flags = ::fcntl(pipe_fds_[i], F_GETFL, 0);
HITCBC 164   1170 if (flags == -1) 164   1182 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   1182 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   1182 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   591 timer_svc_ = &get_timer_service(ctx, *this);
HITCBC 188   585 timer_svc_->set_on_earliest_changed( 188   591 timer_svc_->set_on_earliest_changed(
HITCBC 189   3284 timer_service::callback(this, [](void* p) { 189   3381 timer_service::callback(this, [](void* p) {
HITCBC 190   2699 static_cast<select_scheduler*>(p)->interrupt_reactor(); 190   2790 static_cast<select_scheduler*>(p)->interrupt_reactor();
HITCBC 191   2699 })); 191   2790 }));
192   192  
HITCBC 193   585 get_resolver_service(ctx, *this); 193   591 get_resolver_service(ctx, *this);
HITCBC 194   585 get_signal_service(ctx, *this); 194   591 get_signal_service(ctx, *this);
HITCBC 195   585 get_stream_file_service(ctx, *this); 195   591 get_stream_file_service(ctx, *this);
HITCBC 196   585 get_random_access_file_service(ctx, *this); 196   591 get_random_access_file_service(ctx, *this);
197   197  
HITCBC 198   585 completed_ops_.push(&task_op_); 198   591 completed_ops_.push(&task_op_);
HITCBC 199   585 } 199   591 }
200   200  
HITCBC 201   1170 inline select_scheduler::~select_scheduler() 201   1182 inline select_scheduler::~select_scheduler()
202   { 202   {
HITCBC 203   585 if (pipe_fds_[0] >= 0) 203   591 if (pipe_fds_[0] >= 0)
HITCBC 204   585 ::close(pipe_fds_[0]); 204   591 ::close(pipe_fds_[0]);
HITCBC 205   585 if (pipe_fds_[1] >= 0) 205   591 if (pipe_fds_[1] >= 0)
HITCBC 206   585 ::close(pipe_fds_[1]); 206   591 ::close(pipe_fds_[1]);
HITCBC 207   1170 } 207   1182 }
208   208  
209   inline void 209   inline void
HITCBC 210   585 select_scheduler::shutdown() 210   591 select_scheduler::shutdown()
211   { 211   {
HITCBC 212   585 shutdown_drain(); 212   591 shutdown_drain();
213   213  
HITCBC 214   585 if (pipe_fds_[1] >= 0) 214   591 if (pipe_fds_[1] >= 0)
HITCBC 215   585 interrupt_reactor(); 215   591 interrupt_reactor();
HITCBC 216   585 } 216   591 }
217   217  
218   inline void 218   inline void
HITCBC 219   4324 select_scheduler::register_descriptor( 219   4381 select_scheduler::register_descriptor(
220   int fd, reactor_descriptor_state* desc) const 220   int fd, reactor_descriptor_state* desc) const
221   { 221   {
HITCBC 222   4324 if (fd < 0 || fd >= FD_SETSIZE) 222   4381 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   4324 desc->registered_events = reactor_event_read | reactor_event_write; 225   4381 desc->registered_events = reactor_event_read | reactor_event_write;
HITCBC 226   4324 desc->fd = fd; 226   4381 desc->fd = fd;
HITCBC 227   4324 desc->scheduler_ = this; 227   4381 desc->scheduler_ = this;
HITCBC 228   4324 desc->mutex.set_enabled(reactor_io_locking_); 228   4381 desc->mutex.set_enabled(reactor_io_locking_);
HITCBC 229   4324 desc->ready_events_.store(0, std::memory_order_relaxed); 229   4381 desc->ready_events_.store(0, std::memory_order_relaxed);
230   230  
231   { 231   {
HITCBC 232   4324 conditionally_enabled_mutex::scoped_lock lock(desc->mutex); 232   4381 conditionally_enabled_mutex::scoped_lock lock(desc->mutex);
HITCBC 233   4324 desc->impl_ref_.reset(); 233   4381 desc->impl_ref_.reset();
HITCBC 234   4324 desc->read_ready = false; 234   4381 desc->read_ready = false;
HITCBC 235   4324 desc->write_ready = false; 235   4381 desc->write_ready = false;
HITCBC 236   4324 } 236   4381 }
237   237  
238   { 238   {
HITCBC 239   4324 mutex_type::scoped_lock lock(mutex_); 239   4381 mutex_type::scoped_lock lock(mutex_);
HITCBC 240   4324 registered_descs_[fd] = desc; 240   4381 registered_descs_[fd] = desc;
HITCBC 241   4324 if (fd > max_fd_) 241   4381 if (fd > max_fd_)
HITCBC 242   4319 max_fd_ = fd; 242   4376 max_fd_ = fd;
HITCBC 243   4324 } 243   4381 }
244   244  
HITCBC 245   4324 interrupt_reactor(); 245   4381 interrupt_reactor();
HITCBC 246   4324 } 246   4381 }
247   247  
248   inline void 248   inline void
HITCBC 249   4283 select_scheduler::deregister_descriptor(int fd) const 249   4340 select_scheduler::deregister_descriptor(int fd) const
250   { 250   {
HITCBC 251   4283 mutex_type::scoped_lock lock(mutex_); 251   4340 mutex_type::scoped_lock lock(mutex_);
252   252  
HITCBC 253   4283 auto it = registered_descs_.find(fd); 253   4340 auto it = registered_descs_.find(fd);
HITCBC 254   4283 if (it == registered_descs_.end()) 254   4340 if (it == registered_descs_.end())
MISUBC 255   ✗ return; 255   ✗ return;
256   256  
HITCBC 257   4283 registered_descs_.erase(it); 257   4340 registered_descs_.erase(it);
258   258  
HITCBC 259   4283 if (fd == max_fd_) 259   4340 if (fd == max_fd_)
260   { 260   {
HITCBC 261   4163 max_fd_ = pipe_fds_[0]; 261   4218 max_fd_ = pipe_fds_[0];
HITCBC 262   8073 for (auto& [registered_fd, state] : registered_descs_) 262   8182 for (auto& [registered_fd, state] : registered_descs_)
263   { 263   {
HITCBC 264   3910 if (registered_fd > max_fd_) 264   3964 if (registered_fd > max_fd_)
HITCBC 265   3863 max_fd_ = registered_fd; 265   3917 max_fd_ = registered_fd;
266   } 266   }
267   } 267   }
HITCBC 268   4283 } 268   4340 }
269   269  
270   inline void 270   inline void
HITCBC 271   2045 select_scheduler::notify_reactor() const 271   2073 select_scheduler::notify_reactor() const
272   { 272   {
HITCBC 273   2045 interrupt_reactor(); 273   2073 interrupt_reactor();
HITCBC 274   2045 } 274   2073 }
275   275  
276   inline void 276   inline void
HITCBC 277   10106 select_scheduler::interrupt_reactor() const 277   10294 select_scheduler::interrupt_reactor() const
278   { 278   {
HITCBC 279   10106 char byte = 1; 279   10294 char byte = 1;
HITCBC 280   10106 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1); 280   10294 [[maybe_unused]] auto r = ::write(pipe_fds_[1], &byte, 1);
HITCBC 281   10106 } 281   10294 }
282   282  
283   inline long 283   inline long
HITCBC 284   199346 select_scheduler::calculate_timeout(long requested_timeout_us) const 284   215080 select_scheduler::calculate_timeout(long requested_timeout_us) const
285   { 285   {
HITCBC 286   199346 if (requested_timeout_us == 0) 286   215080 if (requested_timeout_us == 0)
MISUBC 287   ✗ return 0; 287   ✗ return 0;
288   288  
HITCBC 289   199346 auto nearest = timer_svc_->nearest_expiry(); 289   215080 auto nearest = timer_svc_->nearest_expiry();
HITCBC 290   199346 if (nearest == timer_service::time_point::max()) 290   215080 if (nearest == timer_service::time_point::max())
HITCBC 291   567 return requested_timeout_us; 291   568 return requested_timeout_us;
292   292  
HITCBC 293   198779 auto now = std::chrono::steady_clock::now(); 293   214512 auto now = std::chrono::steady_clock::now();
HITCBC 294   198779 if (nearest <= now) 294   214512 if (nearest <= now)
HITCBC 295   598 return 0; 295   683 return 0;
296   296  
297   auto timer_timeout_us = 297   auto timer_timeout_us =
HITCBC 298   198181 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now) 298   213829 std::chrono::duration_cast<std::chrono::microseconds>(nearest - now)
HITCBC 299   198181 .count(); 299   213829 .count();
300   300  
HITCBC 301   198181 constexpr auto long_max = 301   213829 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   198181 (std::min)((std::max)(static_cast<long long>(timer_timeout_us), 304   213829 (std::min)((std::max)(static_cast<long long>(timer_timeout_us),
HITCBC 305   198181 static_cast<long long>(0)), 305   213829 static_cast<long long>(0)),
HITCBC 306   198181 long_max); 306   213829 long_max);
307   307  
HITCBC 308   198181 if (requested_timeout_us < 0) 308   213829 if (requested_timeout_us < 0)
HITCBC 309   198181 return static_cast<long>(capped_timer_us); 309   213829 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   219780 select_scheduler::run_task( 317   235775 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   219780 task_interrupted_ ? 0 : calculate_timeout(timeout_us); 321   235775 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   219780 int snapshot_count = 0; 335   235775 int snapshot_count = 0;
336   336  
HITCBC 337   569110 for (auto& [fd, desc] : registered_descs_) 337   616455 for (auto& [fd, desc] : registered_descs_)
338   { 338   {
HITCBC 339   349330 if (snapshot_count < FD_SETSIZE) 339   380680 if (snapshot_count < FD_SETSIZE)
340   { 340   {
HITCBC 341   349330 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex); 341   380680 conditionally_enabled_mutex::scoped_lock desc_lock(desc->mutex);
HITCBC 342   349330 snapshot[snapshot_count].fd = fd; 342   380680 snapshot[snapshot_count].fd = fd;
HITCBC 343   349330 snapshot[snapshot_count].desc = desc; 343   380680 snapshot[snapshot_count].desc = desc;
HITCBC 344   349330 snapshot[snapshot_count].needs_write = 344   380680 snapshot[snapshot_count].needs_write =
HITCBC 345   349330 (desc->write_op || desc->connect_op); 345   380680 (desc->write_op || desc->connect_op);
HITCBC 346   349330 ++snapshot_count; 346   380680 ++snapshot_count;
HITCBC 347   349330 } 347   380680 }
348   } 348   }
349   349  
HITCBC 350   219780 if (lock.owns_lock()) 350   235775 if (lock.owns_lock())
HITCBC 351   199347 lock.unlock(); 351   215081 lock.unlock();
352   352  
HITCBC 353   219780 task_cleanup on_exit{this, &lock, ctx}; 353   235775 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   3736260 FD_ZERO(&read_fds); 356   4008175 FD_ZERO(&read_fds);
HITCBC 357   3736260 FD_ZERO(&write_fds); 357   4008175 FD_ZERO(&write_fds);
HITCBC 358   3736260 FD_ZERO(&except_fds); 358   4008175 FD_ZERO(&except_fds);
359   359  
HITCBC 360   219780 FD_SET(pipe_fds_[0], &read_fds); 360   235775 FD_SET(pipe_fds_[0], &read_fds);
HITCBC 361   219780 int nfds = pipe_fds_[0]; 361   235775 int nfds = pipe_fds_[0];
362   362  
HITCBC 363   569110 for (int i = 0; i < snapshot_count; ++i) 363   616455 for (int i = 0; i < snapshot_count; ++i)
364   { 364   {
HITCBC 365   349330 int fd = snapshot[i].fd; 365   380680 int fd = snapshot[i].fd;
HITCBC 366   349330 FD_SET(fd, &read_fds); 366   380680 FD_SET(fd, &read_fds);
HITCBC 367   349330 if (snapshot[i].needs_write) 367   380680 if (snapshot[i].needs_write)
HITCBC 368   12947 FD_SET(fd, &write_fds); 368   12923 FD_SET(fd, &write_fds);
HITCBC 369   349330 FD_SET(fd, &except_fds); 369   380680 FD_SET(fd, &except_fds);
HITCBC 370   349330 if (fd > nfds) 370   380680 if (fd > nfds)
HITCBC 371   219469 nfds = fd; 371   235452 nfds = fd;
372   } 372   }
373   373  
374   struct timeval tv; 374   struct timeval tv;
HITCBC 375   219780 struct timeval* tv_ptr = nullptr; 375   235775 struct timeval* tv_ptr = nullptr;
HITCBC 376   219780 if (effective_timeout_us >= 0) 376   235775 if (effective_timeout_us >= 0)
377   { 377   {
HITCBC 378   219217 tv.tv_sec = effective_timeout_us / 1000000; 378   235211 tv.tv_sec = effective_timeout_us / 1000000;
HITCBC 379   219217 tv.tv_usec = effective_timeout_us % 1000000; 379   235211 tv.tv_usec = effective_timeout_us % 1000000;
HITCBC 380   219217 tv_ptr = &tv; 380   235211 tv_ptr = &tv;
381   } 381   }
382   382  
HITCBC 383   219780 int ready = ::select(nfds + 1, &read_fds, &write_fds, &except_fds, tv_ptr); 383   235775 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   219780 if (ready < 0) 388   235775 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   219780 timer_svc_->process_expired(); 396   235775 timer_svc_->process_expired();
397   397  
HITCBC 398   219780 ready_queue local_ops; 398   235775 ready_queue local_ops;
399   399  
HITCBC 400   219780 if (ready > 0) 400   235775 if (ready > 0)
401   { 401   {
HITCBC 402   205203 if (FD_ISSET(pipe_fds_[0], &read_fds)) 402   220942 if (FD_ISSET(pipe_fds_[0], &read_fds))
403   { 403   {
404   char buf[256]; 404   char buf[256];
HITCBC 405   9116 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0) 405   9234 while (::read(pipe_fds_[0], buf, sizeof(buf)) > 0)
406   { 406   {
407   } 407   }
408   } 408   }
409   409  
HITCBC 410   509075 for (int i = 0; i < snapshot_count; ++i) 410   554879 for (int i = 0; i < snapshot_count; ++i)
411   { 411   {
HITCBC 412   303872 int fd = snapshot[i].fd; 412   333937 int fd = snapshot[i].fd;
HITCBC 413   303872 reactor_descriptor_state* desc = snapshot[i].desc; 413   333937 reactor_descriptor_state* desc = snapshot[i].desc;
414   414  
HITCBC 415   303872 std::uint32_t flags = 0; 415   333937 std::uint32_t flags = 0;
HITCBC 416   303872 if (FD_ISSET(fd, &read_fds)) 416   333937 if (FD_ISSET(fd, &read_fds))
HITCBC 417   202838 flags |= reactor_event_read; 417   218546 flags |= reactor_event_read;
HITCBC 418   303872 if (FD_ISSET(fd, &write_fds)) 418   333937 if (FD_ISSET(fd, &write_fds))
HITCBC 419   2042 flags |= reactor_event_write; 419   2070 flags |= reactor_event_write;
HITCBC 420   303872 if (FD_ISSET(fd, &except_fds)) 420   333937 if (FD_ISSET(fd, &except_fds))
MISUBC 421   ✗ flags |= reactor_event_error; 421   ✗ flags |= reactor_event_error;
422   422  
HITCBC 423   303872 if (flags == 0) 423   333937 if (flags == 0)
HITCBC 424   99003 continue; 424   113332 continue;
425   425  
HITCBC 426   204869 desc->add_ready_events(flags); 426   220605 desc->add_ready_events(flags);
427   427  
HITCBC 428   204869 bool expected = false; 428   220605 bool expected = false;
HITCBC 429   204869 if (desc->is_enqueued_.compare_exchange_strong( 429   220605 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   204869 local_ops.push(desc); 433   220605 local_ops.push(desc);
434   } 434   }
435   } 435   }
436   } 436   }
437   437  
HITCBC 438   219780 lock.lock(); 438   235775 lock.lock();
439   439  
HITCBC 440   219780 completed_ops_.splice(local_ops); 440   235775 completed_ops_.splice(local_ops);
HITCBC 441   219780 } 441   235775 }
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