TLA  Line data    Source code

       1                 : //
       2                 : // Copyright (c) 2026 Michael Vandeberg
       3                 : //
       4                 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
       5                 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
       6                 : //
       7                 : // Official repository: https://github.com/cppalliance/corosio
       8                 : //
       9                 : 
      10                 : #ifndef BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SIGNAL_PIPE_HPP
      11                 : #define BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SIGNAL_PIPE_HPP
      12                 : 
      13                 : #include <boost/corosio/detail/platform.hpp>
      14                 : 
      15                 : #if BOOST_COROSIO_POSIX
      16                 : 
      17                 : #include <boost/corosio/native/detail/posix/posix_signal_service.hpp>
      18                 : #include <boost/corosio/native/detail/reactor/reactor_descriptor_state.hpp>
      19                 : #include <boost/corosio/native/detail/reactor/reactor_op_base.hpp>
      20                 : 
      21                 : #include <errno.h>
      22                 : 
      23                 : /*
      24                 :     Reactor signal-pipe reader
      25                 :     ==========================
      26                 : 
      27                 :     Bridges the global POSIX signal self-pipe (see posix_signal_service.hpp)
      28                 :     to the reactor backends (epoll/kqueue/select). The concrete scheduler owns
      29                 :     one of these for its lifetime and, in register_signal_reader(), parks the
      30                 :     drain op as the descriptor's read_op then calls register_descriptor().
      31                 : 
      32                 :     The drain op never completes: on each read-readiness edge, invoke_deferred_io
      33                 :     calls perform_io(), which drains the pipe and delivers the pending signals,
      34                 :     then reports EAGAIN so the op stays parked and re-fires on the next edge —
      35                 :     exactly the path a socket read op takes when the kernel has no more data.
      36                 :     Because deliver_signal() runs here, in normal dispatch context (not in the
      37                 :     signal handler and not under the reactor poll lock), its mutex locking is
      38                 :     safe.
      39                 : */
      40                 : 
      41                 : namespace boost::corosio::detail {
      42                 : 
      43                 : struct reactor_signal_pipe_reader
      44                 : {
      45                 :     // Parked read op: drains the self-pipe and re-arms via EAGAIN.
      46                 :     struct drain_op final : reactor_op_base
      47                 :     {
      48 HIT         300 :         void perform_io() noexcept override
      49                 :         {
      50             300 :             posix_signal_detail::drain_signal_pipe();
      51                 :             // Stay parked: EAGAIN tells invoke_deferred_io to keep this op
      52                 :             // installed as read_op and re-run it on the next readiness edge.
      53             300 :             errn = EAGAIN;
      54             300 :         }
      55                 :     };
      56                 : 
      57                 :     reactor_descriptor_state desc;
      58                 :     drain_op                 op;
      59                 : 
      60                 :     // Park the drain op and return the descriptor to hand to
      61                 :     // scheduler::register_descriptor(read_fd, ...).
      62              82 :     reactor_descriptor_state* arm() noexcept
      63                 :     {
      64              82 :         desc.read_op = &op;
      65              82 :         return &desc;
      66                 :     }
      67                 : };
      68                 : 
      69                 : } // namespace boost::corosio::detail
      70                 : 
      71                 : #endif // BOOST_COROSIO_POSIX
      72                 : 
      73                 : #endif // BOOST_COROSIO_NATIVE_DETAIL_REACTOR_REACTOR_SIGNAL_PIPE_HPP