os-core.cpp

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/*
 * This file is part of the µOS++ project (https://micro-os-plus.github.io/).
 * Copyright (c) 2016-2025 Liviu Ionescu. All rights reserved.
 *
 * Permission to use, copy, modify, and/or distribute this software
 * for any purpose is hereby granted, under the terms of the MIT license.
 *
 * If a copy of the license was not distributed with this file, it can
 * be obtained from https://opensource.org/licenses/mit.
 */
 
#if defined(OS_USE_OS_APP_CONFIG_H)
#include <cmsis-plus/os-app-config.h>
#endif
 
#include <cmsis-plus/rtos/os.h>
 
// ----------------------------------------------------------------------------
 
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wc++98-compat"
#endif
 
// ----------------------------------------------------------------------------
 
namespace
{
#if defined(OS_HAS_INTERRUPTS_STACK)
  // Object used to manage the interrupts stack.
  class os::rtos::thread::stack interrupts_stack;
#endif /* defined(OS_HAS_INTERRUPTS_STACK) */
} // namespace
 
namespace os
{
  namespace rtos
  {
 
    namespace scheduler
    {
      bool is_started_ = false;
 
#if 0
      state_t lock_state_ = state::init;
#endif
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wglobal-constructors"
#pragma clang diagnostic ignored "-Wexit-time-destructors"
#endif
      // top_threads_list top_threads_list_;
      thread::threads_list top_threads_list_;
 
#pragma GCC diagnostic pop
 
#if !defined(OS_USE_RTOS_PORT_SCHEDULER)
 
      bool is_preemptive_ = false;
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wpadded"
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Wpadded"
#endif
      // A small kludge to provide a temporary errno before
      // the first real thread is created.
      typedef struct
      {
        void* vtbl;
        void* name_;
        // errno is the first thread member, so right after the name.
        int errno_;
      } tiny_thread_t;
#pragma GCC diagnostic pop
 
      // Ensure the tiny thread is large enough to have the errno
      // member in the same location.
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Winvalid-offsetof"
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Winvalid-offsetof"
#endif
      static_assert (offsetof (tiny_thread_t, errno_)
                         == offsetof (thread, errno_),
                     "adjust tiny_thread_t members");
#pragma GCC diagnostic pop
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wmissing-variable-declarations"
#endif
      tiny_thread_t tiny_thread;
#pragma GCC diagnostic pop
 
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
      thread* volatile current_thread_
          = reinterpret_cast<thread*> (&tiny_thread);
#pragma GCC diagnostic pop
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wglobal-constructors"
#pragma clang diagnostic ignored "-Wexit-time-destructors"
#endif
      internal::ready_threads_list ready_threads_list_;
#pragma GCC diagnostic pop
#endif
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wglobal-constructors"
#pragma clang diagnostic ignored "-Wexit-time-destructors"
#endif
      internal::terminated_threads_list terminated_threads_list_;
#pragma GCC diagnostic pop
 
      result_t
      initialize (void)
      {
#if defined(OS_TRACE_RTOS_SCHEDULER)
        trace::printf ("scheduler::%s() \n", __func__);
#endif
 
        // Don't call this from interrupt handlers.
        os_assert_err (!interrupts::in_handler_mode (), EPERM);
 
#if defined(OS_USE_RTOS_PORT_SCHEDULER)
 
        return port::scheduler::initialize ();
 
#else
 
        port::scheduler::initialize ();
 
        return result::ok;
#endif
      }
 
      [[noreturn]] void
      start (void)
      {
        trace::printf ("scheduler::%s() \n", __func__);
 
        // Don't call this from interrupt handlers.
        os_assert_throw (!interrupts::in_handler_mode (), EPERM);
 
        sysclock.start ();
        hrclock.start ();
 
        rtclock.start ();
 
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES)
 
        scheduler::statistics::context_switches_ = 0;
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES) */
 
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES)
 
        scheduler::statistics::cpu_cycles_ = 0;
        scheduler::statistics::switch_timestamp_ = hrclock.now ();
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES) */
 
#if !defined(OS_USE_RTOS_PORT_SCHEDULER)
        is_preemptive_ = OS_BOOL_RTOS_SCHEDULER_PREEMPTIVE;
#endif /* defined(OS_USE_RTOS_PORT_SCHEDULER) */
 
        is_started_ = true;
 
        port::scheduler::start ();
      }
 
      bool
      preemptive (bool state)
      {
#if defined(OS_TRACE_RTOS_SCHEDULER)
        trace::printf ("scheduler::%s(%d) \n", __func__, state);
#endif
        // Don't call this from interrupt handlers.
        os_assert_throw (!interrupts::in_handler_mode (), EPERM);
 
#if defined(OS_USE_RTOS_PORT_SCHEDULER)
 
        return port::scheduler::preemptive (state);
 
#else
        bool tmp;
 
        {
          // ----- Enter critical section -------------------------------------
          interrupts::critical_section ics;
 
          tmp = is_preemptive_;
          is_preemptive_ = state;
          // ----- Exit critical section --------------------------------------
        }
 
        return tmp;
#endif
      }
 
      thread::threads_list&
      children_threads (thread* th)
      {
        if (th == nullptr)
          {
            return top_threads_list_;
          }
        else
          {
            return th->children_;
          }
      }
 
      /*
       * @var const state_t critical_section::state_
 
       * @details
       * The variable is constant, after being set by the constructor no
       * further changes are possible.
       *
       * The variable type usually is a `bool`, but a counter is also
       * possible if the scheduler uses a recursive lock.
       */
 
    } /* namespace scheduler */
 
    namespace scheduler
    {
      void
      internal_link_node (internal::waiting_threads_list& list,
                          internal::waiting_thread_node& node)
      {
        // Remove this thread from the ready list, if there.
        port::this_thread::prepare_suspend ();
 
        // Add this thread to the node waiting list.
        list.link (node);
        node.thread_->waiting_node_ = &node;
 
        node.thread_->state_ = thread::state::suspended;
      }
 
      void
      internal_unlink_node (internal::waiting_thread_node& node)
      {
        {
          // ----- Enter critical section -------------------------------------
          interrupts::critical_section ics;
 
          // Remove the thread from the node waiting list,
          // if not already removed.
          node.thread_->waiting_node_ = nullptr;
          node.unlink ();
          // ----- Exit critical section --------------------------------------
        }
      }
 
      void
      internal_link_node (internal::waiting_threads_list& list,
                          internal::waiting_thread_node& node,
                          internal::clock_timestamps_list& timeout_list,
                          internal::timeout_thread_node& timeout_node)
      {
        // Remove this thread from the ready list, if there.
        port::this_thread::prepare_suspend ();
 
        // Add this thread to the node waiting list.
        list.link (node);
        node.thread_->waiting_node_ = &node;
 
        node.thread_->state_ = thread::state::suspended;
 
        // Add this thread to the clock timeout list.
        timeout_list.link (timeout_node);
        timeout_node.thread.clock_node_ = &timeout_node;
      }
 
      void
      internal_unlink_node (internal::waiting_thread_node& node,
                            internal::timeout_thread_node& timeout_node)
      {
        // ----- Enter critical section ---------------------------------------
        interrupts::critical_section ics;
 
        // Remove the thread from the clock timeout list,
        // if not already removed by the timer.
        timeout_node.thread.clock_node_ = nullptr;
        timeout_node.unlink ();
 
        // Remove the thread from the node waiting list,
        // if not already removed.
        node.thread_->waiting_node_ = nullptr;
        node.unlink ();
        // ----- Exit critical section ----------------------------------------
      }
 
      // ----------------------------------------------------------------------
 
#if !defined(OS_USE_RTOS_PORT_SCHEDULER)
 
      void
      internal_switch_threads (void)
      {
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES)
 
        // Get the high resolution timestamp.
        clock::timestamp_t now = hrclock.now ();
 
#pragma GCC diagnostic push
#if defined(__clang__)
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Wuseless-cast"
#endif
 
        // Compute duration since previous context switch.
        // Assume scheduler is not disabled for very long.
        rtos::statistics::duration_t delta
            = static_cast<rtos::statistics::duration_t> (
                now - scheduler::statistics::switch_timestamp_);
 
#pragma GCC diagnostic pop
 
        // Accumulate durations to scheduler total.
        scheduler::statistics::cpu_cycles_ += delta;
 
        // Accumulate durations to old thread.
        scheduler::current_thread_->statistics_.cpu_cycles_ += delta;
 
        // Remember the timestamp for the next context switch.
        scheduler::statistics::switch_timestamp_ = now;
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES) */
 
        // The very core of the scheduler, if not locked, re-link the
        // current thread and return the top priority thread.
        if (!locked ())
          {
            // Normally the old running thread must be re-linked to ready.
            scheduler::current_thread_->internal_relink_running_ ();
 
            // The top of the ready list gives the next thread to run.
            scheduler::current_thread_
                = scheduler::ready_threads_list_.unlink_head ();
          }
 
          // ***** Pointer switched to new thread! *****
 
          // The new thread was marked as running in unlink_head(),
          // so in case the handler is re-entered immediately,
          // the relink_running() will simply reschedule it,
          // otherwise the thread will be lost.
 
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES)
 
        // Increment global context switches.
        scheduler::statistics::context_switches_++;
 
        // Increment new thread context switches.
        scheduler::current_thread_->statistics_.context_switches_++;
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES) */
      }
 
#endif /* !defined(OS_USE_RTOS_PORT_SCHEDULER) */
 
      namespace statistics
      {
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES)
 
        rtos::statistics::counter_t context_switches_;
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CONTEXT_SWITCHES) */
 
#if defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES)
 
        clock::timestamp_t switch_timestamp_;
        rtos::statistics::duration_t cpu_cycles_;
 
#endif /* defined(OS_INCLUDE_RTOS_STATISTICS_THREAD_CPU_CYCLES) */
 
      } /* namespace statistics */
 
    } /* namespace scheduler */
 
    namespace interrupts
    {
      /*
       * @var const state_t critical_section::state_
 
       * @details
       * The variable is constant, after being set by the constructor no
       * further changes are possible.
       *
       * The variable type usually is an unsigned integer where
       * the priorities register is saved.
       */
 
      /*
       * @var state_t lockable::state_
 
       * @details
       * The variable type usually is an unsigned integer where
       * the priorities register is saved.
       */
 
#if defined(OS_HAS_INTERRUPTS_STACK) || defined(__DOXYGEN__)
 
      class thread::stack*
      stack (void)
      {
        return &interrupts_stack;
      }
 
#endif /* defined(OS_HAS_INTERRUPTS_STACK) */
 
    } /* namespace interrupts */
 
    // ========================================================================
    namespace internal
    {
      /*
       * @var const char* const object_named::name_
 
       * @details
       * To save space, the null terminated string passed to the
       * constructor is not copied locally. Instead, the pointer to
       * the string is copied, so the
       * caller must ensure that the pointer life cycle
       * is at least as long as the object life cycle. A constant
       * string (stored in flash) is preferred.
       */
 
      object_named::object_named ()
      {
      }
 
      object_named::object_named (const char* name)
          : name_ (name != nullptr ? name : "-")
      {
      }
 
    } /* namespace internal */
 
    // ========================================================================
  } /* namespace rtos */
} /* namespace os */
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wreserved-identifier"
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Wredundant-decls"
#endif
int*
__errno (void);
#pragma GCC diagnostic pop
 
int*
__errno (void)
{
  return os::rtos::this_thread::__errno ();
}
 
// ----------------------------------------------------------------------------