os-idle.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
 
// ----------------------------------------------------------------------------
 
using namespace os;
using namespace os::rtos;
 
// ----------------------------------------------------------------------------
 
void*
os_idle (thread::func_args_t args);
 
// os-thread.h
// void
// os_rtos_idle_actions (void);
 
bool __attribute__ ((weak))
os_rtos_idle_enter_power_saving_mode_hook (void)
{
  return false;
}
 
void __attribute__ ((weak))
os_rtos_idle_actions (void)
{
  while (!scheduler::terminated_threads_list_.empty ())
    {
      internal::waiting_thread_node* node;
      {
        // ----- Enter critical section ---------------------------------------
        interrupts::critical_section ics;
        node = const_cast<internal::waiting_thread_node*> (
            scheduler::terminated_threads_list_.head ());
        node->unlink ();
        // ----- Exit critical section ----------------------------------------
      }
      node->thread_->internal_destroy_ ();
 
      this_thread::yield ();
    }
 
#if defined(OS_HAS_INTERRUPTS_STACK)
  // Simple test to verify that the interrupts
  // did not underflow the stack.
  assert (rtos::interrupts::stack ()->check_bottom_magic ());
#endif
 
  if (!os_rtos_idle_enter_power_saving_mode_hook ())
    {
      port::scheduler::wait_for_interrupt ();
    }
}
 
#if !defined(OS_USE_RTOS_PORT_SCHEDULER) || defined(__DOXYGEN__)
 
extern thread* os_idle_thread;
 
thread* os_idle_thread;
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wexit-time-destructors"
#pragma clang diagnostic ignored "-Wglobal-constructors"
#pragma clang diagnostic ignored "-Wmissing-variable-declarations"
#endif
 
#if defined(OS_EXCLUDE_DYNAMIC_MEMORY_ALLOCATIONS)
 
static thread_inclusive<OS_INTEGER_RTOS_IDLE_STACK_SIZE_BYTES> os_idle_thread_{
  "idle", os_idle, nullptr
};
 
#else
 
static std::unique_ptr<thread> os_idle_thread_;
 
#endif /* defined(OS_EXCLUDE_DYNAMIC_MEMORY_ALLOCATIONS) */
 
#pragma GCC diagnostic pop
 
void __attribute__ ((weak))
os_startup_create_thread_idle (void)
{
#if defined(OS_EXCLUDE_DYNAMIC_MEMORY_ALLOCATIONS)
 
  // The thread object instance was created by the static constructors.
  os_idle_thread = &os_idle_thread_;
 
#else
 
  thread::attributes attr = thread::initializer;
  attr.th_stack_size_bytes = OS_INTEGER_RTOS_IDLE_STACK_SIZE_BYTES;
 
  // No need for an explicit delete, it is deallocated by the unique_ptr.
  os_idle_thread_
      = std::unique_ptr<thread> (new thread ("idle", os_idle, nullptr, attr));
 
  os_idle_thread = os_idle_thread_.get ();
 
#endif /* defined(OS_EXCLUDE_DYNAMIC_MEMORY_ALLOCATIONS) */
}
 
void*
os_idle (thread::func_args_t args __attribute__ ((unused)))
{
 
  // The thread was created with the default priority, and the
  // idle thread must run with th lowest possible priority.
 
#if defined(OS_BOOL_RTOS_THREAD_IDLE_PRIORITY_BELOW_IDLE)
  // The CMSIS RTOS validator creates threads with `priority::idle`,
  // so, to be sure that the system idle thread has the lowest priority,
  // go one step below the idle priority.
  this_thread::thread ().priority (thread::priority::idle - 1);
#else
  this_thread::thread ().priority (thread::priority::idle);
#endif
 
  while (true)
    {
      os_rtos_idle_actions ();
 
      // Possibly switch to threads that were resumed during sleep.
      this_thread::yield ();
    }
}
 
#endif /* !defined(OS_USE_RTOS_PORT_SCHEDULER) */
 
// ----------------------------------------------------------------------------