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Try to bring all descriptions up to date. Add cross-references to several options. Clarify configuration value constraints. Use this template also for initializer type options. Close #3901.
123 lines
3.8 KiB
ReStructuredText
123 lines
3.8 KiB
ReStructuredText
.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
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.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
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Idle Task Configuration
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=======================
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This section describes configuration options related to the idle tasks.
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.. index:: CONFIGURE_IDLE_TASK_BODY
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.. _CONFIGURE_IDLE_TASK_BODY:
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CONFIGURE_IDLE_TASK_BODY
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------------------------
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CONSTANT:
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``CONFIGURE_IDLE_TASK_BODY``
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OPTION TYPE:
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This configuration option is an initializer define.
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DEFAULT VALUE:
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If :ref:`BSP_IDLE_TASK_BODY` is defined, then this will be the default value,
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otherwise the default value is ``_CPU_Thread_Idle_body``.
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VALUE CONSTRAINTS:
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The value of this configuration option shall be defined to a valid function
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pointer of the type ``void *( *idle_body )( uintptr_t )``.
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DESCRIPTION:
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The value of this configuration option initializes the IDLE thread body.
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NOTES:
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IDLE threads shall not block. A blocking IDLE thread results in undefined
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system behaviour because the scheduler assume that at least one ready thread
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exists.
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IDLE threads can be used to initialize the application, see configuration
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option :ref:`CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`.
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.. index:: CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION
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.. _CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION:
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CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION
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-------------------------------------------
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CONSTANT:
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``CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION``
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OPTION TYPE:
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This configuration option is a boolean feature define.
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DEFAULT CONFIGURATION:
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If this configuration option is undefined, then the user is assumed to
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provide one or more initialization tasks.
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DESCRIPTION:
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This configuration option is defined to indicate that the user has configured
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**no** user initialization tasks or threads and that the user provided IDLE
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task will perform application initialization and then transform itself into
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an IDLE task.
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NOTES:
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If you use this option be careful, the user IDLE task **cannot** block at all
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during the initialization sequence. Further, once application
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initialization is complete, it shall make itself preemptible and enter an idle
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body loop.
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The IDLE task shall run at the lowest priority of all tasks in the system.
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If this configuration option is defined, then it is mandatory to configure a
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user IDLE task with the :ref:`CONFIGURE_IDLE_TASK_BODY` configuration option,
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otherwise a compile time error in the configuration file will occur.
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The application shall define exactly one of the following configuration
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options
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* :ref:`CONFIGURE_RTEMS_INIT_TASKS_TABLE`,
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* :ref:`CONFIGURE_POSIX_INIT_THREAD_TABLE`, or
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* `CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`
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otherwise a compile time error in the configuration file will occur.
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.. index:: CONFIGURE_IDLE_TASK_STACK_SIZE
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.. _CONFIGURE_IDLE_TASK_STACK_SIZE:
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CONFIGURE_IDLE_TASK_STACK_SIZE
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------------------------------
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CONSTANT:
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``CONFIGURE_IDLE_TASK_STACK_SIZE``
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OPTION TYPE:
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This configuration option is an integer define.
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DEFAULT VALUE:
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The default value is :ref:`CONFIGURE_MINIMUM_TASK_STACK_SIZE`.
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VALUE CONSTRAINTS:
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The value of this configuration option shall satisfy all of the following
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constraints:
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* It shall be greater than or equal to a
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BSP-specific and application-specific minimum value.
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* It shall be small enough so that the IDLE
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task stack area calculation carried out by ``<rtems/confdefs.h>`` does not
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overflow an integer of type ``size_t``.
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DESCRIPTION:
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The value of this configuration option defines the task stack size for an
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IDLE task.
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NOTES:
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In SMP configurations, there is one IDLE task per configured processor, see
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:ref:`CONFIGURE_MAXIMUM_PROCESSORS`.
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