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diff --git a/c-user/config/idle-task.rst b/c-user/config/idle-task.rst new file mode 100644 index 0000000..793fb5c --- /dev/null +++ b/c-user/config/idle-task.rst @@ -0,0 +1,260 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 2020, 2022 embedded brains GmbH & Co. KG +.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR) + +.. This file is part of the RTEMS quality process and was automatically +.. generated. If you find something that needs to be fixed or +.. worded better please post a report or patch to an RTEMS mailing list +.. or raise a bug report: +.. +.. https://www.rtems.org/bugs.html +.. +.. For information on updating and regenerating please refer to the How-To +.. section in the Software Requirements Engineering chapter of the +.. RTEMS Software Engineering manual. The manual is provided as a part of +.. a release. For development sources please refer to the online +.. documentation at: +.. +.. https://docs.rtems.org + +.. Generated from spec:/acfg/if/group-idle + +Idle Task Configuration +======================= + +This section describes configuration options related to the idle tasks. + +.. Generated from spec:/acfg/if/idle-task-body + +.. raw:: latex + + \clearpage + +.. index:: CONFIGURE_IDLE_TASK_BODY + +.. _CONFIGURE_IDLE_TASK_BODY: + +CONFIGURE_IDLE_TASK_BODY +------------------------ + +.. rubric:: CONSTANT: + +``CONFIGURE_IDLE_TASK_BODY`` + +.. rubric:: OPTION TYPE: + +This configuration option is an initializer define. + +.. rubric:: DEFAULT VALUE: + +If the :ref:`CONFIGURE_DISABLE_BSP_SETTINGS` configuration option is not defined and +:c:macro:`BSP_IDLE_TASK_BODY` is provided by the +:term:`BSP`, then the default value is defined by +:c:macro:`BSP_IDLE_TASK_BODY`, otherwise the default value is +``_CPU_Thread_Idle_body``. + +.. rubric:: DESCRIPTION: + +The value of this configuration option initializes the IDLE thread body. + +.. rubric:: NOTES: + +IDLE threads shall not block. A blocking IDLE thread results in undefined +system behaviour because the scheduler assume that at least one ready thread +exists. + +IDLE threads can be used to initialize the application, see configuration +option :ref:`CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`. + +The BSP may have knowledge of the specific CPU model, system controller +logic, and peripheral buses, so a BSP-specific IDLE task may be capable of +turning components off to save power during extended periods of no task +activity. + +.. rubric:: CONSTRAINTS: + +The value of the configuration option shall be defined to a valid function +pointer of the type ``void *( *idle_body )( uintptr_t )``. + +.. Generated from spec:/acfg/if/idle-task-init-appl + +.. raw:: latex + + \clearpage + +.. index:: CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION + +.. _CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION: + +CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION +------------------------------------------- + +.. rubric:: CONSTANT: + +``CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`` + +.. rubric:: OPTION TYPE: + +This configuration option is a boolean feature define. + +.. rubric:: DEFAULT CONFIGURATION: + +If this configuration option is undefined, then the user is assumed to +provide one or more initialization tasks. + +.. rubric:: DESCRIPTION: + +This configuration option is defined to indicate that the user has configured +**no** user initialization tasks or threads and that the user provided IDLE +task will perform application initialization and then transform itself into +an IDLE task. + +.. rubric:: NOTES: + +If you use this option be careful, the user IDLE task **cannot** block at all +during the initialization sequence. Further, once application +initialization is complete, it shall make itself preemptible and enter an idle +body loop. + +The IDLE task shall run at the lowest priority of all tasks in the system. + +If this configuration option is defined, then it is mandatory to configure a +user IDLE task with the :ref:`CONFIGURE_IDLE_TASK_BODY` configuration option, +otherwise a compile time error in the configuration file will occur. + +The application shall define at least one of the following configuration +options + +* :ref:`CONFIGURE_RTEMS_INIT_TASKS_TABLE`, + +* :ref:`CONFIGURE_POSIX_INIT_THREAD_TABLE`, or + +* ``CONFIGURE_IDLE_TASK_INITIALIZES_APPLICATION`` + +otherwise a compile time error in the configuration file will occur. + +If no Classic API initialization task and no POSIX API initialization thread +is configured, then no :ref:`GlobalConstruction` is performed. + +.. Generated from spec:/acfg/if/idle-task-stack-size + +.. raw:: latex + + \clearpage + +.. index:: CONFIGURE_IDLE_TASK_STACK_SIZE + +.. _CONFIGURE_IDLE_TASK_STACK_SIZE: + +CONFIGURE_IDLE_TASK_STACK_SIZE +------------------------------ + +.. rubric:: CONSTANT: + +``CONFIGURE_IDLE_TASK_STACK_SIZE`` + +.. rubric:: OPTION TYPE: + +This configuration option is an integer define. + +.. rubric:: DEFAULT VALUE: + +If the :ref:`CONFIGURE_DISABLE_BSP_SETTINGS` configuration option is not defined and +:c:macro:`BSP_IDLE_TASK_STACK_SIZE` is provided by the +:term:`BSP`, then the default value is defined by +:c:macro:`BSP_IDLE_TASK_STACK_SIZE`, otherwise the default value is +defined by the :ref:`CONFIGURE_MINIMUM_TASK_STACK_SIZE` configuration option. + +.. rubric:: DESCRIPTION: + +The value of this configuration option defines the task stack size for an +IDLE task. + +.. rubric:: NOTES: + +In SMP configurations, there is one IDLE task per configured processor, see +:ref:`CONFIGURE_MAXIMUM_PROCESSORS`. + +.. rubric:: CONSTRAINTS: + +The following constraints apply to this configuration option: + +* The value of the configuration option shall be greater than or equal to a + BSP-specific and application-specific minimum value. + +* The value of the configuration option shall be small enough so that the IDLE + task stack area calculation carried out by ``<rtems/confdefs.h>`` does not + overflow an integer of type `size_t + <https://en.cppreference.com/w/c/types/size_t>`_. + +.. Generated from spec:/acfg/if/idle-task-storage-size + +.. raw:: latex + + \clearpage + +.. index:: CONFIGURE_IDLE_TASK_STORAGE_SIZE +.. index:: IDLE task storage size + +.. _CONFIGURE_IDLE_TASK_STORAGE_SIZE: + +CONFIGURE_IDLE_TASK_STORAGE_SIZE +-------------------------------- + +.. rubric:: CONSTANT: + +``CONFIGURE_IDLE_TASK_STORAGE_SIZE`` + +.. rubric:: OPTION TYPE: + +This configuration option is an integer define. + +.. rubric:: DEFAULT VALUE: + +This configuration option has no default value. If it is not specified, then +the task storage area for each :term:`IDLE task` will allocated +from the RTEMS Workspace or through a custom IDLE task stack allocator. + +.. rubric:: DESCRIPTION: + +If this configuration option is specified, then the task storage areas for +the :term:`IDLE tasks <IDLE task>` are statically allocated by +``<rtems/confdefs.h>``. The value of this configuration option defines the +size in bytes of the task storage area of each IDLE task in the system. + +.. rubric:: NOTES: + +By default, the IDLE task storage areas are allocated from the RTEMS +Workspace. Applications which do not want to use a heap allocator can use +this configuration option to use statically allocated memory for the IDLE +task storage areas. The task storage area contains the task stack, the +thread-local storage, and the floating-point context on architectures with a +separate floating-point context. The size of the thread-local storage area +is defined at link time or by the :ref:`CONFIGURE_MAXIMUM_THREAD_LOCAL_STORAGE_SIZE` +configuration option. You have to estimate the actual thread-local storage +size if you want to use this configuration option. If the IDLE task stack +size would be less than the value defined by the +:ref:`CONFIGURE_IDLE_TASK_STACK_SIZE` configuration option, for example because the +thread-local storage size is larger than expected, then the system terminates +with the :ref:`INTERNAL_ERROR_CORE <FatalErrorSources>` fatal source and the +:ref:`INTERNAL_ERROR_IDLE_THREAD_STACK_TOO_SMALL <internal_errors>` fatal code during +system initialization. + +The value of this configuration option is passed to +:ref:`InterfaceRTEMSTASKSTORAGESIZE` by ``<rtems/confdefs.h>`` to determine +the actual size of the statically allocated area to take +architecture-specific overheads into account. + +The + +* ``CONFIGURE_IDLE_TASK_STORAGE_SIZE``, and + +* :ref:`CONFIGURE_TASK_STACK_ALLOCATOR_FOR_IDLE` + +configuration options are mutually exclusive. + +.. rubric:: CONSTRAINTS: + +The value of the configuration option shall be greater than or equal to +:ref:`CONFIGURE_IDLE_TASK_STACK_SIZE`. |