.. SPDX-License-Identifier: CC-BY-SA-4.0 .. Copyright (C) 2020, 2021 embedded brains GmbH (http://www.embedded-brains.de) .. 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 .. _BarrierManagerDirectives: Directives ========== This section details the directives of the Barrier Manager. A subsection is dedicated to each of this manager's directives and lists the calling sequence, parameters, description, return values, and notes of the directive. .. Generated from spec:/rtems/barrier/if/create .. raw:: latex \clearpage .. index:: rtems_barrier_create() .. index:: create a barrier .. _InterfaceRtemsBarrierCreate: rtems_barrier_create() ---------------------- Creates a barrier. .. rubric:: CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_barrier_create( rtems_name name, rtems_attribute attribute_set, uint32_t maximum_waiters, rtems_id *id ); .. rubric:: PARAMETERS: ``name`` This parameter is the object name of the barrier. ``attribute_set`` This parameter is the attribute set of the barrier. ``maximum_waiters`` This parameter is the maximum count of waiters on an automatic release barrier. ``id`` This parameter is the pointer to an object identifier variable. When the directive call is successful, the identifier of the created barrier will be stored in this variable. .. rubric:: DESCRIPTION: This directive creates a barrier which resides on the local node. The barrier has the user-defined object name specified in ``name`` and the initial count specified in ``attribute_set``. The assigned object identifier is returned in ``id``. This identifier is used to access the barrier with other barrier related directives. The **attribute set** specified in ``attribute_set`` is built through a *bitwise or* of the attribute constants described below. Not all combinations of attributes are allowed. Some attributes are mutually exclusive. If mutually exclusive attributes are combined, the behaviour is undefined. Attributes not mentioned below are not evaluated by this directive and have no effect. Default attributes can be selected by using the :c:macro:`RTEMS_DEFAULT_ATTRIBUTES` constant. The **barrier class** is selected by the mutually exclusive :c:macro:`RTEMS_BARRIER_MANUAL_RELEASE` and :c:macro:`RTEMS_BARRIER_AUTOMATIC_RELEASE` attributes. * The **manual release class** is the default and can be emphasized through use of the :c:macro:`RTEMS_BARRIER_MANUAL_RELEASE` attribute. For this class, there is no limit on the number of tasks that will block at the barrier. Only when the :ref:`InterfaceRtemsBarrierRelease` directive is invoked, are the tasks waiting at the barrier unblocked. * The **automatic release class** is selected by the :c:macro:`RTEMS_BARRIER_AUTOMATIC_RELEASE` attribute. For this class, tasks calling the :ref:`InterfaceRtemsBarrierWait` directive will block until there are ``maximum_waiters`` minus one tasks waiting at the barrier. When the ``maximum_waiters`` task invokes the :ref:`InterfaceRtemsBarrierWait` directive, the previous ``maximum_waiters`` - 1 tasks are automatically released and the caller returns. .. rubric:: RETURN VALUES: :c:macro:`RTEMS_SUCCESSFUL` The requested operation was successful. :c:macro:`RTEMS_INVALID_NAME` The ``name`` parameter was invalid. :c:macro:`RTEMS_INVALID_ADDRESS` The ``id`` parameter was `NULL `_. :c:macro:`RTEMS_INVALID_NUMBER` The ``maximum_waiters`` parameter was 0 for an automatic release barrier. :c:macro:`RTEMS_TOO_MANY` There was no inactive object available to create a barrier. The number of barriers available to the application is configured through the :ref:`CONFIGURE_MAXIMUM_BARRIERS` application configuration option. .. rubric:: NOTES: For control and maintenance of the barrier, RTEMS allocates a :term:`BCB` from the local BCB free pool and initializes it. .. rubric:: CONSTRAINTS: The following constraints apply to this directive: * The directive may be called from within device driver initialization context. * The directive may be called from within task context. * The directive may obtain and release the object allocator mutex. This may cause the calling task to be preempted. * The number of barriers available to the application is configured through the :ref:`CONFIGURE_MAXIMUM_BARRIERS` application configuration option. * Where the object class corresponding to the directive is configured to use unlimited objects, the directive may allocate memory from the RTEMS Workspace. .. Generated from spec:/rtems/barrier/if/ident .. raw:: latex \clearpage .. index:: rtems_barrier_ident() .. _InterfaceRtemsBarrierIdent: rtems_barrier_ident() --------------------- Identifies a barrier by the object name. .. rubric:: CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_barrier_ident( rtems_name name, rtems_id *id ); .. rubric:: PARAMETERS: ``name`` This parameter is the object name to look up. ``id`` This parameter is the pointer to an object identifier variable. When the directive call is successful, the object identifier of an object with the specified name will be stored in this variable. .. rubric:: DESCRIPTION: This directive obtains a barrier identifier associated with the barrier name specified in ``name``. .. rubric:: RETURN VALUES: :c:macro:`RTEMS_SUCCESSFUL` The requested operation was successful. :c:macro:`RTEMS_INVALID_ADDRESS` The ``id`` parameter was `NULL `_. :c:macro:`RTEMS_INVALID_NAME` The ``name`` parameter was 0. :c:macro:`RTEMS_INVALID_NAME` There was no object with the specified name on the local node. .. rubric:: NOTES: If the barrier name is not unique, then the barrier identifier will match the first barrier with that name in the search order. However, this barrier identifier is not guaranteed to correspond to the desired barrier. The objects are searched from lowest to the highest index. Only the local node is searched. The barrier identifier is used with other barrier related directives to access the barrier. .. rubric:: CONSTRAINTS: The following constraints apply to this directive: * The directive may be called from within any runtime context. * The directive will not cause the calling task to be preempted. .. Generated from spec:/rtems/barrier/if/delete .. raw:: latex \clearpage .. index:: rtems_barrier_delete() .. index:: delete a barrier .. _InterfaceRtemsBarrierDelete: rtems_barrier_delete() ---------------------- Deletes the barrier. .. rubric:: CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_barrier_delete( rtems_id id ); .. rubric:: PARAMETERS: ``id`` This parameter is the barrier identifier. .. rubric:: DESCRIPTION: This directive deletes the barrier specified by ``id``. All tasks blocked waiting for the barrier to be released will be readied and returned a status code which indicates that the barrier was deleted. .. rubric:: RETURN VALUES: :c:macro:`RTEMS_SUCCESSFUL` The requested operation was successful. :c:macro:`RTEMS_INVALID_ID` There was no barrier associated with the identifier specified by ``id``. .. rubric:: NOTES: The :term:`BCB` for the deleted barrier is reclaimed by RTEMS. .. rubric:: CONSTRAINTS: The following constraints apply to this directive: * The directive may be called from within device driver initialization context. * The directive may be called from within task context. * The directive may obtain and release the object allocator mutex. This may cause the calling task to be preempted. * The calling task does not have to be the task that created the object. Any local task that knows the object identifier can delete the object. * Where the object class corresponding to the directive is configured to use unlimited objects, the directive may free memory to the RTEMS Workspace. .. Generated from spec:/rtems/barrier/if/wait .. raw:: latex \clearpage .. index:: rtems_barrier_wait() .. index:: wait at a barrier .. _InterfaceRtemsBarrierWait: rtems_barrier_wait() -------------------- Waits at the barrier. .. rubric:: CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_barrier_wait( rtems_id id, rtems_interval timeout ); .. rubric:: PARAMETERS: ``id`` This parameter is the barrier identifier. ``timeout`` This parameter is the timeout in clock ticks. Use :c:macro:`RTEMS_NO_TIMEOUT` to wait potentially forever. .. rubric:: DESCRIPTION: This directive waits at the barrier specified by ``id``. The ``timeout`` parameter defines how long the calling task is willing to wait. Use :c:macro:`RTEMS_NO_TIMEOUT` to wait potentially forever, otherwise set a timeout interval in clock ticks. Conceptually, the calling task should always be thought of as blocking when it makes this call and being unblocked when the barrier is released. If the barrier is configured for manual release, this rule of thumb will always be valid. If the barrier is configured for automatic release, all callers will block except for the one which trips the automatic release condition. .. rubric:: RETURN VALUES: :c:macro:`RTEMS_SUCCESSFUL` The requested operation was successful. :c:macro:`RTEMS_INVALID_ID` There was no barrier associated with the identifier specified by ``id``. :c:macro:`RTEMS_TIMEOUT` The timeout happened while the calling task was waiting at the barrier. :c:macro:`RTEMS_OBJECT_WAS_DELETED` The barrier was deleted while the calling task was waiting at the barrier. .. rubric:: NOTES: For automatic release barriers, the maximum count of waiting tasks is defined during barrier creation, see :ref:`InterfaceRtemsBarrierCreate`. .. rubric:: CONSTRAINTS: The following constraints apply to this directive: * The directive may be called from within task context. * The timeout functionality of the directive requires a :term:`clock tick`. .. Generated from spec:/rtems/barrier/if/release .. raw:: latex \clearpage .. index:: rtems_barrier_release() .. index:: release a barrier .. _InterfaceRtemsBarrierRelease: rtems_barrier_release() ----------------------- Releases the barrier. .. rubric:: CALLING SEQUENCE: .. code-block:: c rtems_status_code rtems_barrier_release( rtems_id id, uint32_t *released ); .. rubric:: PARAMETERS: ``id`` This parameter is the barrier identifier. ``released`` This parameter is the pointer to an integer variable. When the directive call is successful, the number of released tasks will be stored in this variable. .. rubric:: DESCRIPTION: This directive releases the barrier specified by ``id``. All tasks waiting at the barrier will be unblocked. The number of released tasks will be returned in ``released``. .. rubric:: RETURN VALUES: :c:macro:`RTEMS_SUCCESSFUL` The requested operation was successful. :c:macro:`RTEMS_INVALID_ADDRESS` The ``released`` parameter was `NULL `_. :c:macro:`RTEMS_INVALID_ID` There was no barrier associated with the identifier specified by ``id``. .. rubric:: CONSTRAINTS: The following constraints apply to this directive: * The directive may be called from within interrupt context. * The directive may be called from within task context. * The directive may unblock a task. This may cause the calling task to be preempted.