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diff --git a/c-user/barrier/directives.rst b/c-user/barrier/directives.rst new file mode 100644 index 0000000..4eded62 --- /dev/null +++ b/c-user/barrier/directives.rst @@ -0,0 +1,415 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 2020, 2021 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 + +.. _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 :ref:`InterfaceRtemsId` object. When + the directive call is successful, the identifier of the created barrier + will be stored in this object. + +.. 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 + <https://en.cppreference.com/w/c/types/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 :ref:`InterfaceRtemsId` object. When + the directive call is successful, the object identifier of an object with + the specified name will be stored in this object. + +.. 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 + <https://en.cppreference.com/w/c/types/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 `uint32_t + <https://en.cppreference.com/w/c/types/integer>`_ object. When the + directive call is successful, the number of released tasks will be stored + in this object. + +.. 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 + <https://en.cppreference.com/w/c/types/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. |