This makes it easier to automatically generate parts of the manager documentation in the future.
Update #3993. --- c-user/barrier/background.rst | 68 +++++++ .../directives.rst} | 169 ++---------------- c-user/barrier/index.rst | 14 ++ c-user/barrier/introduction.rst | 20 +++ c-user/barrier/operations.rst | 60 +++++++ c-user/index.rst | 2 +- 6 files changed, 174 insertions(+), 159 deletions(-) create mode 100644 c-user/barrier/background.rst rename c-user/{barrier_manager.rst => barrier/directives.rst} (55%) create mode 100644 c-user/barrier/index.rst create mode 100644 c-user/barrier/introduction.rst create mode 100644 c-user/barrier/operations.rst diff --git a/c-user/barrier/background.rst b/c-user/barrier/background.rst new file mode 100644 index 0000000..7a42d97 --- /dev/null +++ b/c-user/barrier/background.rst @@ -0,0 +1,68 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2018 On-Line Applications Research Corporation (OAR) + +Background +========== + +A barrier can be viewed as a gate at which tasks wait until the gate is opened. +This has many analogies in the real world. Horses and other farm animals may +approach a closed gate and gather in front of it, waiting for someone to open +the gate so they may proceed. Similarly, ticket holders gather at the gates of +arenas before concerts or sporting events waiting for the arena personnel to +open the gates so they may enter. + +Barriers are useful during application initialization. Each application task +can perform its local initialization before waiting for the application as a +whole to be initialized. Once all tasks have completed their independent +initializations, the "application ready" barrier can be released. + +Automatic Versus Manual Barriers +-------------------------------- + +Just as with a real-world gate, barriers may be configured to be manually +opened or automatically opened. All tasks calling the ``rtems_barrier_wait`` +directive will block until a controlling task invokes +the ``rtems_barrier_release`` directive. + +Automatic barriers are created with a limit to the number of tasks which may +simultaneously block at the barrier. Once this limit is reached, all of the +tasks are released. For example, if the automatic limit is ten tasks, then the +first nine tasks calling the ``rtems_barrier_wait`` directive will block. When +the tenth task calls the ``rtems_barrier_wait`` directive, the nine blocked +tasks will be released and the tenth task returns to the caller without +blocking. + +Building a Barrier Attribute Set +-------------------------------- + +In general, an attribute set is built by a bitwise OR of the desired attribute +components. The following table lists the set of valid barrier attributes: + +``RTEMS_BARRIER_AUTOMATIC_RELEASE`` + automatically release the barrier when the configured number of tasks are + blocked + +``RTEMS_BARRIER_MANUAL_RELEASE`` + only release the barrier when the application invokes the + ``rtems_barrier_release`` directive. (default) + +.. note:: + + Barriers only support FIFO blocking order because all waiting tasks are + released as a set. Thus the released tasks will all become ready to execute + at the same time and compete for the processor based upon their priority. + +Attribute values are specifically designed to be mutually exclusive, therefore +bitwise OR and addition operations are equivalent as long as each attribute +appears exactly once in the component list. An attribute listed as a default +is not required to appear in the attribute list, although it is a good +programming practice to specify default attributes. If all defaults are +desired, the attribute ``RTEMS_DEFAULT_ATTRIBUTES`` should be specified on this +call. + +This example demonstrates the attribute_set parameter needed to create a +barrier with the automatic release policy. The ``attribute_set`` parameter +passed to the ``rtems_barrier_create`` directive will be +``RTEMS_BARRIER_AUTOMATIC_RELEASE``. In this case, the user must also specify +the ``maximum_waiters`` parameter. diff --git a/c-user/barrier_manager.rst b/c-user/barrier/directives.rst similarity index 55% rename from c-user/barrier_manager.rst rename to c-user/barrier/directives.rst index 4438f9c..9d1fdc0 100644 --- a/c-user/barrier_manager.rst +++ b/c-user/barrier/directives.rst @@ -1,153 +1,6 @@ .. SPDX-License-Identifier: CC-BY-SA-4.0 -.. Copyright (C) 1988, 2008, 2018. -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. index:: barrier - -.. _barrier_manager: - -Barrier Manager -*************** - -Introduction -============ - -The barrier manager provides a unique synchronization capability which can be -used to have a set of tasks block and be unblocked as a set. The directives -provided by the barrier manager are: - -- rtems_barrier_create_ - Create a barrier - -- rtems_barrier_ident_ - Get ID of a barrier - -- rtems_barrier_delete_ - Delete a barrier - -- rtems_barrier_wait_ - Wait at a barrier - -- rtems_barrier_release_ - Release a barrier - -Background -========== - -A barrier can be viewed as a gate at which tasks wait until the gate is opened. -This has many analogies in the real world. Horses and other farm animals may -approach a closed gate and gather in front of it, waiting for someone to open -the gate so they may proceed. Similarly, ticket holders gather at the gates of -arenas before concerts or sporting events waiting for the arena personnel to -open the gates so they may enter. - -Barriers are useful during application initialization. Each application task -can perform its local initialization before waiting for the application as a -whole to be initialized. Once all tasks have completed their independent -initializations, the "application ready" barrier can be released. - -Automatic Versus Manual Barriers --------------------------------- - -Just as with a real-world gate, barriers may be configured to be manually -opened or automatically opened. All tasks calling the ``rtems_barrier_wait`` -directive will block until a controlling task invokes -the ``rtems_barrier_release`` directive. - -Automatic barriers are created with a limit to the number of tasks which may -simultaneously block at the barrier. Once this limit is reached, all of the -tasks are released. For example, if the automatic limit is ten tasks, then the -first nine tasks calling the ``rtems_barrier_wait`` directive will block. When -the tenth task calls the ``rtems_barrier_wait`` directive, the nine blocked -tasks will be released and the tenth task returns to the caller without -blocking. - -Building a Barrier Attribute Set --------------------------------- - -In general, an attribute set is built by a bitwise OR of the desired attribute -components. The following table lists the set of valid barrier attributes: - -``RTEMS_BARRIER_AUTOMATIC_RELEASE`` - automatically release the barrier when the configured number of tasks are - blocked - -``RTEMS_BARRIER_MANUAL_RELEASE`` - only release the barrier when the application invokes the - ``rtems_barrier_release`` directive. (default) - -.. note:: - - Barriers only support FIFO blocking order because all waiting tasks are - released as a set. Thus the released tasks will all become ready to execute - at the same time and compete for the processor based upon their priority. - -Attribute values are specifically designed to be mutually exclusive, therefore -bitwise OR and addition operations are equivalent as long as each attribute -appears exactly once in the component list. An attribute listed as a default -is not required to appear in the attribute list, although it is a good -programming practice to specify default attributes. If all defaults are -desired, the attribute ``RTEMS_DEFAULT_ATTRIBUTES`` should be specified on this -call. - -This example demonstrates the attribute_set parameter needed to create a -barrier with the automatic release policy. The ``attribute_set`` parameter -passed to the ``rtems_barrier_create`` directive will be -``RTEMS_BARRIER_AUTOMATIC_RELEASE``. In this case, the user must also specify -the ``maximum_waiters`` parameter. - -Operations -========== - -Creating a Barrier ------------------- - -The ``rtems_barrier_create`` directive creates a barrier with a user-specified -name and the desired attributes. RTEMS allocates a Barrier Control Block (BCB) -from the BCB free list. This data structure is used by RTEMS to manage the -newly created barrier. Also, a unique barrier ID is generated and returned to -the calling task. - -Obtaining Barrier IDs ---------------------- - -When a barrier is created, RTEMS generates a unique barrier ID and assigns it -to the created barrier until it is deleted. The barrier ID may be obtained by -either of two methods. First, as the result of an invocation of the -``rtems_barrier_create`` directive, the barrier ID is stored in a user provided -location. Second, the barrier ID may be obtained later using the -``rtems_barrier_ident`` directive. The barrier ID is used by other barrier -manager directives to access this barrier. - -Waiting at a Barrier --------------------- - -The ``rtems_barrier_wait`` directive is used to wait at -the specified barrier. The task may wait forever for the barrier to be -released or it may specify a timeout. Specifying a timeout limits the interval -the task will wait before returning with an error status code. - -If the barrier is configured as automatic and there are already one less then -the maximum number of waiters, then the call will unblock all tasks waiting at -the barrier and the caller will return immediately. - -When the task does wait to acquire the barrier, then it is placed in the -barrier's task wait queue in FIFO order. All tasks waiting on a barrier are -returned an error code when the barrier is deleted. - -Releasing a Barrier -------------------- - -The ``rtems_barrier_release`` directive is used to release the specified -barrier. When the ``rtems_barrier_release`` is invoked, all tasks waiting at -the barrier are immediately made ready to execute and begin to compete for the -processor to execute. - -Deleting a Barrier ------------------- - -The ``rtems_barrier_delete`` directive removes a barrier from the system and -frees its control block. A barrier can be deleted by any local task that knows -the barrier's ID. As a result of this directive, 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. Any subsequent references to the -barrier's name and ID are invalid. +.. Copyright (C) 1988, 2018 On-Line Applications Research Corporation (OAR) Directives ========== @@ -160,11 +13,11 @@ sequence, related constants, usage, and status codes. \clearpage -.. _rtems_barrier_create: - .. index:: create a barrier .. index:: rtems_barrier_create +.. _rtems_barrier_create: + BARRIER_CREATE - Create a barrier --------------------------------- @@ -237,12 +90,12 @@ NOTES: \clearpage -.. _rtems_barrier_ident: - .. index:: get ID of a barrier .. index:: obtain ID of a barrier .. index:: rtems_barrier_ident +.. _rtems_barrier_ident: + BARRIER_IDENT - Get ID of a barrier ----------------------------------- @@ -279,11 +132,11 @@ NOTES: \clearpage -.. _rtems_barrier_delete: - .. index:: delete a barrier .. index:: rtems_barrier_delete +.. _rtems_barrier_delete: + BARRIER_DELETE - Delete a barrier --------------------------------- @@ -325,11 +178,11 @@ NOTES: \clearpage -.. _rtems_barrier_wait: - .. index:: wait at a barrier .. index:: rtems_barrier_wait +.. _rtems_barrier_wait: + BARRIER_WAIT - Wait at a barrier ---------------------------------- @@ -378,11 +231,11 @@ NOTES: \clearpage -.. _rtems_barrier_release: - .. index:: release a barrier .. index:: rtems_barrier_release +.. _rtems_barrier_release: + BARRIER_RELEASE - Release a barrier ----------------------------------- diff --git a/c-user/barrier/index.rst b/c-user/barrier/index.rst new file mode 100644 index 0000000..68cd472 --- /dev/null +++ b/c-user/barrier/index.rst @@ -0,0 +1,14 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de) + +.. index:: barrier + +Barrier Manager +*************** + +.. toctree:: + + introduction + background + directives diff --git a/c-user/barrier/introduction.rst b/c-user/barrier/introduction.rst new file mode 100644 index 0000000..5965eed --- /dev/null +++ b/c-user/barrier/introduction.rst @@ -0,0 +1,20 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2018 On-Line Applications Research Corporation (OAR) + +Introduction +============ + +The barrier manager provides a unique synchronization capability which can be +used to have a set of tasks block and be unblocked as a set. The directives +provided by the barrier manager are: + +- :ref:`rtems_barrier_create` + +- :ref:`rtems_barrier_ident` + +- :ref:`rtems_barrier_delete` + +- :ref:`rtems_barrier_wait` + +- :ref:`rtems_barrier_release` diff --git a/c-user/barrier/operations.rst b/c-user/barrier/operations.rst new file mode 100644 index 0000000..52fd5d4 --- /dev/null +++ b/c-user/barrier/operations.rst @@ -0,0 +1,60 @@ +.. SPDX-License-Identifier: CC-BY-SA-4.0 + +.. Copyright (C) 1988, 2018 On-Line Applications Research Corporation (OAR) + +Operations +========== + +Creating a Barrier +------------------ + +The ``rtems_barrier_create`` directive creates a barrier with a user-specified +name and the desired attributes. RTEMS allocates a Barrier Control Block (BCB) +from the BCB free list. This data structure is used by RTEMS to manage the +newly created barrier. Also, a unique barrier ID is generated and returned to +the calling task. + +Obtaining Barrier IDs +--------------------- + +When a barrier is created, RTEMS generates a unique barrier ID and assigns it +to the created barrier until it is deleted. The barrier ID may be obtained by +either of two methods. First, as the result of an invocation of the +``rtems_barrier_create`` directive, the barrier ID is stored in a user provided +location. Second, the barrier ID may be obtained later using the +``rtems_barrier_ident`` directive. The barrier ID is used by other barrier +manager directives to access this barrier. + +Waiting at a Barrier +-------------------- + +The ``rtems_barrier_wait`` directive is used to wait at +the specified barrier. The task may wait forever for the barrier to be +released or it may specify a timeout. Specifying a timeout limits the interval +the task will wait before returning with an error status code. + +If the barrier is configured as automatic and there are already one less then +the maximum number of waiters, then the call will unblock all tasks waiting at +the barrier and the caller will return immediately. + +When the task does wait to acquire the barrier, then it is placed in the +barrier's task wait queue in FIFO order. All tasks waiting on a barrier are +returned an error code when the barrier is deleted. + +Releasing a Barrier +------------------- + +The ``rtems_barrier_release`` directive is used to release the specified +barrier. When the ``rtems_barrier_release`` is invoked, all tasks waiting at +the barrier are immediately made ready to execute and begin to compete for the +processor to execute. + +Deleting a Barrier +------------------ + +The ``rtems_barrier_delete`` directive removes a barrier from the system and +frees its control block. A barrier can be deleted by any local task that knows +the barrier's ID. As a result of this directive, 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. Any subsequent references to the +barrier's name and ID are invalid. diff --git a/c-user/index.rst b/c-user/index.rst index 412fadc..00e2bc8 100644 --- a/c-user/index.rst +++ b/c-user/index.rst @@ -36,7 +36,7 @@ RTEMS Classic API Guide (|version|). timer_manager rate_monotonic_manager sem/index - barrier_manager + barrier/index message_manager event/index signal_manager -- 2.26.2 _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel