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c-user: Add APA terms to glossary

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Richi Dubey 2020-06-30 09:01:22 +02:00 committed by Sebastian Huber
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.. SPDX-License-Identifier: CC-BY-SA-4.0
.. Copyright (C) 2020 Richi Dubey (richidubey@gmail.com)
.. Copyright (C) 2017, 2019 embedded brains GmbH (http://www.embedded-brains.de)
.. Copyright (C) 1988, 1998 On-Line Applications Research Corporation (OAR)
@ -16,6 +17,14 @@ Glossary
A term used to describe an object which has been created by an
application.
APA
This term is an acronym for Arbitrary Processor Affinity. APA schedulers
allow a thread to have an arbitrary affinity to a processor set, rather than
a restricted mapping to only one processor of the set or the ability to run
on all processors of the set.
It has two variants, :term:`Weak APA` and :term:`Strong APA`.
aperiodic task
A task which must execute only at irregular intervals and has only a soft
deadline.
@ -777,6 +786,17 @@ Glossary
:term:`return value` to indicate a successful operation or error
conditions.
Strong APA
Strong APA is a specialization of :term:`APA`. Schedulers which implement
strong APA recursively searches for a processor in the :term:`thread`'s
affinity set, whenever a thread becomes ready for execution, followed by the
processors in the affinity set of threads that are assigned the processor
present in the ready thread's affinity set. This is done to find a thread to
processor mapping that does not violate the priority ordering and to provide
a thread to processor mapping with a higher total priority of the threads
allocated a processor. Similar analysis is done when a thread blocks. See
also :cite:`Cerqueira:2014:LPA`.
suspend
A term used to describe a task that is not competing for the CPU because it
has had a ``rtems_task_suspend`` directive.
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Message queues, regions, and semaphores have a wait queue associated with
them.
Weak APA
Weak APA is a specialization of :term:`APA`. This refers to Linux's push
and pull implementation of APA model. When a :term:`thread` becomes ready
for execution, it is allocated a processor if there is an idle processor, or
a processor executing a lower priority thread in its affinity set. Unlike
:term:`Strong APA`, no thread is migrated from its processor to find a thread
to processor mapping. See also :cite:`Cerqueira:2014:LPA`.
YAML
This term is an acronym for `YAML Ain't Markup Language <https://yaml.org/>`_.