[PATCH] APA definitions

[Richi Dubey]

---
 c-user/glossary.rst | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/c-user/glossary.rst b/c-user/glossary.rst
index 86350a8..1d95f26 100644
--- a/c-user/glossary.rst
+++ b/c-user/glossary.rst
@@ -1,5 +1,6 @@
 .. SPDX-License-Identifier: CC-BY-SA-4.0
 
+.. Copyright (C) 2020 Richi Dubey (richidubey at 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 +17,13 @@ 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.
+        In this model, a thread is allowed to have an arbitrary affinity to
+        the processor set, rather than a global mapping from one thread to all
+        processors or one thread to one processor. 
+        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 +785,19 @@ Glossary
         :term:`return value` to indicate a successful operation or error
         conditions.
 
+    Strong APA
+        Strong APA is a specialization of :term:`APA`. 
+        This variant of APA refers to a system model in which whenever a 
+        :term:`thread` becomes ready for execution, recursively the processor
+        in the thread's affinity set is checked, followed by the processor 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 provide a schedule 
+        with a higher total priority of the threads scheduled. 
+        Similar analysis is done when a thread finishes its execution.
+        
+    	: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.
@@ -905,6 +926,14 @@ Glossary
         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 pull push implementation of APA model. 
+        A ready thread is scheduled when a processor in its affinity set is idle 
+        or is executing a thread which is at a lower priority.
+        
+        :cite:`Cerqueira:2014:LPA`
+
     YAML
         This term is an acronym for `YAML Ain't Markup Language <https://yaml.org/>`_.
 
-- 
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