[PATCH] Added APA terms in glossary

[Richi Dubey]

---
 c-user/glossary.rst | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/c-user/glossary.rst b/c-user/glossary.rst
index 86350a8..63a4728 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 +17,14 @@ 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 +786,20 @@ 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 search 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 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.
@@ -905,6 +928,17 @@ Glossary
         Message queues, regions, and semaphores have a wait queue associated with
         them.
 
+    Weak APA
+        Weak APA is a specialization of :term:`APA`.  
+        It 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 if a
+        processor is 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/>`_.
 
-- 
2.17.1