[PATCH] Adding APA terms to glossary

[Richi Dubey]

---
 c-user/glossary.rst | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/c-user/glossary.rst b/c-user/glossary.rst
index 86350a8..691ba52 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.
+        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 +785,19 @@ Glossary
         :term:`return value` to indicate a successful operation or error
         conditions.
 
+    Strong APA
+        Strong APA is a specialization of :term:`APA`. 
+        Whenever a :term:`thread` becomes ready for execution, schedulers which 
+        implement strong APA recursively search for a processor in the thread's 
+        affinity set, 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 schedule with a higher total priority of 
+        the threads scheduled. 
+        Similar analysis is done when a thread finishes its execution.
+        
+        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 +926,16 @@ 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 push and 
+        pull implementation of APA model. On the arrival of a thread, the thread is 
+        scheduled when a processor in its affinity set is idle or a processor in its 
+        affinity set is executing a thread which is at a lower priority. 
+        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