[PATCH] c-user: Add task priority glossary terms

[Joel Sherrill]

Looks good.

On Wed, May 12, 2021 at 8:07 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> ---
>  c-user/glossary.rst | 41 ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/c-user/glossary.rst b/c-user/glossary.rst
> index b3527a7..5a06c10 100644
> --- a/c-user/glossary.rst
> +++ b/c-user/glossary.rst
> @@ -194,6 +194,14 @@ Glossary
>          This term is an acronym for Cathode Ray Tube.  Normally used in
> reference to
>          the man-machine interface.
>
> +    current priority
> +        The current priority of a :term:`task` is the :term:`task
> priority` with
> +        respect to the :term:`home scheduler` of the task.  It is an
> aggregation of
> +        the :term:`real priority` and temporary priority adjustments due
> to locking
> +        protocols, the rate-monotonic period objects on some schedulers
> such as EDF,
> +        and the :term:`POSIX` sporadic server.  The current priority is an
> +        :term:`eligible priority`.
> +
>      deadline
>          A fixed time limit by which a task must have completed a set of
> actions.
>          Beyond this point, the results are of reduced value and may even
> be
> @@ -246,6 +254,12 @@ Glossary
>          This term is an acronym for
>          `Executable and Linkable Format <
> https://en.wikipedia.org/wiki/Executable_and_Linkable_Format>`_.
>
> +    eligible priority
> +        An eligible priority of a :term:`task` is the :term:`task
> priority` with
> +        respect to the corresponding :term:`eligible scheduler` of the
> task.  An
> +        eligible priority is either the :term:`current priority` and a
> +        :term:`helping priority` of a task.
> +
>      eligible scheduler
>          An eligible scheduler of a :term:`task` is a :term:`scheduler`
> which can be
>          used by the task to allocate a processor for the task.
> @@ -366,6 +380,11 @@ Glossary
>          dispatch is marked as necessary, then the next thread dispatch
> will make
>          the heir task the executing task.
>
> +    helping priority
> +        A helping priority of a :term:`task` is the :term:`task priority`
> with
> +        respect to the corresponding :term:`helping scheduler` of the
> task.  A
> +        helping priority is an :term:`eligible priority`.
> +
>      helping scheduler
>          A helping scheduler of a :term:`task` is a :term:`scheduler`
> which is a
>          :term:`eligible scheduler` and which is not the :term:`home
> scheduler` of
> @@ -632,9 +651,9 @@ Glossary
>          another task.
>
>      priority
> -        A mechanism used to represent the relative importance of an
> element in a
> -        set of items.  RTEMS uses priority to determine which task should
> -        execute.
> +        The priority is a mechanism used to represent the relative
> importance of an
> +        element in a set of items.  RTEMS uses :term:`task priorities
> <task priority>` to determine
> +        which :term:`task` should execute.
>
>      priority boosting
>          A simple approach to extend the priority inheritance protocol for
> @@ -686,6 +705,14 @@ Glossary
>          decided that other tasks are currently more important.  A task
> that is
>          ready to execute and has a processor assigned is called scheduled.
>
> +    real priority
> +        Each :term:`task` has exactly one real priority.  The real
> priority is
> +        always with respect to the :term:`home scheduler` of a task.  It
> is defined
> +        during task initialization.  It may be changed by directives such
> as
> +        :c:func:`rtems_task_set_priority` and
> +        :c:func:`rtems_task_set_scheduler`.  The real priority is the
> foundation
> +        of the :term:`current priority`.
> +
>      real-time
>          A term used to describe systems which are characterized by
> requiring
>          deterministic response times to external stimuli.  The external
> stimuli
> @@ -959,6 +986,14 @@ Glossary
>          Task migration happens in case a task stops execution on one
> processor
>          and resumes execution on another processor.
>
> +    task priority
> +        A task priority of a :term:`task` determines its importance with
> respect to
> +        other tasks.  The scheduler use task priorities to determine which
> +        :term:`ready task` gets a processor allocated.  The
> +        :term:`eligible priorities <eligible priority>` of a task define
> the position of the task in a
> +        :term:`wait queue` which uses the priority discipline.  Each task
> has at
> +        least the :term:`real priority`.
> +
>      task processor affinity
>          The set of processors on which a task is allowed to execute.
>
> --
> 2.26.2
>
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