# [rtems-docs commit] c-user: Split up rate-monotonic manager

Sebastian Huber sebh at rtems.org
Thu Sep 3 05:00:40 UTC 2020

Module:    rtems-docs
Branch:    master
Commit:    082054b63d6365333df356a7a26381e836705354
Changeset: http://git.rtems.org/rtems-docs/commit/?id=082054b63d6365333df356a7a26381e836705354

Author:    Sebastian Huber <sebastian.huber at embedded-brains.de>
Date:      Thu Aug 20 10:03:21 2020 +0200

c-user: Split up rate-monotonic manager

This makes it easier to automatically generate parts of the manager
documentation in the future.

Update #3993.

---

c-user/index.rst                       |    2 +-
c-user/rate-monotonic/background.rst   |  390 ++++++++++++
c-user/rate-monotonic/directives.rst   |  474 ++++++++++++++
c-user/rate-monotonic/index.rst        |   16 +
c-user/rate-monotonic/introduction.rst |   33 +
c-user/rate-monotonic/operations.rst   |  200 ++++++
c-user/rate_monotonic_manager.rst      | 1091 --------------------------------
7 files changed, 1114 insertions(+), 1092 deletions(-)

diff --git a/c-user/index.rst b/c-user/index.rst
index 6de3f97..4cf9e32 100644
--- a/c-user/index.rst
+++ b/c-user/index.rst
@@ -34,7 +34,7 @@ RTEMS Classic API Guide (|version|).
interrupt/index
clock/index
timer_manager
-	rate_monotonic_manager
+	rate-monotonic/index
semaphore/index
barrier/index
message/index
diff --git a/c-user/rate-monotonic/background.rst b/c-user/rate-monotonic/background.rst
new file mode 100644
index 0000000..9ca7dff
--- /dev/null
+++ b/c-user/rate-monotonic/background.rst
@@ -0,0 +1,390 @@
+
+.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
+.. Copyright (C) 2017 Kuan-Hsun Chen.
+
+Background
+==========
+
+The rate monotonic manager provides facilities to manage the execution of
+periodic tasks.  This manager was designed to support application designers who
+utilize the Rate Monotonic Scheduling Algorithm (RMS) to ensure that their
+periodic tasks will meet their deadlines, even under transient overload
+conditions.  Although designed for hard real-time systems, the services
+provided by the rate monotonic manager may be used by any application which
+
+Rate Monotonic Manager Required Support
+---------------------------------------
+
+A clock tick is required to support the functionality provided by this manager.
+
+Period Statistics
+-----------------
+
+This manager maintains a set of statistics on each period object.  These
+statistics are reset implictly at period creation time and may be reset or
+obtained at any time by the application.  The following is a list of the
+information kept:
+
+owner
+  is the id of the thread that owns this period.
+
+count
+  is the total number of periods executed.
+
+missed_count
+  is the number of periods that were missed.
+
+min_cpu_time
+  is the minimum amount of CPU execution time consumed on any execution of the
+  periodic loop.
+
+max_cpu_time
+  is the maximum amount of CPU execution time consumed on any execution of the
+  periodic loop.
+
+total_cpu_time
+  is the total amount of CPU execution time consumed by executions of the
+  periodic loop.
+
+min_wall_time
+  is the minimum amount of wall time that passed on any execution of the
+  periodic loop.
+
+max_wall_time
+  is the maximum amount of wall time that passed on any execution of the
+  periodic loop.
+
+total_wall_time
+  is the total amount of wall time that passed during executions of the
+  periodic loop.
+
+Each period is divided into two consecutive phases.  The period starts with the
+active phase of the task and is followed by the inactive phase of the task.  In
+the inactive phase the task is blocked and waits for the start of the next
+period.  The inactive phase is skipped in case of a period miss.  The wall time
+includes the time during the active phase of the task on which the task is not
+executing on a processor.  The task is either blocked (for example it waits for
+a resource) or a higher priority tasks executes, thus preventing it from
+executing.  In case the wall time exceeds the period time, then this is a
+period miss.  The gap between the wall time and the period time is the margin
+between a period miss or success.
+
+The period statistics information is inexpensive to maintain and can provide
+very useful insights into the execution characteristics of a periodic task
+loop.  But it is just information.  The period statistics reported must be
+analyzed by the user in terms of what the applications is.  For example, in an
+application where priorities are assigned by the Rate Monotonic Algorithm, it
+would be very undesirable for high priority (i.e. frequency) tasks to miss
+their period.  Similarly, in nearly any application, if a task were supposed to
+execute its periodic loop every 10 milliseconds and it averaged 11
+milliseconds, then application requirements are not being met.
+
+The information reported can be used to determine the "hot spots" in the
+application.  Given a period's id, the user can determine the length of that
+period.  From that information and the CPU usage, the user can calculate the
+percentage of CPU time consumed by that periodic task.  For example, a task
+executing for 20 milliseconds every 200 milliseconds is consuming 10 percent of
+the processor's execution time.  This is usually enough to make it a good
+candidate for optimization.
+
+However, execution time alone is not enough to gauge the value of optimizing a
+particular task.  It is more important to optimize a task executing 2
+millisecond every 10 milliseconds (20 percent of the CPU) than one executing 10
+milliseconds every 100 (10 percent of the CPU).  As a general rule of thumb,
+the higher frequency at which a task executes, the more important it is to
+
+.. index:: periodic task, definition
+
+Periodicity Definitions
+----------------------------------
+
+A periodic task is one which must be executed at a regular interval.  The
+interval between successive iterations of the task is referred to as its
+period.  Periodic tasks can be characterized by the length of their period and
+execution time.  The period and execution time of a task can be used to
+determine the processor utilization for that task.  Processor utilization is
+the percentage of processor time used and can be calculated on a per-task or
+system-wide basis.  Typically, the task's worst-case execution time will be
+less than its period.  For example, a periodic task's requirements may state
+that it should execute for 10 milliseconds every 100 milliseconds.  Although
+the execution time may be the average, worst, or best case, the worst-case
+execution time is more appropriate for use when analyzing system behavior under
+transient overload conditions... index:: aperiodic task, definition
+
+In contrast, an aperiodic task executes at irregular intervals and has only a
+soft deadline.  In other words, the deadlines for aperiodic tasks are not
+rigid, but adequate response times are desirable.  For example, an aperiodic
+task may process user input from a terminal.
+
+
+Finally, a sporadic task is an aperiodic task with a hard deadline and minimum
+interarrival time.  The minimum interarrival time is the minimum period of time
+which exists between successive iterations of the task.  For example, a
+sporadic task could be used to process the pressing of a fire button on a
+joystick.  The mechanical action of the fire button ensures a minimum time
+period between successive activations, but the missile must be launched by a
+
+.. index:: Rate Monotonic Scheduling Algorithm, definition
+.. index:: RMS Algorithm, definition
+
+Rate Monotonic Scheduling Algorithm
+-----------------------------------
+
+The Rate Monotonic Scheduling Algorithm (RMS) is important to real-time systems
+designers because it allows one to sufficiently guarantee that a set of tasks
+is schedulable (see :cite:Liu:1973:Scheduling, :cite:Lehoczky:1989:RM,
+:cite:Sha:1990:Ada, :cite:Burns:1991:Review).
+
+A set of tasks is said to be schedulable if all of the tasks can meet their
+deadlines.  RMS provides a set of rules which can be used to perform
+a guaranteed schedulability analysis for a task set.  This analysis determines
+whether a task set is schedulable under worst-case conditions and emphasizes
+the predictability of the system's behavior.  It has been proven that:
+
+.. sidebar:: *RMS*
+
+  RMS is an optimal fixed-priority algorithm for scheduling independent,
+  preemptible, periodic tasks on a single processor.
+
+RMS is optimal in the sense that if a set of tasks can be scheduled by any
+fixed-priority algorithm, then RMS will be able to schedule that task set.
+RMS bases it schedulability analysis on the processor utilization level below
+which all deadlines can be met.
+
+RMS calls for the static assignment of task priorities based upon their period.
+The shorter a task's period, the higher its priority.  For example, a task with
+a 1 millisecond period has higher priority than a task with a 100 millisecond
+period.  If two tasks have the same period, then RMS does not distinguish
+between the tasks.  However, RTEMS specifies that when given tasks of equal
+priority, the task which has been ready longest will execute first.  RMS's
+priority assignment scheme does not provide one with exact numeric values for
+task priorities.  For example, consider the following task set and priority
+assignments:
+
++--------------------+---------------------+---------------------+
+| Task               | Period              | Priority            |
+|                    | (in milliseconds)   |                     |
++====================+=====================+=====================+
+|         1          |         100         |         Low         |
++--------------------+---------------------+---------------------+
+|         2          |          50         |       Medium        |
++--------------------+---------------------+---------------------+
+|         3          |          50         |       Medium        |
++--------------------+---------------------+---------------------+
+|         4          |          25         |        High         |
++--------------------+---------------------+---------------------+
+
+RMS only calls for task 1 to have the lowest priority, task 4 to have the
+highest priority, and tasks 2 and 3 to have an equal priority between that of
+tasks 1 and 4.  The actual RTEMS priorities assigned to the tasks must only
+adhere to those guidelines.
+
+Many applications have tasks with both hard and soft deadlines.  The tasks with
+hard deadlines are typically referred to as the critical task set, with the
+be scheduled using RMS, with the non-critical tasks not executing under
+transient overload, by simply assigning priorities such that the lowest
+priority critical task (i.e. longest period) has a higher priority than the
+highest priority non-critical task.  Although RMS may be used to assign
+priorities to the non-critical tasks, it is not necessary.  In this instance,
+schedulability is only guaranteed for the critical task set.
+
+.. index:: RMS schedulability analysis
+
+Schedulability Analysis
+-----------------------
+
+RMS allows application designers to ensure that tasks can meet all deadlines under fixed-priority assignment,
+even under transient overload, without knowing exactly when any given task will
+execute by applying proven schedulability analysis rules.
+
+Assumptions
+^^^^^^^^^^^
+
+The schedulability analysis rules for RMS were developed based on the following
+assumptions:
+
+- The requests for all tasks for which hard deadlines exist are periodic, with
+  a constant interval between requests.
+
+- Each task must complete before the next request for it occurs.
+
+- The tasks are independent in that a task does not depend on the initiation or
+  completion of requests for other tasks.
+
+- The execution time for each task without preemption or interruption is
+  constant and does not vary.
+
+- Any non-periodic tasks in the system are special.  These tasks displace
+  periodic tasks while executing and do not have hard, critical deadlines.
+
+Once the basic schedulability analysis is understood, some of the above
+assumptions can be relaxed and the side-effects accounted for.
+
+.. index:: RMS Processor Utilization Rule
+
+Processor Utilization Rule
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The Processor Utilization Rule requires that processor utilization be
+calculated based upon the period and execution time of each task.
+The fraction of processor time spent executing task index is Time(i)
+/ Period(i).  The processor utilization can be calculated as follows
+where n is the number of tasks in the set being analyzed:
+
+.. math::
+
+    Utilization = \sum_{i=1}^{n} Time_i/Period_i
+
+To ensure schedulability even under transient overload, the processor
+utilization must adhere to the following rule:
+
+.. math::
+
+    maximumUtilization = n * (2^{\frac{1}{n}} - 1)
+
+As the number of tasks increases, the above formula approaches ln(2) for a
+worst-case utilization factor of approximately 0.693.  Many tasks sets can be
+scheduled with a greater utilization factor.  In fact, the average processor
+utilization threshold for a randomly generated task set is approximately 0.88.
+See more detail in :cite:Liu:1973:Scheduling.
+
+Processor Utilization Rule Example
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This example illustrates the application of the Processor Utilization Rule to
+an application with three critical periodic tasks.  The following table details
+the RMS priority, period, execution time, and processor utilization for each
+
++------------+----------+--------+-----------+-------------+
+| Task       | RMS      | Period | Execution | Processor   |
+|            | Priority |        | Time      | Utilization |
++============+==========+========+===========+=============+
+|     1      |   High   |  100   |    15     |    0.15     |
++------------+----------+--------+-----------+-------------+
+|     2      |  Medium  |  200   |    50     |    0.25     |
++------------+----------+--------+-----------+-------------+
+|     3      |   Low    |  300   |   100     |    0.33     |
++------------+----------+--------+-----------+-------------+
+
+The total processor utilization for this task set is 0.73 which is below the
+upper bound of 3 * (2**(1/3) - 1), or 0.779, imposed by the Processor
+Utilization Rule.  Therefore, this task set is guaranteed to be schedulable
+using RMS.
+
+.. index:: RMS First Deadline Rule
+
+^^^^^^^^^^^^^^^^^^^
+
+If a given set of tasks do exceed the processor utilization upper limit imposed
+by the Processor Utilization Rule, they can still be guaranteed to meet all
+their deadlines by application of the First Deadline Rule.  This rule can be
+stated as follows:
+
+For a given set of independent periodic tasks, if each task meets its first
+deadline when all tasks are started at the same time, then the deadlines will
+always be met for any combination of start times.
+
+A key point with this rule is that ALL periodic tasks are assumed to start at
+the exact same instant in time.  Although this assumption may seem to be
+invalid, RTEMS makes it quite easy to ensure.  By having a non-preemptible user
+initialization task, all application tasks, regardless of priority, can be
+created and started before the initialization deletes itself.  This technique
+ensures that all tasks begin to compete for execution time at the same instant
+- when the user initialization task deletes itself.
+See more detail in :cite:Lehoczky:1989:RM.
+
+First Deadline Rule Example
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The First Deadline Rule can ensure schedulability even when the Processor
+Utilization Rule fails.  The example below is a modification of the Processor
+Utilization Rule example where task execution time has been increased from 15
+to 25 units.  The following table details the RMS priority, period, execution
+time, and processor utilization for each task:
+
++------------+----------+--------+-----------+-------------+
+| Task       | RMS      | Period | Execution | Processor   |
+|            | Priority |        | Time      | Utilization |
++============+==========+========+===========+=============+
+|     1      |   High   |  100   |    25     |    0.25     |
++------------+----------+--------+-----------+-------------+
+|     2      |  Medium  |  200   |    50     |    0.25     |
++------------+----------+--------+-----------+-------------+
+|     3      |   Low    |  300   |   100     |    0.33     |
++------------+----------+--------+-----------+-------------+
+
+The total processor utilization for the modified task set is 0.83 which is
+above the upper bound of 3 * (2**(1/3) - 1), or 0.779, imposed by the Processor
+Utilization Rule.  Therefore, this task set is not guaranteed to be schedulable
+using RMS.  However, the First Deadline Rule can guarantee the schedulability
+of this task set.  This rule calls for one to examine each occurrence of
+deadline until either all tasks have met their deadline or one task failed to
+meet its first deadline.  The following table details the time of each deadline
+occurrence, the maximum number of times each task may have run, the total
+execution time, and whether all the deadlines have been met:
+
++----------+------+------+------+----------------------+---------------+
+| Time     | 1    | 2    | 3    | Execution Time       | Met?          |
++==========+======+======+======+======================+===============+
+|   100    |  1   |  1   |  1   |  25 + 50 + 100 = 175 |      NO       |
++----------+------+------+------+----------------------+---------------+
+|   200    |  2   |  1   |  1   |  50 + 50 + 100 = 200 |     YES       |
++----------+------+------+------+----------------------+---------------+
+
+The key to this analysis is to recognize when each task will execute.  For
+example at time 100, task 1 must have met its first deadline, but tasks 2 and 3
+may also have begun execution.  In this example, at time 100 tasks 1 and 2 have
+completed execution and thus have met their first deadline.  Tasks 1 and 2 have
+used (25 + 50) = 75 time units, leaving (100 - 75) = 25 time units for task 3
+to begin.  Because task 3 takes 100 ticks to execute, it will not have
+completed execution at time 100.  Thus at time 100, all of the tasks except
+task 3 have met their first deadline.
+
+At time 200, task 1 must have met its second deadline and task 2 its first
+deadline.  As a result, of the first 200 time units, task 1 uses (2 * 25) = 50
+and task 2 uses 50, leaving (200 - 100) time units for task 3.  Task 3 requires
+100 time units to execute, thus it will have completed execution at time 200.
+Thus, all of the tasks have met their first deadlines at time 200, and the task
+set is schedulable using the First Deadline Rule.
+
+Relaxation of Assumptions
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The assumptions used to develop the RMS schedulability rules are uncommon in
+most real-time systems.  For example, it was assumed that tasks have constant
+unvarying execution time.  It is possible to relax this assumption, simply by
+using the worst-case execution time of each task.
+
+Another assumption is that the tasks are independent.  This means that the
+tasks do not wait for one another or contend for resources.  This assumption
+can be relaxed by accounting for the amount of time a task spends waiting to
+acquire resources.  Similarly, each task's execution time must account for any
+I/O performed and any RTEMS directive calls.
+
+In addition, the assumptions did not account for the time spent executing
+interrupt service routines.  This can be accounted for by including all the
+processor utilization by interrupt service routines in the utilization
+calculation.  Similarly, one should also account for the impact of delays in
+accessing local memory caused by direct memory access and other processors
+accessing local dual-ported memory.
+
+The assumption that nonperiodic tasks are used only for initialization or
+failure-recovery can be relaxed by placing all periodic tasks in the critical
+task set.  This task set can be scheduled and analyzed using RMS.  All
+nonperiodic tasks are placed in the non-critical task set.  Although the
+critical task set can be guaranteed to execute even under transient overload,
+the non-critical task set is not guaranteed to execute.
+
+In conclusion, the application designer must be fully cognizant of the system
+and its run-time behavior when performing schedulability analysis for a system
+using RMS.  Every hardware and software factor which impacts the execution time
+of each task must be accounted for in the schedulability analysis.
diff --git a/c-user/rate-monotonic/directives.rst b/c-user/rate-monotonic/directives.rst
new file mode 100644
index 0000000..d100c81
--- /dev/null
+++ b/c-user/rate-monotonic/directives.rst
@@ -0,0 +1,474 @@
+
+.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
+.. Copyright (C) 2017 Kuan-Hsun Chen.
+
+Directives
+==========
+
+This section details the rate monotonic manager's directives.  A subsection is
+dedicated to each of this manager's directives and describes the calling
+sequence, related constants, usage, and status codes.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: create a period
+.. index:: rtems_rate_monotonic_create
+
+.. _rtems_rate_monotonic_create:
+
+RATE_MONOTONIC_CREATE - Create a rate monotonic period
+------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_create(
+            rtems_name  name,
+            rtems_id   *id
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - rate monotonic period created successfully
+     * - RTEMS_INVALID_NAME
+       - invalid period name
+     * - RTEMS_TOO_MANY
+       - too many periods created
+
+DESCRIPTION:
+    This directive creates a rate monotonic period.  The assigned rate
+    monotonic id is returned in id.  This id is used to access the period with
+    other rate monotonic manager directives.  For control and maintenance of
+    the rate monotonic period, RTEMS allocates a PCB from the local PCB free
+    pool and initializes it.
+
+NOTES:
+    This directive may cause the calling task to be preempted due to an
+    obtain and release of the object allocator mutex.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: get ID of a period
+.. index:: obtain ID of a period
+.. index:: rtems_rate_monotonic_ident
+
+.. _rtems_rate_monotonic_ident:
+
+RATE_MONOTONIC_IDENT - Get ID of a period
+-----------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_ident(
+            rtems_name  name,
+            rtems_id   *id
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period identified successfully
+     * - RTEMS_INVALID_NAME
+
+DESCRIPTION:
+    This directive obtains the period id associated with the period name to be
+    acquired.  If the period name is not unique, then the period id will match
+    one of the periods with that name.  However, this period id is not
+    guaranteed to correspond to the desired period.  The period id is used to
+    access this period in other rate monotonic manager directives.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: cancel a period
+.. index:: rtems_rate_monotonic_cancel
+
+.. _rtems_rate_monotonic_cancel:
+
+RATE_MONOTONIC_CANCEL - Cancel a period
+---------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_cancel(
+            rtems_id id
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period canceled successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+     * - RTEMS_NOT_OWNER_OF_RESOURCE
+       - rate monotonic period not created by calling task
+
+DESCRIPTION:
+
+    This directive cancels the rate monotonic period id.  This period will be
+    reinitiated by the next invocation of rtems_rate_monotonic_period
+    with id.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+    The rate monotonic period specified by id must have been created by the
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: rtems_rate_monotonic_delete
+.. index:: delete a period
+
+.. _rtems_rate_monotonic_delete:
+
+RATE_MONOTONIC_DELETE - Delete a rate monotonic period
+------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_delete(
+            rtems_id id
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period deleted successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+
+DESCRIPTION:
+
+    This directive deletes the rate monotonic period specified by id.  If the
+    period is running, it is automatically canceled.  The PCB for the deleted
+    period is reclaimed by RTEMS.
+
+NOTES:
+    This directive may cause the calling task to be preempted due to an
+    obtain and release of the object allocator mutex.
+
+    A rate monotonic period can be deleted by a task other than the task which
+    created the period.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: conclude current period
+.. index:: start current period
+.. index:: period initiation
+.. index:: rtems_rate_monotonic_period
+
+.. _rtems_rate_monotonic_period:
+
+RATE_MONOTONIC_PERIOD - Conclude current/Start next period
+----------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_period(
+            rtems_id       id,
+            rtems_interval length
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period initiated successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+     * - RTEMS_NOT_OWNER_OF_RESOURCE
+       - period not created by calling task
+     * - RTEMS_NOT_DEFINED
+       - period has never been initiated (only possible when period is set to PERIOD_STATUS)
+     * - RTEMS_TIMEOUT
+       - period has expired
+
+DESCRIPTION:
+    This directive initiates the rate monotonic period id with a length of
+    period ticks.  If id is running, then the calling task will block for the
+    remainder of the period before reinitiating the period with the specified
+    period.  If id was not running (either expired or never initiated), the
+    period is immediately initiated and the directive returns immediately.
+    If id has expired its period, the postponed job will be released immediately
+    and the following calls of this directive will release postponed
+    jobs until there is no more deadline miss.
+
+    If invoked with a period of RTEMS_PERIOD_STATUS ticks, the current
+    state of id will be returned.  The directive status indicates the current
+    state of the period.  This does not alter the state or period of the
+    period.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: get status of period
+.. index:: obtain status of period
+.. index:: rtems_rate_monotonic_get_status
+
+.. _rtems_rate_monotonic_get_status:
+
+RATE_MONOTONIC_GET_STATUS - Obtain status from a period
+-------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_get_status(
+            rtems_id                            id,
+            rtems_rate_monotonic_period_status *status
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period status retrieved successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+     * - RTEMS_INVALID_ADDRESS
+       - invalid address of status
+     * - RTEMS_NOT_DEFINED
+       - no status is available due to the cpu usage of the task having been
+         reset since the period initiated
+
+*DESCRIPTION:
+    This directive returns status information associated with the rate
+    monotonic period id in the following data structure:
+
+    .. index:: rtems_rate_monotonic_period_status
+
+    .. code-block:: c
+
+        typedef struct {
+            rtems_id                              owner;
+            rtems_rate_monotonic_period_states    state;
+            rtems_rate_monotonic_period_time_t    since_last_period;
+            uint32_t                              postponed_jobs_count;
+        }  rtems_rate_monotonic_period_status;
+
+    .. COMMENT: RATE_MONOTONIC_INACTIVE does not have RTEMS in front of it.
+
+    A configure time option can be used to select whether the time information
+    is given in ticks or seconds and nanoseconds.  The default is seconds and
+    nanoseconds.  If the period's state is RATE_MONOTONIC_INACTIVE, both
+    time values will be set to 0.  Otherwise, both time values will contain
+    time information since the last invocation of the
+    rtems_rate_monotonic_period directive.  More specifically, the
+    since_last_period value contains the elapsed time which has occurred since
+    the last invocation of the rtems_rate_monotonic_period directive and
+    the executed_since_last_period contains how much processor time the
+    owning task has consumed since the invocation of the
+    rtems_rate_monotonic_period directive. In addition, the
+    postponed_jobs_count value contains the count of jobs which are not
+    released yet.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: get statistics of period
+.. index:: obtain statistics of period
+.. index:: rtems_rate_monotonic_get_statistics
+
+.. _rtems_rate_monotonic_get_statistics:
+
+RATE_MONOTONIC_GET_STATISTICS - Obtain statistics from a period
+---------------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_get_statistics(
+            rtems_id                                id,
+            rtems_rate_monotonic_period_statistics *statistics
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period statistics retrieved successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+     * - RTEMS_INVALID_ADDRESS
+       - invalid address of statistics
+
+DESCRIPTION:
+    This directive returns statistics information associated with the rate
+    monotonic period id in the following data structure:
+
+    .. index:: rtems_rate_monotonic_period_statistics
+
+    .. code-block:: c
+
+        typedef struct {
+            uint32_t     count;
+            uint32_t     missed_count;
+            #ifdef RTEMS_ENABLE_NANOSECOND_CPU_USAGE_STATISTICS
+              struct timespec min_cpu_time;
+              struct timespec max_cpu_time;
+              struct timespec total_cpu_time;
+            #else
+              uint32_t  min_cpu_time;
+              uint32_t  max_cpu_time;
+              uint32_t  total_cpu_time;
+            #endif
+            #ifdef RTEMS_ENABLE_NANOSECOND_RATE_MONOTONIC_STATISTICS
+              struct timespec min_wall_time;
+              struct timespec max_wall_time;
+              struct timespec total_wall_time;
+            #else
+             uint32_t  min_wall_time;
+             uint32_t  max_wall_time;
+             uint32_t  total_wall_time;
+            #endif
+        }  rtems_rate_monotonic_period_statistics;
+
+    This directive returns the current statistics information for the period
+    instance assocaited with id.  The information returned is indicated by
+    the structure above.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: reset statistics of period
+.. index:: rtems_rate_monotonic_reset_statistics
+
+.. _rtems_rate_monotonic_reset_statistics:
+
+RATE_MONOTONIC_RESET_STATISTICS - Reset statistics for a period
+---------------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        rtems_status_code rtems_rate_monotonic_reset_statistics(
+            rtems_id  id
+        );
+
+DIRECTIVE STATUS CODES:
+    .. list-table::
+     :class: rtems-table
+
+     * - RTEMS_SUCCESSFUL
+       - period initiated successfully
+     * - RTEMS_INVALID_ID
+       - invalid rate monotonic period id
+
+DESCRIPTION:
+    This directive resets the statistics information associated with this rate
+    monotonic period instance.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: reset statistics of all periods
+.. index:: rtems_rate_monotonic_reset_all_statistics
+
+.. _rtems_rate_monotonic_reset_all_statistics:
+
+RATE_MONOTONIC_RESET_ALL_STATISTICS - Reset statistics for all periods
+----------------------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        void rtems_rate_monotonic_reset_all_statistics(void);
+
+DIRECTIVE STATUS CODES:
+    NONE
+
+DESCRIPTION:
+    This directive resets the statistics information associated with all rate
+    monotonic period instances.
+
+NOTES:
+    This directive will not cause the running task to be preempted.
+
+.. raw:: latex
+
+   \clearpage
+
+.. index:: print period statistics report
+.. index:: period statistics report
+.. index:: rtems_rate_monotonic_report_statistics
+
+.. _rtems_rate_monotonic_report_statistics:
+
+RATE_MONOTONIC_REPORT_STATISTICS - Print period statistics report
+-----------------------------------------------------------------
+
+CALLING SEQUENCE:
+    .. code-block:: c
+
+        void rtems_rate_monotonic_report_statistics(void);
+
+DIRECTIVE STATUS CODES:
+    NONE
+
+DESCRIPTION:
+    This directive prints a report on all active periods which have executed at
+    least one period. The following is an example of the output generated by
+    this directive.
+
+    .. index:: rtems_rate_monotonic_period_statistics
+
+    .. code-block:: c
+
+        ID      OWNER   PERIODS  MISSED    CPU TIME    WALL TIME
+        MIN/MAX/AVG  MIN/MAX/AVG
+        0x42010001  TA1       502     0       0/1/0.99    0/0/0.00
+        0x42010002  TA2       502     0       0/1/0.99    0/0/0.00
+        0x42010003  TA3       501     0       0/1/0.99    0/0/0.00
+        0x42010004  TA4       501     0       0/1/0.99    0/0/0.00
+        0x42010005  TA5        10     0       0/1/0.90    0/0/0.00
+
+NOTES:
+    This directive will not cause the running task to be preempted.
diff --git a/c-user/rate-monotonic/index.rst b/c-user/rate-monotonic/index.rst
new file mode 100644
index 0000000..44a5765
--- /dev/null
+++ b/c-user/rate-monotonic/index.rst
@@ -0,0 +1,16 @@
+
+.. Copyright (C) 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. index:: rate mononitonic tasks
+.. index:: periodic tasks
+
+Rate Monotonic Manager
+**********************
+
+.. toctree::
+
+    introduction
+    background
+    operations
+    directives
diff --git a/c-user/rate-monotonic/introduction.rst b/c-user/rate-monotonic/introduction.rst
new file mode 100644
index 0000000..cb09898
--- /dev/null
+++ b/c-user/rate-monotonic/introduction.rst
@@ -0,0 +1,33 @@
+
+.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
+.. Copyright (C) 2017 Kuan-Hsun Chen.
+
+Introduction
+============
+
+The rate monotonic manager provides facilities to implement tasks which execute
+in a periodic fashion.  Critically, it also gathers information about the
+execution of those periods and can provide important statistics to the user
+which can be used to analyze and tune the application.  The directives provided
+by the rate monotonic manager are:
+
+- :ref:rtems_rate_monotonic_create
+
+- :ref:rtems_rate_monotonic_ident
+
+- :ref:rtems_rate_monotonic_cancel
+
+- :ref:rtems_rate_monotonic_delete
+
+- :ref:rtems_rate_monotonic_period
+
+- :ref:rtems_rate_monotonic_get_status
+
+- :ref:rtems_rate_monotonic_get_statistics
+
+- :ref:rtems_rate_monotonic_reset_statistics
+
+- :ref:rtems_rate_monotonic_reset_all_statistics
+
+- :ref:rtems_rate_monotonic_report_statistics
diff --git a/c-user/rate-monotonic/operations.rst b/c-user/rate-monotonic/operations.rst
new file mode 100644
index 0000000..d7a91b1
--- /dev/null
+++ b/c-user/rate-monotonic/operations.rst
@@ -0,0 +1,200 @@
+
+.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
+.. Copyright (C) 2017 Kuan-Hsun Chen.
+
+Operations
+==========
+
+Creating a Rate Monotonic Period
+--------------------------------
+
+The rtems_rate_monotonic_create directive creates a rate monotonic period
+which is to be used by the calling task to delineate a period.  RTEMS allocates
+a Period Control Block (PCB) from the PCB free list.  This data structure is
+used by RTEMS to manage the newly created rate monotonic period.  RTEMS returns
+a unique period ID to the application which is used by other rate monotonic
+manager directives to access this rate monotonic period.
+
+Manipulating a Period
+---------------------
+
+The rtems_rate_monotonic_period directive is used to establish and maintain
+periodic execution utilizing a previously created rate monotonic period.  Once
+initiated by the rtems_rate_monotonic_period directive, the period is said
+to run until it either expires or is reinitiated.  The state of the rate
+monotonic period results in one of the following scenarios:
+
+- If the rate monotonic period is running, the calling task will be blocked for
+  the remainder of the outstanding period and, upon completion of that period,
+  the period will be reinitiated with the specified period.
+
+- If the rate monotonic period is not currently running and has not expired, it
+  is initiated with a length of period ticks and the calling task returns
+  immediately.
+
+- If the rate monotonic period has expired before the task invokes the
+  rtems_rate_monotonic_period directive, the postponed job will be released
+  until there is no more postponed jobs. The calling task returns immediately
+  with a timeout error status. In the watchdog routine, the period will still
+  be updated periodically and track the count of the postponed jobs :cite:Chen:2016:Overrun.
+  Please note, the count of the postponed jobs is only saturated until 0xffffffff.
+
+Obtaining the Status of a Period
+--------------------------------
+
+If the rtems_rate_monotonic_period directive is invoked with a period of
+RTEMS_PERIOD_STATUS ticks, the current state of the specified rate
+monotonic period will be returned.  The following table details the
+relationship between the period's status and the directive status code returned
+by the rtems_rate_monotonic_period directive:
+
+.. list-table::
+ :class: rtems-table
+
+ * - RTEMS_SUCCESSFUL
+   - period is running
+ * - RTEMS_TIMEOUT
+   - period has expired
+ * - RTEMS_NOT_DEFINED
+   - period has never been initiated
+
+Obtaining the status of a rate monotonic period does not alter the state or
+length of that period.
+
+Canceling a Period
+------------------
+
+The rtems_rate_monotonic_cancel directive is used to stop the period
+maintained by the specified rate monotonic period.  The period is stopped and
+the rate monotonic period can be reinitiated using the
+rtems_rate_monotonic_period directive.
+
+Deleting a Rate Monotonic Period
+--------------------------------
+
+The rtems_rate_monotonic_delete directive is used to delete a rate
+monotonic period.  If the period is running and has not expired, the period is
+automatically canceled.  The rate monotonic period's control block is returned
+to the PCB free list when it is deleted.  A rate monotonic period can be
+deleted by a task other than the task which created the period.
+
+Examples
+--------
+
+The following sections illustrate common uses of rate monotonic periods to
+
+--------------------
+
+This example consists of a single periodic task which, after initialization,
+executes every 100 clock ticks.
+
+.. code-block:: c
+    :linenos:
+
+    {
+        rtems_name        name;
+        rtems_id          period;
+        rtems_status_code status;
+        name = rtems_build_name( 'P', 'E', 'R', 'D' );
+        status = rtems_rate_monotonic_create( name, &period );
+        if ( status != RTEMS_SUCCESSFUL ) {
+            printf( "rtems_monotonic_create failed with status of %d.\n", status );
+            exit( 1 );
+        }
+        while ( 1 ) {
+            if ( rtems_rate_monotonic_period( period, 100 ) == RTEMS_TIMEOUT )
+                break;
+            /* Perform some periodic actions */
+        }
+        /* missed period so delete period and SELF */
+        status = rtems_rate_monotonic_delete( period );
+        if ( status != RTEMS_SUCCESSFUL ) {
+            printf( "rtems_rate_monotonic_delete failed with status of %d.\n", status );
+            exit( 1 );
+        }
+        status = rtems_task_delete( RTEMS_SELF );    /* should not return */
+        printf( "rtems_task_delete returned with status of %d.\n", status );
+        exit( 1 );
+    }
+
+The above task creates a rate monotonic period as part of its initialization.
+The first time the loop is executed, the rtems_rate_monotonic_period
+directive will initiate the period for 100 ticks and return immediately.
+Subsequent invocations of the rtems_rate_monotonic_period directive will
+result in the task blocking for the remainder of the 100 tick period.  If, for
+any reason, the body of the loop takes more than 100 ticks to execute, the
+rtems_rate_monotonic_period directive will return the RTEMS_TIMEOUT
+status. If the above task misses its deadline, it will delete the rate
+monotonic period and itself.
+
+Task with Multiple Periods
+--------------------------
+
+This example consists of a single periodic task which, after initialization,
+performs two sets of actions every 100 clock ticks.  The first set of actions
+is performed in the first forty clock ticks of every 100 clock ticks, while the
+second set of actions is performed between the fortieth and seventieth clock
+ticks.  The last thirty clock ticks are not used by this task.
+
+.. code-block:: c
+    :linenos:
+
+    {
+        rtems_name        name_1, name_2;
+        rtems_id          period_1, period_2;
+        name_1 = rtems_build_name( 'P', 'E', 'R', '1' );
+        name_2 = rtems_build_name( 'P', 'E', 'R', '2' );
+        (void ) rtems_rate_monotonic_create( name_1, &period_1 );
+        (void ) rtems_rate_monotonic_create( name_2, &period_2 );
+        while ( 1 ) {
+            if ( rtems_rate_monotonic_period( period_1, 100 ) == RTEMS_TIMEOUT )
+                break;
+            if ( rtems_rate_monotonic_period( period_2, 40 ) == RTEMS_TIMEOUT )
+            break;
+            /*
+             *  Perform first set of actions between clock
+             *  ticks 0 and 39 of every 100 ticks.
+             */
+            if ( rtems_rate_monotonic_period( period_2, 30 ) == RTEMS_TIMEOUT )
+                break;
+            /*
+             *  Perform second set of actions between clock 40 and 69
+             *  of every 100 ticks.  THEN ...
+             *
+             *  Check to make sure we didn't miss the period_2 period.
+             */
+            if ( rtems_rate_monotonic_period( period_2, RTEMS_PERIOD_STATUS ) == RTEMS_TIMEOUT )
+                break;
+            (void) rtems_rate_monotonic_cancel( period_2 );
+        }
+        /* missed period so delete period and SELF */
+        (void ) rtems_rate_monotonic_delete( period_1 );
+        (void ) rtems_rate_monotonic_delete( period_2 );
+        (void ) rtems_task_delete( RTEMS_SELF );
+    }
+
+The above task creates two rate monotonic periods as part of its
+initialization.  The first time the loop is executed, the
+rtems_rate_monotonic_period directive will initiate the period_1 period for
+100 ticks and return immediately.  Subsequent invocations of the
+rtems_rate_monotonic_period directive for period_1 will result in the task
+blocking for the remainder of the 100 tick period.  The period_2 period is used
+to control the execution time of the two sets of actions within each 100 tick
+period established by period_1.  The rtems_rate_monotonic_cancel( period_2
+) call is performed to ensure that the period_2 period does not expire while
+the task is blocked on the period_1 period.  If this cancel operation were not
+performed, every time the rtems_rate_monotonic_period( period_2, 40 ) call
+is executed, except for the initial one, a directive status of
+RTEMS_TIMEOUT is returned.  It is important to note that every time this
+call is made, the period_2 period will be initiated immediately and the task
+will not block.
+
+If, for any reason, the task misses any deadline, the
+rtems_rate_monotonic_period directive will return the RTEMS_TIMEOUT
+directive status. If the above task misses its deadline, it will delete the
+rate monotonic periods and itself.
diff --git a/c-user/rate_monotonic_manager.rst b/c-user/rate_monotonic_manager.rst
deleted file mode 100644
index e9241bc..0000000
--- a/c-user/rate_monotonic_manager.rst
+++ /dev/null
@@ -1,1091 +0,0 @@
-
-.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
-.. Copyright (C) 2017 Kuan-Hsun Chen.
-
-.. index:: rate mononitonic tasks
-.. index:: periodic tasks
-
-Rate Monotonic Manager
-**********************
-
-Introduction
-============
-
-The rate monotonic manager provides facilities to implement tasks which execute
-in a periodic fashion.  Critically, it also gathers information about the
-execution of those periods and can provide important statistics to the user
-which can be used to analyze and tune the application.  The directives provided
-by the rate monotonic manager are:
-
-- rtems_rate_monotonic_create_ - Create a rate monotonic period
-
-- rtems_rate_monotonic_ident_ - Get ID of a period
-
-- rtems_rate_monotonic_cancel_ - Cancel a period
-
-- rtems_rate_monotonic_delete_ - Delete a rate monotonic period
-
-- rtems_rate_monotonic_period_ - Conclude current/Start next period
-
-- rtems_rate_monotonic_get_status_ - Obtain status from a period
-
-- rtems_rate_monotonic_get_statistics_ - Obtain statistics from a period
-
-- rtems_rate_monotonic_reset_statistics_ - Reset statistics for a period
-
-- rtems_rate_monotonic_reset_all_statistics_ - Reset statistics for all periods
-
-- rtems_rate_monotonic_report_statistics_ - Print period statistics report
-
-Background
-==========
-
-The rate monotonic manager provides facilities to manage the execution of
-periodic tasks.  This manager was designed to support application designers who
-utilize the Rate Monotonic Scheduling Algorithm (RMS) to ensure that their
-periodic tasks will meet their deadlines, even under transient overload
-conditions.  Although designed for hard real-time systems, the services
-provided by the rate monotonic manager may be used by any application which
-
-Rate Monotonic Manager Required Support
----------------------------------------
-
-A clock tick is required to support the functionality provided by this manager.
-
-Period Statistics
------------------
-
-This manager maintains a set of statistics on each period object.  These
-statistics are reset implictly at period creation time and may be reset or
-obtained at any time by the application.  The following is a list of the
-information kept:
-
-owner
-  is the id of the thread that owns this period.
-
-count
-  is the total number of periods executed.
-
-missed_count
-  is the number of periods that were missed.
-
-min_cpu_time
-  is the minimum amount of CPU execution time consumed on any execution of the
-  periodic loop.
-
-max_cpu_time
-  is the maximum amount of CPU execution time consumed on any execution of the
-  periodic loop.
-
-total_cpu_time
-  is the total amount of CPU execution time consumed by executions of the
-  periodic loop.
-
-min_wall_time
-  is the minimum amount of wall time that passed on any execution of the
-  periodic loop.
-
-max_wall_time
-  is the maximum amount of wall time that passed on any execution of the
-  periodic loop.
-
-total_wall_time
-  is the total amount of wall time that passed during executions of the
-  periodic loop.
-
-Each period is divided into two consecutive phases.  The period starts with the
-active phase of the task and is followed by the inactive phase of the task.  In
-the inactive phase the task is blocked and waits for the start of the next
-period.  The inactive phase is skipped in case of a period miss.  The wall time
-includes the time during the active phase of the task on which the task is not
-executing on a processor.  The task is either blocked (for example it waits for
-a resource) or a higher priority tasks executes, thus preventing it from
-executing.  In case the wall time exceeds the period time, then this is a
-period miss.  The gap between the wall time and the period time is the margin
-between a period miss or success.
-
-The period statistics information is inexpensive to maintain and can provide
-very useful insights into the execution characteristics of a periodic task
-loop.  But it is just information.  The period statistics reported must be
-analyzed by the user in terms of what the applications is.  For example, in an
-application where priorities are assigned by the Rate Monotonic Algorithm, it
-would be very undesirable for high priority (i.e. frequency) tasks to miss
-their period.  Similarly, in nearly any application, if a task were supposed to
-execute its periodic loop every 10 milliseconds and it averaged 11
-milliseconds, then application requirements are not being met.
-
-The information reported can be used to determine the "hot spots" in the
-application.  Given a period's id, the user can determine the length of that
-period.  From that information and the CPU usage, the user can calculate the
-percentage of CPU time consumed by that periodic task.  For example, a task
-executing for 20 milliseconds every 200 milliseconds is consuming 10 percent of
-the processor's execution time.  This is usually enough to make it a good
-candidate for optimization.
-
-However, execution time alone is not enough to gauge the value of optimizing a
-particular task.  It is more important to optimize a task executing 2
-millisecond every 10 milliseconds (20 percent of the CPU) than one executing 10
-milliseconds every 100 (10 percent of the CPU).  As a general rule of thumb,
-the higher frequency at which a task executes, the more important it is to
-
-.. index:: periodic task, definition
-
-Periodicity Definitions
-----------------------------------
-
-A periodic task is one which must be executed at a regular interval.  The
-interval between successive iterations of the task is referred to as its
-period.  Periodic tasks can be characterized by the length of their period and
-execution time.  The period and execution time of a task can be used to
-determine the processor utilization for that task.  Processor utilization is
-the percentage of processor time used and can be calculated on a per-task or
-system-wide basis.  Typically, the task's worst-case execution time will be
-less than its period.  For example, a periodic task's requirements may state
-that it should execute for 10 milliseconds every 100 milliseconds.  Although
-the execution time may be the average, worst, or best case, the worst-case
-execution time is more appropriate for use when analyzing system behavior under
-transient overload conditions... index:: aperiodic task, definition
-
-In contrast, an aperiodic task executes at irregular intervals and has only a
-soft deadline.  In other words, the deadlines for aperiodic tasks are not
-rigid, but adequate response times are desirable.  For example, an aperiodic
-task may process user input from a terminal.
-
-
-Finally, a sporadic task is an aperiodic task with a hard deadline and minimum
-interarrival time.  The minimum interarrival time is the minimum period of time
-which exists between successive iterations of the task.  For example, a
-sporadic task could be used to process the pressing of a fire button on a
-joystick.  The mechanical action of the fire button ensures a minimum time
-period between successive activations, but the missile must be launched by a
-
-.. index:: Rate Monotonic Scheduling Algorithm, definition
-.. index:: RMS Algorithm, definition
-
-Rate Monotonic Scheduling Algorithm
------------------------------------
-
-The Rate Monotonic Scheduling Algorithm (RMS) is important to real-time systems
-designers because it allows one to sufficiently guarantee that a set of tasks
-is schedulable (see :cite:Liu:1973:Scheduling, :cite:Lehoczky:1989:RM,
-:cite:Sha:1990:Ada, :cite:Burns:1991:Review).
-
-A set of tasks is said to be schedulable if all of the tasks can meet their
-deadlines.  RMS provides a set of rules which can be used to perform
-a guaranteed schedulability analysis for a task set.  This analysis determines
-whether a task set is schedulable under worst-case conditions and emphasizes
-the predictability of the system's behavior.  It has been proven that:
-
-.. sidebar:: *RMS*
-
-  RMS is an optimal fixed-priority algorithm for scheduling independent,
-  preemptible, periodic tasks on a single processor.
-
-RMS is optimal in the sense that if a set of tasks can be scheduled by any
-fixed-priority algorithm, then RMS will be able to schedule that task set.
-RMS bases it schedulability analysis on the processor utilization level below
-which all deadlines can be met.
-
-RMS calls for the static assignment of task priorities based upon their period.
-The shorter a task's period, the higher its priority.  For example, a task with
-a 1 millisecond period has higher priority than a task with a 100 millisecond
-period.  If two tasks have the same period, then RMS does not distinguish
-between the tasks.  However, RTEMS specifies that when given tasks of equal
-priority, the task which has been ready longest will execute first.  RMS's
-priority assignment scheme does not provide one with exact numeric values for
-task priorities.  For example, consider the following task set and priority
-assignments:
-
-+--------------------+---------------------+---------------------+
-| Task               | Period              | Priority            |
-|                    | (in milliseconds)   |                     |
-+====================+=====================+=====================+
-|         1          |         100         |         Low         |
-+--------------------+---------------------+---------------------+
-|         2          |          50         |       Medium        |
-+--------------------+---------------------+---------------------+
-|         3          |          50         |       Medium        |
-+--------------------+---------------------+---------------------+
-|         4          |          25         |        High         |
-+--------------------+---------------------+---------------------+
-
-RMS only calls for task 1 to have the lowest priority, task 4 to have the
-highest priority, and tasks 2 and 3 to have an equal priority between that of
-tasks 1 and 4.  The actual RTEMS priorities assigned to the tasks must only
-adhere to those guidelines.
-
-Many applications have tasks with both hard and soft deadlines.  The tasks with
-hard deadlines are typically referred to as the critical task set, with the
-be scheduled using RMS, with the non-critical tasks not executing under
-transient overload, by simply assigning priorities such that the lowest
-priority critical task (i.e. longest period) has a higher priority than the
-highest priority non-critical task.  Although RMS may be used to assign
-priorities to the non-critical tasks, it is not necessary.  In this instance,
-schedulability is only guaranteed for the critical task set.
-
-.. index:: RMS schedulability analysis
-
-Schedulability Analysis
------------------------
-
-RMS allows application designers to ensure that tasks can meet all deadlines under fixed-priority assignment,
-even under transient overload, without knowing exactly when any given task will
-execute by applying proven schedulability analysis rules.
-
-Assumptions
-^^^^^^^^^^^
-
-The schedulability analysis rules for RMS were developed based on the following
-assumptions:
-
-- The requests for all tasks for which hard deadlines exist are periodic, with
-  a constant interval between requests.
-
-- Each task must complete before the next request for it occurs.
-
-- The tasks are independent in that a task does not depend on the initiation or
-  completion of requests for other tasks.
-
-- The execution time for each task without preemption or interruption is
-  constant and does not vary.
-
-- Any non-periodic tasks in the system are special.  These tasks displace
-  periodic tasks while executing and do not have hard, critical deadlines.
-
-Once the basic schedulability analysis is understood, some of the above
-assumptions can be relaxed and the side-effects accounted for.
-
-.. index:: RMS Processor Utilization Rule
-
-Processor Utilization Rule
-^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The Processor Utilization Rule requires that processor utilization be
-calculated based upon the period and execution time of each task.
-The fraction of processor time spent executing task index is Time(i)
-/ Period(i).  The processor utilization can be calculated as follows
-where n is the number of tasks in the set being analyzed:
-
-.. math::
-
-    Utilization = \sum_{i=1}^{n} Time_i/Period_i
-
-To ensure schedulability even under transient overload, the processor
-utilization must adhere to the following rule:
-
-.. math::
-
-    maximumUtilization = n * (2^{\frac{1}{n}} - 1)
-
-As the number of tasks increases, the above formula approaches ln(2) for a
-worst-case utilization factor of approximately 0.693.  Many tasks sets can be
-scheduled with a greater utilization factor.  In fact, the average processor
-utilization threshold for a randomly generated task set is approximately 0.88.
-See more detail in :cite:Liu:1973:Scheduling.
-
-Processor Utilization Rule Example
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-This example illustrates the application of the Processor Utilization Rule to
-an application with three critical periodic tasks.  The following table details
-the RMS priority, period, execution time, and processor utilization for each
-
-+------------+----------+--------+-----------+-------------+
-| Task       | RMS      | Period | Execution | Processor   |
-|            | Priority |        | Time      | Utilization |
-+============+==========+========+===========+=============+
-|     1      |   High   |  100   |    15     |    0.15     |
-+------------+----------+--------+-----------+-------------+
-|     2      |  Medium  |  200   |    50     |    0.25     |
-+------------+----------+--------+-----------+-------------+
-|     3      |   Low    |  300   |   100     |    0.33     |
-+------------+----------+--------+-----------+-------------+
-
-The total processor utilization for this task set is 0.73 which is below the
-upper bound of 3 * (2**(1/3) - 1), or 0.779, imposed by the Processor
-Utilization Rule.  Therefore, this task set is guaranteed to be schedulable
-using RMS.
-
-.. index:: RMS First Deadline Rule
-
-^^^^^^^^^^^^^^^^^^^
-
-If a given set of tasks do exceed the processor utilization upper limit imposed
-by the Processor Utilization Rule, they can still be guaranteed to meet all
-their deadlines by application of the First Deadline Rule.  This rule can be
-stated as follows:
-
-For a given set of independent periodic tasks, if each task meets its first
-deadline when all tasks are started at the same time, then the deadlines will
-always be met for any combination of start times.
-
-A key point with this rule is that ALL periodic tasks are assumed to start at
-the exact same instant in time.  Although this assumption may seem to be
-invalid, RTEMS makes it quite easy to ensure.  By having a non-preemptible user
-initialization task, all application tasks, regardless of priority, can be
-created and started before the initialization deletes itself.  This technique
-ensures that all tasks begin to compete for execution time at the same instant
-- when the user initialization task deletes itself.
-See more detail in :cite:Lehoczky:1989:RM.
-
-First Deadline Rule Example
-^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The First Deadline Rule can ensure schedulability even when the Processor
-Utilization Rule fails.  The example below is a modification of the Processor
-Utilization Rule example where task execution time has been increased from 15
-to 25 units.  The following table details the RMS priority, period, execution
-time, and processor utilization for each task:
-
-+------------+----------+--------+-----------+-------------+
-| Task       | RMS      | Period | Execution | Processor   |
-|            | Priority |        | Time      | Utilization |
-+============+==========+========+===========+=============+
-|     1      |   High   |  100   |    25     |    0.25     |
-+------------+----------+--------+-----------+-------------+
-|     2      |  Medium  |  200   |    50     |    0.25     |
-+------------+----------+--------+-----------+-------------+
-|     3      |   Low    |  300   |   100     |    0.33     |
-+------------+----------+--------+-----------+-------------+
-
-The total processor utilization for the modified task set is 0.83 which is
-above the upper bound of 3 * (2**(1/3) - 1), or 0.779, imposed by the Processor
-Utilization Rule.  Therefore, this task set is not guaranteed to be schedulable
-using RMS.  However, the First Deadline Rule can guarantee the schedulability
-of this task set.  This rule calls for one to examine each occurrence of
-deadline until either all tasks have met their deadline or one task failed to
-meet its first deadline.  The following table details the time of each deadline
-occurrence, the maximum number of times each task may have run, the total
-execution time, and whether all the deadlines have been met:
-
-+----------+------+------+------+----------------------+---------------+
-| Time     | 1    | 2    | 3    | Execution Time       | Met?          |
-+==========+======+======+======+======================+===============+
-|   100    |  1   |  1   |  1   |  25 + 50 + 100 = 175 |      NO       |
-+----------+------+------+------+----------------------+---------------+
-|   200    |  2   |  1   |  1   |  50 + 50 + 100 = 200 |     YES       |
-+----------+------+------+------+----------------------+---------------+
-
-The key to this analysis is to recognize when each task will execute.  For
-example at time 100, task 1 must have met its first deadline, but tasks 2 and 3
-may also have begun execution.  In this example, at time 100 tasks 1 and 2 have
-completed execution and thus have met their first deadline.  Tasks 1 and 2 have
-used (25 + 50) = 75 time units, leaving (100 - 75) = 25 time units for task 3
-to begin.  Because task 3 takes 100 ticks to execute, it will not have
-completed execution at time 100.  Thus at time 100, all of the tasks except
-task 3 have met their first deadline.
-
-At time 200, task 1 must have met its second deadline and task 2 its first
-deadline.  As a result, of the first 200 time units, task 1 uses (2 * 25) = 50
-and task 2 uses 50, leaving (200 - 100) time units for task 3.  Task 3 requires
-100 time units to execute, thus it will have completed execution at time 200.
-Thus, all of the tasks have met their first deadlines at time 200, and the task
-set is schedulable using the First Deadline Rule.
-
-Relaxation of Assumptions
-^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The assumptions used to develop the RMS schedulability rules are uncommon in
-most real-time systems.  For example, it was assumed that tasks have constant
-unvarying execution time.  It is possible to relax this assumption, simply by
-using the worst-case execution time of each task.
-
-Another assumption is that the tasks are independent.  This means that the
-tasks do not wait for one another or contend for resources.  This assumption
-can be relaxed by accounting for the amount of time a task spends waiting to
-acquire resources.  Similarly, each task's execution time must account for any
-I/O performed and any RTEMS directive calls.
-
-In addition, the assumptions did not account for the time spent executing
-interrupt service routines.  This can be accounted for by including all the
-processor utilization by interrupt service routines in the utilization
-calculation.  Similarly, one should also account for the impact of delays in
-accessing local memory caused by direct memory access and other processors
-accessing local dual-ported memory.
-
-The assumption that nonperiodic tasks are used only for initialization or
-failure-recovery can be relaxed by placing all periodic tasks in the critical
-task set.  This task set can be scheduled and analyzed using RMS.  All
-nonperiodic tasks are placed in the non-critical task set.  Although the
-critical task set can be guaranteed to execute even under transient overload,
-the non-critical task set is not guaranteed to execute.
-
-In conclusion, the application designer must be fully cognizant of the system
-and its run-time behavior when performing schedulability analysis for a system
-using RMS.  Every hardware and software factor which impacts the execution time
-of each task must be accounted for in the schedulability analysis.
-
-Operations
-==========
-
-Creating a Rate Monotonic Period
---------------------------------
-
-The rtems_rate_monotonic_create directive creates a rate monotonic period
-which is to be used by the calling task to delineate a period.  RTEMS allocates
-a Period Control Block (PCB) from the PCB free list.  This data structure is
-used by RTEMS to manage the newly created rate monotonic period.  RTEMS returns
-a unique period ID to the application which is used by other rate monotonic
-manager directives to access this rate monotonic period.
-
-Manipulating a Period
----------------------
-
-The rtems_rate_monotonic_period directive is used to establish and maintain
-periodic execution utilizing a previously created rate monotonic period.  Once
-initiated by the rtems_rate_monotonic_period directive, the period is said
-to run until it either expires or is reinitiated.  The state of the rate
-monotonic period results in one of the following scenarios:
-
-- If the rate monotonic period is running, the calling task will be blocked for
-  the remainder of the outstanding period and, upon completion of that period,
-  the period will be reinitiated with the specified period.
-
-- If the rate monotonic period is not currently running and has not expired, it
-  is initiated with a length of period ticks and the calling task returns
-  immediately.
-
-- If the rate monotonic period has expired before the task invokes the
-  rtems_rate_monotonic_period directive, the postponed job will be released
-  until there is no more postponed jobs. The calling task returns immediately
-  with a timeout error status. In the watchdog routine, the period will still
-  be updated periodically and track the count of the postponed jobs :cite:Chen:2016:Overrun.
-  Please note, the count of the postponed jobs is only saturated until 0xffffffff.
-
-Obtaining the Status of a Period
---------------------------------
-
-If the rtems_rate_monotonic_period directive is invoked with a period of
-RTEMS_PERIOD_STATUS ticks, the current state of the specified rate
-monotonic period will be returned.  The following table details the
-relationship between the period's status and the directive status code returned
-by the rtems_rate_monotonic_period directive:
-
-.. list-table::
- :class: rtems-table
-
- * - RTEMS_SUCCESSFUL
-   - period is running
- * - RTEMS_TIMEOUT
-   - period has expired
- * - RTEMS_NOT_DEFINED
-   - period has never been initiated
-
-Obtaining the status of a rate monotonic period does not alter the state or
-length of that period.
-
-Canceling a Period
-------------------
-
-The rtems_rate_monotonic_cancel directive is used to stop the period
-maintained by the specified rate monotonic period.  The period is stopped and
-the rate monotonic period can be reinitiated using the
-rtems_rate_monotonic_period directive.
-
-Deleting a Rate Monotonic Period
---------------------------------
-
-The rtems_rate_monotonic_delete directive is used to delete a rate
-monotonic period.  If the period is running and has not expired, the period is
-automatically canceled.  The rate monotonic period's control block is returned
-to the PCB free list when it is deleted.  A rate monotonic period can be
-deleted by a task other than the task which created the period.
-
-Examples
---------
-
-The following sections illustrate common uses of rate monotonic periods to
-
---------------------
-
-This example consists of a single periodic task which, after initialization,
-executes every 100 clock ticks.
-
-.. code-block:: c
-    :linenos:
-
-    {
-        rtems_name        name;
-        rtems_id          period;
-        rtems_status_code status;
-        name = rtems_build_name( 'P', 'E', 'R', 'D' );
-        status = rtems_rate_monotonic_create( name, &period );
-        if ( status != RTEMS_SUCCESSFUL ) {
-            printf( "rtems_monotonic_create failed with status of %d.\n", status );
-            exit( 1 );
-        }
-        while ( 1 ) {
-            if ( rtems_rate_monotonic_period( period, 100 ) == RTEMS_TIMEOUT )
-                break;
-            /* Perform some periodic actions */
-        }
-        /* missed period so delete period and SELF */
-        status = rtems_rate_monotonic_delete( period );
-        if ( status != RTEMS_SUCCESSFUL ) {
-            printf( "rtems_rate_monotonic_delete failed with status of %d.\n", status );
-            exit( 1 );
-        }
-        status = rtems_task_delete( RTEMS_SELF );    /* should not return */
-        printf( "rtems_task_delete returned with status of %d.\n", status );
-        exit( 1 );
-    }
-
-The above task creates a rate monotonic period as part of its initialization.
-The first time the loop is executed, the rtems_rate_monotonic_period
-directive will initiate the period for 100 ticks and return immediately.
-Subsequent invocations of the rtems_rate_monotonic_period directive will
-result in the task blocking for the remainder of the 100 tick period.  If, for
-any reason, the body of the loop takes more than 100 ticks to execute, the
-rtems_rate_monotonic_period directive will return the RTEMS_TIMEOUT
-status. If the above task misses its deadline, it will delete the rate
-monotonic period and itself.
-
-Task with Multiple Periods
---------------------------
-
-This example consists of a single periodic task which, after initialization,
-performs two sets of actions every 100 clock ticks.  The first set of actions
-is performed in the first forty clock ticks of every 100 clock ticks, while the
-second set of actions is performed between the fortieth and seventieth clock
-ticks.  The last thirty clock ticks are not used by this task.
-
-.. code-block:: c
-    :linenos:
-
-    {
-        rtems_name        name_1, name_2;
-        rtems_id          period_1, period_2;
-        name_1 = rtems_build_name( 'P', 'E', 'R', '1' );
-        name_2 = rtems_build_name( 'P', 'E', 'R', '2' );
-        (void ) rtems_rate_monotonic_create( name_1, &period_1 );
-        (void ) rtems_rate_monotonic_create( name_2, &period_2 );
-        while ( 1 ) {
-            if ( rtems_rate_monotonic_period( period_1, 100 ) == RTEMS_TIMEOUT )
-                break;
-            if ( rtems_rate_monotonic_period( period_2, 40 ) == RTEMS_TIMEOUT )
-            break;
-            /*
-             *  Perform first set of actions between clock
-             *  ticks 0 and 39 of every 100 ticks.
-             */
-            if ( rtems_rate_monotonic_period( period_2, 30 ) == RTEMS_TIMEOUT )
-                break;
-            /*
-             *  Perform second set of actions between clock 40 and 69
-             *  of every 100 ticks.  THEN ...
-             *
-             *  Check to make sure we didn't miss the period_2 period.
-             */
-            if ( rtems_rate_monotonic_period( period_2, RTEMS_PERIOD_STATUS ) == RTEMS_TIMEOUT )
-                break;
-            (void) rtems_rate_monotonic_cancel( period_2 );
-        }
-        /* missed period so delete period and SELF */
-        (void ) rtems_rate_monotonic_delete( period_1 );
-        (void ) rtems_rate_monotonic_delete( period_2 );
-        (void ) rtems_task_delete( RTEMS_SELF );
-    }
-
-The above task creates two rate monotonic periods as part of its
-initialization.  The first time the loop is executed, the
-rtems_rate_monotonic_period directive will initiate the period_1 period for
-100 ticks and return immediately.  Subsequent invocations of the
-rtems_rate_monotonic_period directive for period_1 will result in the task
-blocking for the remainder of the 100 tick period.  The period_2 period is used
-to control the execution time of the two sets of actions within each 100 tick
-period established by period_1.  The rtems_rate_monotonic_cancel( period_2
-) call is performed to ensure that the period_2 period does not expire while
-the task is blocked on the period_1 period.  If this cancel operation were not
-performed, every time the rtems_rate_monotonic_period( period_2, 40 ) call
-is executed, except for the initial one, a directive status of
-RTEMS_TIMEOUT is returned.  It is important to note that every time this
-call is made, the period_2 period will be initiated immediately and the task
-will not block.
-
-If, for any reason, the task misses any deadline, the
-rtems_rate_monotonic_period directive will return the RTEMS_TIMEOUT
-directive status. If the above task misses its deadline, it will delete the
-rate monotonic periods and itself.
-
-Directives
-==========
-
-This section details the rate monotonic manager's directives.  A subsection is
-dedicated to each of this manager's directives and describes the calling
-sequence, related constants, usage, and status codes.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: create a period
-.. index:: rtems_rate_monotonic_create
-
-.. _rtems_rate_monotonic_create:
-
-RATE_MONOTONIC_CREATE - Create a rate monotonic period
-------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_create(
-            rtems_name  name,
-            rtems_id   *id
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - rate monotonic period created successfully
-     * - RTEMS_INVALID_NAME
-       - invalid period name
-     * - RTEMS_TOO_MANY
-       - too many periods created
-
-DESCRIPTION:
-    This directive creates a rate monotonic period.  The assigned rate
-    monotonic id is returned in id.  This id is used to access the period with
-    other rate monotonic manager directives.  For control and maintenance of
-    the rate monotonic period, RTEMS allocates a PCB from the local PCB free
-    pool and initializes it.
-
-NOTES:
-    This directive may cause the calling task to be preempted due to an
-    obtain and release of the object allocator mutex.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: get ID of a period
-.. index:: obtain ID of a period
-.. index:: rtems_rate_monotonic_ident
-
-.. _rtems_rate_monotonic_ident:
-
-RATE_MONOTONIC_IDENT - Get ID of a period
------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_ident(
-            rtems_name  name,
-            rtems_id   *id
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period identified successfully
-     * - RTEMS_INVALID_NAME
-
-DESCRIPTION:
-    This directive obtains the period id associated with the period name to be
-    acquired.  If the period name is not unique, then the period id will match
-    one of the periods with that name.  However, this period id is not
-    guaranteed to correspond to the desired period.  The period id is used to
-    access this period in other rate monotonic manager directives.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: cancel a period
-.. index:: rtems_rate_monotonic_cancel
-
-.. _rtems_rate_monotonic_cancel:
-
-RATE_MONOTONIC_CANCEL - Cancel a period
----------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_cancel(
-            rtems_id id
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period canceled successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-     * - RTEMS_NOT_OWNER_OF_RESOURCE
-       - rate monotonic period not created by calling task
-
-DESCRIPTION:
-
-    This directive cancels the rate monotonic period id.  This period will be
-    reinitiated by the next invocation of rtems_rate_monotonic_period
-    with id.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-    The rate monotonic period specified by id must have been created by the
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: rtems_rate_monotonic_delete
-.. index:: delete a period
-
-.. _rtems_rate_monotonic_delete:
-
-RATE_MONOTONIC_DELETE - Delete a rate monotonic period
-------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_delete(
-            rtems_id id
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period deleted successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-
-DESCRIPTION:
-
-    This directive deletes the rate monotonic period specified by id.  If the
-    period is running, it is automatically canceled.  The PCB for the deleted
-    period is reclaimed by RTEMS.
-
-NOTES:
-    This directive may cause the calling task to be preempted due to an
-    obtain and release of the object allocator mutex.
-
-    A rate monotonic period can be deleted by a task other than the task which
-    created the period.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: conclude current period
-.. index:: start current period
-.. index:: period initiation
-.. index:: rtems_rate_monotonic_period
-
-.. _rtems_rate_monotonic_period:
-
-RATE_MONOTONIC_PERIOD - Conclude current/Start next period
-----------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_period(
-            rtems_id       id,
-            rtems_interval length
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period initiated successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-     * - RTEMS_NOT_OWNER_OF_RESOURCE
-       - period not created by calling task
-     * - RTEMS_NOT_DEFINED
-       - period has never been initiated (only possible when period is set to PERIOD_STATUS)
-     * - RTEMS_TIMEOUT
-       - period has expired
-
-DESCRIPTION:
-    This directive initiates the rate monotonic period id with a length of
-    period ticks.  If id is running, then the calling task will block for the
-    remainder of the period before reinitiating the period with the specified
-    period.  If id was not running (either expired or never initiated), the
-    period is immediately initiated and the directive returns immediately.
-    If id has expired its period, the postponed job will be released immediately
-    and the following calls of this directive will release postponed
-    jobs until there is no more deadline miss.
-
-    If invoked with a period of RTEMS_PERIOD_STATUS ticks, the current
-    state of id will be returned.  The directive status indicates the current
-    state of the period.  This does not alter the state or period of the
-    period.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: get status of period
-.. index:: obtain status of period
-.. index:: rtems_rate_monotonic_get_status
-
-.. _rtems_rate_monotonic_get_status:
-
-RATE_MONOTONIC_GET_STATUS - Obtain status from a period
--------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_get_status(
-            rtems_id                            id,
-            rtems_rate_monotonic_period_status *status
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period status retrieved successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-     * - RTEMS_INVALID_ADDRESS
-       - invalid address of status
-     * - RTEMS_NOT_DEFINED
-       - no status is available due to the cpu usage of the task having been
-         reset since the period initiated
-
-*DESCRIPTION:
-    This directive returns status information associated with the rate
-    monotonic period id in the following data structure:
-
-    .. index:: rtems_rate_monotonic_period_status
-
-    .. code-block:: c
-
-        typedef struct {
-            rtems_id                              owner;
-            rtems_rate_monotonic_period_states    state;
-            rtems_rate_monotonic_period_time_t    since_last_period;
-            uint32_t                              postponed_jobs_count;
-        }  rtems_rate_monotonic_period_status;
-
-    .. COMMENT: RATE_MONOTONIC_INACTIVE does not have RTEMS in front of it.
-
-    A configure time option can be used to select whether the time information
-    is given in ticks or seconds and nanoseconds.  The default is seconds and
-    nanoseconds.  If the period's state is RATE_MONOTONIC_INACTIVE, both
-    time values will be set to 0.  Otherwise, both time values will contain
-    time information since the last invocation of the
-    rtems_rate_monotonic_period directive.  More specifically, the
-    since_last_period value contains the elapsed time which has occurred since
-    the last invocation of the rtems_rate_monotonic_period directive and
-    the executed_since_last_period contains how much processor time the
-    owning task has consumed since the invocation of the
-    rtems_rate_monotonic_period directive. In addition, the
-    postponed_jobs_count value contains the count of jobs which are not
-    released yet.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: get statistics of period
-.. index:: obtain statistics of period
-.. index:: rtems_rate_monotonic_get_statistics
-
-.. _rtems_rate_monotonic_get_statistics:
-
-RATE_MONOTONIC_GET_STATISTICS - Obtain statistics from a period
----------------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_get_statistics(
-            rtems_id                                id,
-            rtems_rate_monotonic_period_statistics *statistics
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period statistics retrieved successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-     * - RTEMS_INVALID_ADDRESS
-       - invalid address of statistics
-
-DESCRIPTION:
-    This directive returns statistics information associated with the rate
-    monotonic period id in the following data structure:
-
-    .. index:: rtems_rate_monotonic_period_statistics
-
-    .. code-block:: c
-
-        typedef struct {
-            uint32_t     count;
-            uint32_t     missed_count;
-            #ifdef RTEMS_ENABLE_NANOSECOND_CPU_USAGE_STATISTICS
-              struct timespec min_cpu_time;
-              struct timespec max_cpu_time;
-              struct timespec total_cpu_time;
-            #else
-              uint32_t  min_cpu_time;
-              uint32_t  max_cpu_time;
-              uint32_t  total_cpu_time;
-            #endif
-            #ifdef RTEMS_ENABLE_NANOSECOND_RATE_MONOTONIC_STATISTICS
-              struct timespec min_wall_time;
-              struct timespec max_wall_time;
-              struct timespec total_wall_time;
-            #else
-             uint32_t  min_wall_time;
-             uint32_t  max_wall_time;
-             uint32_t  total_wall_time;
-            #endif
-        }  rtems_rate_monotonic_period_statistics;
-
-    This directive returns the current statistics information for the period
-    instance assocaited with id.  The information returned is indicated by
-    the structure above.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: reset statistics of period
-.. index:: rtems_rate_monotonic_reset_statistics
-
-.. _rtems_rate_monotonic_reset_statistics:
-
-RATE_MONOTONIC_RESET_STATISTICS - Reset statistics for a period
----------------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        rtems_status_code rtems_rate_monotonic_reset_statistics(
-            rtems_id  id
-        );
-
-DIRECTIVE STATUS CODES:
-    .. list-table::
-     :class: rtems-table
-
-     * - RTEMS_SUCCESSFUL
-       - period initiated successfully
-     * - RTEMS_INVALID_ID
-       - invalid rate monotonic period id
-
-DESCRIPTION:
-    This directive resets the statistics information associated with this rate
-    monotonic period instance.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: reset statistics of all periods
-.. index:: rtems_rate_monotonic_reset_all_statistics
-
-.. _rtems_rate_monotonic_reset_all_statistics:
-
-RATE_MONOTONIC_RESET_ALL_STATISTICS - Reset statistics for all periods
-----------------------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        void rtems_rate_monotonic_reset_all_statistics(void);
-
-DIRECTIVE STATUS CODES:
-    NONE
-
-DESCRIPTION:
-    This directive resets the statistics information associated with all rate
-    monotonic period instances.
-
-NOTES:
-    This directive will not cause the running task to be preempted.
-
-.. raw:: latex
-
-   \clearpage
-
-.. index:: print period statistics report
-.. index:: period statistics report
-.. index:: rtems_rate_monotonic_report_statistics
-
-.. _rtems_rate_monotonic_report_statistics:
-
-RATE_MONOTONIC_REPORT_STATISTICS - Print period statistics report
------------------------------------------------------------------
-
-CALLING SEQUENCE:
-    .. code-block:: c
-
-        void rtems_rate_monotonic_report_statistics(void);
-
-DIRECTIVE STATUS CODES:
-    NONE
-
-DESCRIPTION:
-    This directive prints a report on all active periods which have executed at
-    least one period. The following is an example of the output generated by
-    this directive.
-
-    .. index:: rtems_rate_monotonic_period_statistics
-
-    .. code-block:: c
-
-        ID      OWNER   PERIODS  MISSED    CPU TIME    WALL TIME
-        MIN/MAX/AVG  MIN/MAX/AVG
-        0x42010001  TA1       502     0       0/1/0.99    0/0/0.00
-        0x42010002  TA2       502     0       0/1/0.99    0/0/0.00
-        0x42010003  TA3       501     0       0/1/0.99    0/0/0.00
-        0x42010004  TA4       501     0       0/1/0.99    0/0/0.00
-        0x42010005  TA5        10     0       0/1/0.90    0/0/0.00
-
-NOTES:
-    This directive will not cause the running task to be preempted.