Changeset 69d6622 in rtems-docs


Ignore:
Timestamp:
Jan 13, 2017, 10:03:09 PM (4 years ago)
Author:
Kuan-Hsun Chen <c0066c@…>
Branches:
5, am, master
Children:
23b1c10
Parents:
fde6ac6
git-author:
Kuan-Hsun Chen <c0066c@…> (01/13/17 22:03:09)
git-committer:
Joel Sherrill <joel@…> (01/13/17 22:07:24)
Message:

Update documentation to reflect EDF scheduler overrun handling

Update #2795.

File:
1 edited

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  • c-user/rate_monotonic_manager.rst

    rfde6ac6 r69d6622  
    133133optimize that task.
    134134
    135 Rate Monotonic Manager Definitions
     135Periodicity Definitions
    136136----------------------------------
    137137.. index:: periodic task, definition
     
    171171
    172172The Rate Monotonic Scheduling Algorithm (RMS) is important to real-time systems
    173 designers because it allows one to guarantee that a set of tasks is
     173designers because it allows one to sufficiently guarantee that a set of tasks is
    174174schedulable.  A set of tasks is said to be schedulable if all of the tasks can
    175175meet their deadlines.  RMS provides a set of rules which can be used to perform
     
    180180.. sidebar:: *RMS*
    181181
    182   RMS is an optimal static priority algorithm for scheduling independent,
     182  RMS is an optimal fixed-priority algorithm for scheduling independent,
    183183  preemptible, periodic tasks on a single processor.
    184184
    185185RMS is optimal in the sense that if a set of tasks can be scheduled by any
    186 static priority algorithm, then RMS will be able to schedule that task set.
     186fixed-priority algorithm, then RMS will be able to schedule that task set.
    187187RMS bases it schedulability analysis on the processor utilization level below
    188188which all deadlines can be met.
     
    231231.. index:: RMS schedulability analysis
    232232
    233 RMS allows application designers to ensure that tasks can meet all deadlines,
     233RMS allows application designers to ensure that tasks can meet all deadlines under fixed-priority assignment,
    234234even under transient overload, without knowing exactly when any given task will
    235235execute by applying proven schedulability analysis rules.
     
    469469
    470470- If the rate monotonic period has expired before the task invokes the
    471   ``rtems_rate_monotonic_period`` directive, the period will be initiated with
    472   a length of period ticks and the calling task returns immediately with a
    473   timeout error status.
     471  ``rtems_rate_monotonic_period`` directive, the postponed job will be released
     472  until there is no more postponed jobs. The calling task returns immediately
     473  with a timeout error status. In the watchdog routine, the period will still
     474  be updated periodically and track the number of the postponed periods.
    474475
    475476Obtaining the Status of a Period
     
    561562any reason, the body of the loop takes more than 100 ticks to execute, the
    562563``rtems_rate_monotonic_period`` directive will return the ``RTEMS_TIMEOUT``
    563 status.  If the above task misses its deadline, it will delete the rate
    564 monotonic period and itself.
     564status and the postponed job will be released.  If the above task misses
     565its deadline, it will delete the rate monotonic period and itself.
    565566
    566567Task with Multiple Periods
     
    630631If, for any reason, the task misses any deadline, the
    631632``rtems_rate_monotonic_period`` directive will return the ``RTEMS_TIMEOUT``
    632 directive status.  If the above task misses its deadline, it will delete the
    633 rate monotonic periods and itself.
     633directive status and the postponed job will be released. If the above task misses
     634its deadline, it will delete the rate monotonic periods and itself.
    634635
    635636Directives
     
    841842    period.  If id was not running (either expired or never initiated), the
    842843    period is immediately initiated and the directive returns immediately.
     844       If id has expired its period, the postponed job will be released immediately
     845       and the following calls of this directive will release postponed
     846       jobs until there is no more deadline miss.
    843847
    844848    If invoked with a period of ``RTEMS_PERIOD_STATUS`` ticks, the current
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