Go to most recent revision |
Blame |
Compare with Previous |
Last modification |
View Log
| RSS feed
/*
* Project: S.Ha.R.K.
*
* Coordinators:
* Giorgio Buttazzo <giorgio@sssup.it>
* Paolo Gai <pj@gandalf.sssup.it>
*
* Authors :
* Paolo Gai <pj@gandalf.sssup.it>
* Massimiliano Giorgi <massy@gandalf.sssup.it>
* Luca Abeni <luca@gandalf.sssup.it>
* Anton Cervin
*
* ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy)
*
* http://www.sssup.it
* http://retis.sssup.it
* http://shark.sssup.it
*/
/**
------------
CVS : $Id: edf.h,v 1.1 2005-02-25 10:53:41 pj Exp $
File: $File$
Revision: $Revision: 1.1 $
Last update: $Date: 2005-02-25 10:53:41 $
------------
This file contains the scheduling module EDF (Earliest Deadline First)
Title:
EDF (Earliest Deadline First)
Task Models Accepted:
HARD_TASK_MODEL - Hard Tasks (Periodic and Sporadic)
wcet field and mit field must be != 0. They are used to set the wcet
and period of the tasks.
periodicity field can be either PERIODIC or APERIODIC
drel field must be <= mit. NOTE 1: a drel of 0 is interpreted as mit.
NOTE 2: The utilization of the task is computed as wcet/drel.
offset field specifies a release offset relative to task_activate or
group_activate.
Guest Models Accepted:
JOB_TASK_MODEL - a single guest task activation
Identified by an absolute deadline and a period.
period field is ignored
Description:
This module schedules periodic and sporadic tasks based on their
absolute deadlines. The task guarantee is based on a simple
utilization approach. The utilization factor of a task is computed
as wcet/drel. (By default, drel = mit.) A periodic task must only
be activated once; subsequent activations are triggered by an
internal timer. By contrast, an sporadic task must be explicitely
activated for each instance. NO GUARANTEE is performed on guest
tasks. The guarantee must be performed by the level that inserts
guest tasks in the EDF level.
Exceptions raised:
XUNVALID_GUEST
This level doesn't support guests of this type. When a guest
operation is called, the exception is raised.
The following exceptions may be raised by the module:
XDEADLINE_MISS
If a task misses its deadline and the EDF_ENABLE_DL_EXCEPTION
flag is set, this exception is raised.
XWCET_VIOLATION
If a task executes longer than its declared wcet and the
EDF_ENABLE_WCET_EXCEPTION flag is set, this exception is raised.
XACTIVATION
If a sporadic task is activated more often than its declared mit
and the EDF_ENABLE_ACT_EXCEPTION flag is set, this exception is
raised. This exception is also raised if a periodic task is
activated while not in the SLEEP state.
Restrictions & special features:
- Relative deadlines drel <= mit may be specified.
- An offset > 0 will delay the activation of the task by the same
amount of time. To synchronize a group of tasks, assign suitable
offsets and then use the group_activate function.
- This level doesn't manage the main task.
- The level uses the priority and timespec_priority fields.
- The guest tasks don't provide the guest_endcycle function.
- At init time, the user can specify the behavior in case of
deadline and wcet overruns. The following flags are available:
(No flags enabled) - Deadline and wcet overruns are ignored.
Pending periodic jobs are queued and are
eventually scheduled with correct deadlines
according to their original arrival times.
Sporadic tasks that arrive to often are
simply dropped.
EDF_ENABLE_DL_CHECK - When a deadline overrun occurs, the
dl_miss counter of the task is increased.
Same behavior for pending jobs as above.
EDF_ENABLE_WCET_CHECK - When a wcet overrun occurs, the
wcet_miss counter of the task is increased.
Same behavior for pending jobs as above.
EDF_ENABLE_DL_EXCEPTION - When a deadline overrun occurs, an
exception is raised.
EDF_ENABLE_WCET_EXCEPTION - When a wcet overrun occurs, an
exception is raised.
EDF_ENABLE_ACT_EXCEPTION When a periodic or sporadic task is activated
too often, an exception is raised.
- The functions EDF_get_dl_miss, EDF_get_wcet_miss, EDF_get_act_miss,
and EDF_get_nact can be used to find out the number of missed
deadlines, the number of wcet overruns, the number of skipped
activations, and the number of currently queued periodic activations.
**/
/*
* Copyright (C) 2000 Paolo Gai
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#ifndef __EDF_H__
#define __EDF_H__
#include <ll/ll.h>
#include <kernel/config.h>
#include <sys/types.h>
#include <kernel/types.h>
#include "ll/sys/cdefs.h"
__BEGIN_DECLS
/* Level flags */
#define EDF_DISABLE_ALL 0
#define EDF_ENABLE_GUARANTEE 1 /* Task guarantee enabled */
#define EDF_ENABLE_WCET_CHECK 2 /* Wcet monitoring enabled */
#define EDF_ENABLE_DL_CHECK 4 /* Deadline monitoring enabled */
#define EDF_ENABLE_WCET_EXCEPTION 8 /* Wcet overrun exception enabled */
#define EDF_ENABLE_DL_EXCEPTION 16 /* Deadline overrun exception enabled */
#define EDF_ENABLE_ACT_EXCEPTION 32 /* Activation exception enabled */
#define EDF_ENABLE_ALL 63 /* All flags enabled */
/* Registration function */
LEVEL EDF_register_level(int flags);
/**** Public utility functions ****/
/* Get the bandwidth used by the level */
bandwidth_t EDF_usedbandwidth(LEVEL l);
/* Get the number of missed deadlines for a task */
int EDF_get_dl_miss(PID p);
/* Get the number of execution overruns for a task */
int EDF_get_wcet_miss(PID p);
/* Get the number of skipped activations for a task */
int EDF_get_act_miss(PID p);
/* Get the current number of queued activations for a task */
int EDF_get_nact(PID p);
__END_DECLS
#endif