javax.realtime

Class PriorityScheduler

java.lang.Object

javax.realtime.Scheduler

javax.realtime.PriorityScheduler

Direct Known Subclasses:

FirstInFirstOutScheduler

public abstract class PriorityScheduler
extends Scheduler

Class which represents the required (by the RTSJ) priority-based schedulers. The default instance is the base scheduler which uses a fixed priority, first-in-first-out, preemptive scheduling algorithm.

This scheduler, like all schedulers, governs the default values for scheduling-related parameters in its client schedulables. The defaults are as follows:

PriorityScheduler Default PriorityParameter Values

Attribute	Default Value
Priority	norm priority

Note that the system contains by default one instance of PriorityScheduler, which is the system's base scheduler and is returned by FirstInFirstOutScheduler.instance(), so a subclass of PriorityScheduler. It may, however, contain other instances of subclasses of PriorityScheduler created through this class' protected constructor. The instance returned by the FirstInFirstOutScheduler.instance() method, the base scheduler, is also returned by Scheduler.getDefaultScheduler() unless the default scheduler is changed with Scheduler.setDefaultScheduler(Scheduler).

Since:

RTSJ 2.0 PriorityScheduler is abstract.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	PriorityScheduler() Constructs an instance of PriorityScheduler.

Method Summary

Modifier and Type	Method and Description
protected boolean	addToFeasibility(Schedulable schedulable) Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate
protected SchedulingParameters	createDefaultSchedulingParameters() Create a default SchedulingParameters instance for this schedulers.
void	fireSchedulable(Schedulable schedulable) Deprecated. RTSJ 2.0
abstract int	getMaxPriority() Gets the maximum priority available for a schedulable managed by this scheduler.
static int	getMaxPriority(java.lang.Thread thread) Deprecated. since RTSJ 2.0
abstract int	getMinPriority() Gets the minimum priority available for a schedulable managed by this scheduler.
static int	getMinPriority(java.lang.Thread thread) Deprecated. since RTSJ 2.0
abstract int	getNormPriority() Gets the normal priority available for a schedulable managed by this scheduler.
static int	getNormPriority(java.lang.Thread thread) Deprecated. since RTSJ 2.0
java.lang.String	getPolicyName() Gets the policy name of this.
static PriorityScheduler	instance() Deprecated. since RTSJ 2.0
boolean	isFeasible() Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate
protected boolean	removeFromFeasibility(Schedulable schedulable) Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate
boolean	setIfFeasible(Schedulable schedulable, ReleaseParameters<?> release, MemoryParameters memory) Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate
boolean	setIfFeasible(Schedulable schedulable, ReleaseParameters<?> release, MemoryParameters memory, ProcessingGroupParameters group) Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate
boolean	setIfFeasible(Schedulable schedulable, SchedulingParameters scheduling, ReleaseParameters<?> release, MemoryParameters memory, ProcessingGroupParameters group) Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

Methods inherited from class javax.realtime.Scheduler

currentSchedulable, getDefaultScheduler, inSchedulableExecutionContext, reschedule, setDefaultScheduler

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PriorityScheduler

protected PriorityScheduler()

Constructs an instance of PriorityScheduler. Applications will likely not need any instance other than the default instance.

Method Detail

getPolicyName

public java.lang.String getPolicyName()

Gets the policy name of this.

Specified by:

getPolicyName in class Scheduler

Returns:

the policy name (Fixed Priority) as a string.

getMaxPriority

public abstract int getMaxPriority()

Gets the maximum priority available for a schedulable managed by this scheduler.

Returns:

the value of the maximum priority.

getMinPriority

public abstract int getMinPriority()

Gets the minimum priority available for a schedulable managed by this scheduler.

Returns:

the minimum priority used by this scheduler.

getNormPriority

public abstract int getNormPriority()

Gets the normal priority available for a schedulable managed by this scheduler.

Returns:

the value of the normal priority.

createDefaultSchedulingParameters

protected SchedulingParameters createDefaultSchedulingParameters()

Description copied from class: Scheduler

Create a default SchedulingParameters instance for this schedulers. A scheduler must define this in order to support setting Schedulable.setSchedulingParameters(javax.realtime.SchedulingParameters) with null as its parameter. Otherwise, null is not allowed.

Overrides:

createDefaultSchedulingParameters in class Scheduler

Returns:

parameters that are suitable for this scheduler in the current context.

getMaxPriority

@Deprecated
public static int getMaxPriority(java.lang.Thread thread)

Deprecated. since RTSJ 2.0

Gets the maximum priority for the given thread. When the given thread is a realtime thread that is scheduled by an instance of PriorityScheduler, then the maximum priority for that scheduler is returned. When the given thread is not an instance of Schedulable, the maximum priority of its thread group is returned. Otherwise an exception is thrown.

Parameters:

thread - An instance of Thread. When null, the maximum priority of this scheduler is returned.

Returns:

the maximum priority for thread

Throws:

StaticIllegalArgumentException - when thread is a realtime thread that is not scheduled by an instance of PriorityScheduler.

getMinPriority

@Deprecated
public static int getMinPriority(java.lang.Thread thread)

Deprecated. since RTSJ 2.0

Gets the minimum priority for the given thread. When the given thread is a realtime thread that is scheduled by an instance of PriorityScheduler, then the minimum priority for that scheduler is returned. When the given thread is not an instance of Schedulable, Thread.MIN_PRIORITY is returned. Otherwise an exception is thrown.

Parameters:

thread - An instance of Thread. When null, the minimum priority of this scheduler is returned.

Returns:

the minimum priority for thread

Throws:

StaticIllegalArgumentException - when thread is a realtime thread that is not scheduled by an instance of PriorityScheduler.

getNormPriority

@Deprecated
public static int getNormPriority(java.lang.Thread thread)

Deprecated. since RTSJ 2.0

Gets the "norm" priority for the given thread. When the given thread is a realtime thread that is scheduled by an instance of PriorityScheduler, then the norm priority for that scheduler is returned. When the given thread is not an instance of Schedulable, Thread.NORM_PRIORITY is returned. Otherwise an exception is thrown.

Parameters:

thread - An instance of Thread. When null, the norm priority for this scheduler is returned.

Returns:

The norm priority for thread

Throws:

StaticIllegalArgumentException - when thread is a realtime thread that is not scheduled by an instance3 of PriorityScheduler.

instance

@Deprecated
public static PriorityScheduler instance()

Deprecated. since RTSJ 2.0

Obtains a reference to the distinguished instance of PriorityScheduler, which is the system's base scheduler.

Returns:

A reference to the distinguished instance PriorityScheduler.

isFeasible

@Deprecated
public boolean isFeasible()

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

Queries this Scheduler about the feasibility of the set of schedulables currently in the feasibility set.

Implementation Notes

The default feasibility test for the PriorityScheduler considers a set of schedulables with bounded resource requirements, to always be feasible. This covers all schedulable objects with release parameters of types PeriodicParameters and SporadicParameters.

When any schedulable within the feasibility set has release parameters of the exact type AperiodicParameters (not a subclass thereof), then the feasibility set is not feasible, as aperiodic release characteristics require unbounded resources. In that case, this method will return false and all methods in the setIfFeasible family of methods will also return false. Consequently, any call to a setIfFeasible method that passes a schedulable which has release parameters of type AperiodicParameters, or passes proposed release parameters of type AperiodicParameters, will return false. The only time a setIfFeasible method can return true, when there exists in the feasibility set a schedulable with release parameters of type AperiodicParameters, is when the method will change those release parameters to not be AperiodicParameters.

Implementations may provide a feasibility test other than the default test just described. In which case the details of that test should be documented here in place of this description of the default implementation.

Specified by:

isFeasible in class Scheduler

Returns:

true, when the system is feasible; false, when not.

setIfFeasible

@Deprecated
public boolean setIfFeasible(Schedulable schedulable,
                                         ReleaseParameters<?> release,
                                         MemoryParameters memory)

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

This method first performs a feasibility analysis using the proposed parameter objects as replacements for the current parameters of Schedulable. When the resulting system is feasible, this method replaces the current parameters of Schedulable with the proposed ones.

This method does not require that the schedulable be in the feasibility set before it is called. When it is not initially a member of the feasibility set it will be added when the resulting system is feasible.

Specified by:

setIfFeasible in class Scheduler

Parameters:

schedulable - The schedulable for which the changes are proposed.

release - The proposed release parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

memory - The proposed memory parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

Returns:

true, when the resulting system is feasible and the changes are made. False, when the resulting system is not feasible and no changes are made.

Throws:

StaticIllegalArgumentException - when Schedulable is null, or Schedulable is not associated with this scheduler, or the proposed parameters are not compatible with this scheduler.

IllegalAssignmentError - when Schedulable cannot hold references to the proposed parameter objects, or the parameter objects cannot hold a reference to Schedulable.

java.lang.IllegalThreadStateException - when the new release parameters change Schedulable from periodic scheduling to some other protocol and Schedulable is currently waiting for the next release in RealtimeThread.waitForNextPeriod() or RealtimeThread.waitForNextPeriodInterruptible().

setIfFeasible

@Deprecated
public boolean setIfFeasible(Schedulable schedulable,
                                         ReleaseParameters<?> release,
                                         MemoryParameters memory,
                                         ProcessingGroupParameters group)

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

This method first performs a feasibility analysis using the proposed parameter objects as replacements for the current parameters of Schedulable. When the resulting system is feasible, this method replaces the current parameters of Schedulable with the proposed ones.

This method does not require that the schedulable be in the feasibility set before it is called. When it is not initially a member of the feasibility set it will be added when the resulting system is feasible.

Specified by:

setIfFeasible in class Scheduler

Parameters:

schedulable - The schedulable for which the changes are proposed.

release - The proposed release parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

memory - The proposed memory parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

group - The proposed processing group parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

Returns:

true, when the resulting system is feasible and the changes are made. False, when the resulting system is not feasible and no changes are made.

Throws:

StaticIllegalArgumentException - when Schedulable is null, or Schedulable is not associated with this scheduler, or the proposed parameters are not compatible with this scheduler.

IllegalAssignmentError - when Schedulable cannot hold references to the proposed parameter objects, or the parameter objects cannot hold a reference to Schedulable.

java.lang.IllegalThreadStateException - when the new release parameters change Schedulable from periodic scheduling to some other protocol and Schedulable is currently waiting for the next release in RealtimeThread.waitForNextPeriod() or RealtimeThread.waitForNextPeriodInterruptible().

setIfFeasible

@Deprecated
public boolean setIfFeasible(Schedulable schedulable,
                                         SchedulingParameters scheduling,
                                         ReleaseParameters<?> release,
                                         MemoryParameters memory,
                                         ProcessingGroupParameters group)

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

This method first performs a feasibility analysis using the proposed parameter objects as replacements for the current parameters of Schedulable. When the resulting system is feasible, this method replaces the current parameters of Schedulable with the proposed ones.

This method does not require that the schedulable be in the feasibility set before it is called. When it is not initially a member of the feasibility set it will be added when the resulting system is feasible.

Specified by:

setIfFeasible in class Scheduler

Parameters:

schedulable - The schedulable for which the changes are proposed.

scheduling - The proposed scheduling parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

release - The proposed release parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

memory - The proposed memory parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

group - The proposed processing group parameters. When null, the default value of this scheduler is used (a new object is created when the default value is not null). (See PriorityScheduler.)

Returns:

true, when the resulting system is feasible and the changes are made. False, when the resulting system is not feasible and no changes are made.

Throws:

StaticIllegalArgumentException - when Schedulable is null, or Schedulable is not associated with this scheduler, or the proposed parameters are not compatible with this scheduler.

IllegalAssignmentError - when Schedulable cannot hold references to the proposed parameter objects, or the parameter objects cannot hold a reference to Schedulable.

java.lang.IllegalThreadStateException - when the new release parameters change Schedulable from periodic scheduling to some other protocol and Schedulable is currently waiting for the next release in RealtimeThread.waitForNextPeriod() or RealtimeThread.waitForNextPeriodInterruptible().

addToFeasibility

@Deprecated
protected boolean addToFeasibility(Schedulable schedulable)

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

Informs this scheduler and cooperating facilities that the resource demands of the given instance of Schedulable will be considered in the feasibility analysis of the associated Scheduler until further notice. Whether the resulting system is feasible or not, the addition is completed.

When the object is already included in the feasibility set, does nothing.

Specified by:

addToFeasibility in class Scheduler

Parameters:

schedulable - A reference to the given instance of Schedulable

Returns:

true, when the system is feasible after the addition, otherwise False.

Throws:

StaticIllegalArgumentException - when schedulable is null, or when schedulable is not associated with this; that is schedulable.getScheduler() != this.

removeFromFeasibility

@Deprecated
protected boolean removeFromFeasibility(Schedulable schedulable)

Deprecated. as of RTSJ 2.0 The framework for feasibility analysis is inadequate

Informs this scheduler and cooperating facilities that the resource demands of the given instance of Schedulable should no longer be considered in the feasibility analysis of the associated Scheduler. Whether the resulting system is feasible or not, the removal is completed.

Specified by:

removeFromFeasibility in class Scheduler

Parameters:

schedulable - A reference to the given instance of Schedulable

Returns:

true, when the removal was successful. false, when the schedulable cannot be removed from the scheduler's feasibility set; e.g., the schedulable is not part of the scheduler's feasibility set.

Throws:

StaticIllegalArgumentException - when schedulable is null.

fireSchedulable

@Deprecated
public void fireSchedulable(Schedulable schedulable)

Deprecated. RTSJ 2.0

Triggers the execution of a schedulable (like an AsyncEventHandler).

Specified by:

fireSchedulable in class Scheduler

Parameters:

schedulable - The schedulable to make active. When null, nothing happens.

Throws:

StaticUnsupportedOperationException - Thrown in all cases by instance of PriorityScheduler.