javax.realtime

Class Scheduler

java.lang.Object

javax.realtime.Scheduler

Direct Known Subclasses:

PriorityScheduler

public abstract class Scheduler
extends Object

Jamaica Real-Time Specification for Java class Scheduler.

Instances of concrete subclasses of this class manage the execution of schedulable objects according to a given scheduling policy.

Additionally, subclasses may implement an algorithm to perform feasibility analysis on the set of schedulable objects is feasible under the implemented scheduling policy.

Concrete subclasses should typically be singletons, i.e., they should provide a method instance() to obtain the instance of the scheduler.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Scheduler() Constructor to be called by sub-classes of this to initialize the Scheduler.

Method Summary

Modifier and Type	Method and Description
protected abstract boolean	addToFeasibility(Schedulable schedulable) Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.
protected SchedulingParameters	createDefaultSchedulingParameters() Create a default SchedulingParameters instance for this scheduler.
static Schedulable	currentSchedulable() Gets the current execution context when called from a Schedulable execution context.
abstract void	fireSchedulable(Schedulable schedulable) Deprecated. since RTSJ 2.0
static Scheduler	getDefaultScheduler() getDefaultScheduler returns a reference to the default scheduler, which is an instance of PriorityScheduler.
abstract String	getPolicyName() getPolicyName returns the name of this scheduling policy.
static boolean	inSchedulableExecutionContext() Determines whether the current calling context is a Schedulable: RealtimeThread or AsyncBaseEventHandler.
abstract boolean	isFeasible() Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.
protected abstract boolean	removeFromFeasibility(Schedulable schedulable) Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.
abstract void	reschedule(Thread thread, SchedulingParameters eligibility) Promotes a java.lang.Thread to realtime priority under this scheduler.
static void	setDefaultScheduler(Scheduler scheduler) setDefaultScheduler sets the default scheduler to the given scheduler.
abstract boolean	setIfFeasible(Schedulable schedulable, ReleaseParameters<?> release, MemoryParameters memory) Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.
abstract boolean	setIfFeasible(Schedulable schedulable, ReleaseParameters<?> release, MemoryParameters memory, ProcessingGroupParameters group) Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.
abstract boolean	setIfFeasible(Schedulable schedulable, SchedulingParameters scheduling, ReleaseParameters<?> release, MemoryParameters memory, ProcessingGroupParameters group) Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

Methods inherited from class java.lang.Object

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

Constructor Detail

Scheduler

protected Scheduler()

Constructor to be called by sub-classes of this to initialize the Scheduler.

Method Detail

reschedule

public abstract void reschedule(Thread thread,
                                SchedulingParameters eligibility)

Promotes a java.lang.Thread to realtime priority under this scheduler. The affected thread will be scheduled as if it was a RealtimeThread with the given eligibility. This does not make the affected thread a RealtimeThread, however, and it will not have access to facilities reserved for instances of RealtimeThread. Instances of RealtimeThread will be treated as if their scheduling parameters were set to eligibility.

Throws:

StaticIllegalArgumentException - when eligibility is not valid for the scheduler.

StaticIllegalStateException - when eligibility specifies parameters that are out of range for the scheduler or the threads state or the intersection of affinity in scheduling and the affinity of realtime thread group associated with thread is empty.

StaticUnsupportedOperationException - when thread a normal Java thread and the scheduler does not support promoting normal java threads.

Parameters:

thread - The thread to promote to realtime scheduling.

eligibility - A SchedulingParameters instance such as PriorityParameters for a PriorityScheduler.

Since:

RTSJ 2.0

addToFeasibility

@Deprecated
protected abstract boolean addToFeasibility(Schedulable schedulable)

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

addToFeasibility adds the provided schedulable object to the set of schedulable objects that take part in feasibility analysis. This means that the schedulable's scheduling, release, memory, and processing group parameters will be taken into account for the feasibility analysis of the overall system.

Throws:

StaticIllegalArgumentException - if schedulable is null or schedulable is neither RealtimeThread nor AsyncBaseEventHandler.

Parameters:

schedulable - A schedulable object, must not be null.

Returns:

true iff the resulting system is feasible.

removeFromFeasibility

@Deprecated
protected abstract boolean removeFromFeasibility(Schedulable schedulable)

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

removeFromFeasibility removes the provided schedulable object from the set of schedulable objects that take part in feasibility analysis. This means that the schedulable's scheduling, release, memory, and processing group parameters will not longer be taken into account for the feasibility analysis of the overall system.

Throws:

StaticIllegalArgumentException - if schedulable is null or schedulable is neither RealtimeThread nor AsyncBaseEventHandler.

Parameters:

schedulable - A schedulable object, must not be null.

Returns:

true if schedulable was successfully removed from the set, false if it could not be removed since it was not part of the set.

setIfFeasible

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

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

setIfFeasible first performs a feasibility analysis using the new release and memory parameters for schedulable. If the resulting system is feasible, the release and memory parameters will be replaced.

Throws:

StaticIllegalArgumentException - if schedulable is null, release is null, or the parameter values are not compatible with the scheduler associated to schedulable.

IllegalAssignmentError - if release or memory and schedulable reside in memory areas whose objects cannot refer to one another (in both directions).

IllegalThreadStateException - If the old release parameters are periodic, the new release parameters are not periodic, and the schedulable object is currently blocked in waitForNextPeriod or waitForNextPeriodInterruptible.

Parameters:

schedulable - A schedulable object whose parameters should be changed.

release - the new release parameters. If null, the default value for the associated scheduler will be used.

memory - the new memory parameters. If null, the default value for the associated scheduler will be used. The default value for PriorityScheduler is null.

Returns:

true iff the resulting system is feasible and the new release and memory parameters have been activated. false if the resulting system is not feasible, no changes are made in this case.

setIfFeasible

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

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

setIfFeasible first performs a feasibility analysis using the new release, memory, and group parameters for schedulable. If the resulting system is feasible, the release, memory, and group parameters will be replaced.

Throws:

StaticIllegalArgumentException - if schedulable is null, release is null, or the parameter values are not compatible with the scheduler associated to schedulable.

IllegalAssignmentError - if release, memory or group and schedulable reside in memory areas whose objects cannot refer to one another (in both directions).

IllegalThreadStateException - If the old release parameters are periodic, the new release parameters are not periodic, and the schedulable object is currently blocked in waitForNextPeriod or waitForNextPeriodInterruptible.

Parameters:

schedulable - A schedulable object whose parameters should be changed. Must not be null.

release - the new release parameters. Must not be null.

memory - the new memory parameters. If null, the default value for the associated scheduler will be used. The default value for PriorityScheduler is null.

group - the new processing group parameters. If null, the default value for the associated scheduler will be used. The default value for PriorityScheduler is null.

Returns:

true iff the resulting system is feasible and the new release, memory, and group parameters have been activated. false if the resulting system is not feasible, no changes are made in this case.

setIfFeasible

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

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

setIfFeasible first performs a feasibility analysis for schedulable using the new scheduling, release, memory, and group parameters. If the resulting system is feasible, the scheduling, release, memory and group parameters of schedulable will be replaced.

Throws:

StaticIllegalArgumentException - if schedulable is null, release is null or the parameter values are not compatible with the scheduler associated to schedulable.

IllegalAssignmentError - if the parameters or the schedulable reside in memory areas whose objects cannot refer to one another (in both directions).

IllegalThreadStateException - if the old release parameters are periodic, the new release parameters are not periodic, and the schedulable object is currently blocked in waitForNextPeriod or waitForNextPeriodInterruptible.

Parameters:

schedulable - a schedulable object whose parameters should be changed. Must not be null.

scheduling - the new scheduling parameters.

release - the new release parameters. Must not be null.

memory - the new memory parameters. If null, the default value for the associated scheduler will be used. The default value for PriorityScheduler is null.

group - the new processing group parameters. If null, the default value for the associated scheduler will be used. The default value for PriorityScheduler is null.

Returns:

true if the resulting system is feasible and the new scheduling, release, memory, and group parameters have been activated. false if the resulting system is not feasible, no changes are made in this case.

getDefaultScheduler

public static Scheduler getDefaultScheduler()

getDefaultScheduler returns a reference to the default scheduler, which is an instance of PriorityScheduler.

Returns:

PriorityScheduler.instance()

setDefaultScheduler

public static void setDefaultScheduler(Scheduler scheduler)

setDefaultScheduler sets the default scheduler to the given scheduler.

Parameters:

scheduler - the new default scheduler. null to leave the default scheduler unchanged.

currentSchedulable

public static Schedulable currentSchedulable()

Gets the current execution context when called from a Schedulable execution context.

Throws:

ClassCastException - when the caller is not a Schedulable

Returns:

the current Schedulable.

Since:

RTSJ 2.0

getPolicyName

public abstract String getPolicyName()

getPolicyName returns the name of this scheduling policy. The result must be in a memory area assignable to the caller's current allocation environment.

Returns:

the name of this policy.

isFeasible

@Deprecated
public abstract boolean isFeasible()

Deprecated. as of RTSJ 2.0, because the framework for feasibility analysis is inadequate.

isFeasible checks if the current set of schedulable objects that take part in feasibility analysis form a feasible set

Returns:

true iff the system can be proven to be feasible, false if not.

fireSchedulable

@Deprecated
public abstract void fireSchedulable(Schedulable schedulable)
                                          throws UnsupportedOperationException

Deprecated. since RTSJ 2.0

Fire a release for the given schedulable object.

Throws:

UnsupportedOperationException - is thrown if the scheduler cannot fire a release of schedulable.

Parameters:

schedulable - a schedulable object.

inSchedulableExecutionContext

public static boolean inSchedulableExecutionContext()

Determines whether the current calling context is a Schedulable: RealtimeThread or AsyncBaseEventHandler.

Returns:

true when yes and false otherwise.

Since:

RTSJ 2.0

createDefaultSchedulingParameters

protected SchedulingParameters createDefaultSchedulingParameters()

Create a default SchedulingParameters instance for this scheduler. 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.

Throws:

IllegalTaskStateException - when the current task is using a scheduler that does not support null scheduling parameters.

Returns:

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