javax.realtime

Class Scheduler

java.lang.Object

javax.realtime.Scheduler

Direct Known Subclasses:

PriorityScheduler

public abstract class Scheduler
extends java.lang.Object

An instance of Scheduler manages the execution of schedulables.

Subclasses of Scheduler are used for alternative scheduling policies and should define an instance() class method to return the default instance of the subclass. The name of the subclass should be descriptive of the policy, allowing applications to deduce the policy available for the scheduler obtained via getDefaultScheduler(), e.g., EDFScheduler.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Scheduler() Creates an instance of Scheduler.

Method Summary

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

Creates an instance of Scheduler.

Method Detail

getDefaultScheduler

public static Scheduler getDefaultScheduler()

Gets a reference to the default scheduler.

Returns:

a reference to the default scheduler.

setDefaultScheduler

public static void setDefaultScheduler(Scheduler scheduler)

Sets the default scheduler. This is the scheduler given to instances of schedulables when they are constructed by a Java thread. The default scheduler is set to the required PriorityScheduler at startup.

Parameters:

scheduler - The Scheduler that becomes the default scheduler assigned to new schedulables created by Java threads. When null nothing happens.

Throws:

StaticSecurityException - when the caller is not permitted to set the default scheduler.

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

currentSchedulable

public static Schedulable currentSchedulable()

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

Returns:

the current Schedulable.

Throws:

java.lang.ClassCastException - when the caller is not a Schedulable

Since:

RTSJ 2.0

getPolicyName

public abstract java.lang.String getPolicyName()

Gets a string representing the policy of this. The string value need not be interned, but it must be created in a memory area that does not cause an illegal assignment error when stored in the current allocation context and does not cause a MemoryAccessError when accessed.

Returns:

a String object which is the name of the scheduling policy used by this.

addToFeasibility

@Deprecated
protected abstract 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.

Parameters:

schedulable - A reference to the given instance of Schedulable

Returns:

true, when the system is feasible after the addition, and false, when not.

Throws:

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

isFeasible

@Deprecated
public abstract boolean isFeasible()

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

Queries the system about the feasibility of the system currently being considered. The definitions of "feasible" and "system" are the responsibility of the feasibility algorithm of the actual Scheduler subclass.

Returns:

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

setIfFeasible

@Deprecated
public abstract 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.

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 ReleaseParameters changes 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 abstract 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.

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 abstract 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.

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().

removeFromFeasibility

@Deprecated
protected abstract 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.

Parameters:

schedulable - A reference to the given instance of Schedulable

Returns:

true, when the removal was successful, and 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 abstract void fireSchedulable(Schedulable schedulable)

Deprecated. RTSJ 2.0

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

Parameters:

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

Throws:

StaticUnsupportedOperationException - when the scheduler cannot release schedulable for execution.

reschedule

public abstract void reschedule(java.lang.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.

Parameters:

thread - The thread to promote to realtime scheduling.

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

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.

Since:

RTSJ 2.0

createDefaultSchedulingParameters

protected SchedulingParameters createDefaultSchedulingParameters()

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.

Returns:

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

Throws:

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

Since:

RTSJ 2.0