ej.hrt

Class Task

java.lang.Object

ej.hrt.Task

public abstract class Task
extends java.lang.Object

A Task is a periodic cyclic task. Each task allocates a new thread of execution. This is used for real-time systems.

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_HRT_TASK_PRIORITY
static int	MIN_HRT_TASK_PRIORITY

Constructor Summary

Constructors

Constructor and Description
Task(java.lang.String name, long periodMin, int priority) Creates a cyclic task with a deadline equals to periodMin.
Task(java.lang.String name, long periodMin, long deadline, int priority) Creates a cyclic task.

Method Summary

Modifier and Type	Method and Description
java.lang.Thread	asThread()
static Task	currentTask() Returns a reference to the currently executing Task object. If the current thread is not a Task instance, this method returns null.
long	getCurrentWCA()
static long	getCurrentWCA(int taskUID) Calls the getCurrentWCA() method of the task with the specified UID.
long	getCurrentWCET()
static long	getCurrentWCET(int taskUID) Calls the getCurrentWCET() method of the task with the specified UID.
long	getDeadline() Gets the deadline of the task.
java.lang.String	getName() Gets the name of the task.
int	getNbDeadlinesReached()
static int	getNbDeadlinesReached(int taskUID) Calls the getNbDeadlinesReached() method of the task with the specified UID.
long	getPeriod() Gets the minimum period of the task.
int	getPriority() Gets the priority of the task.
int	getUID() Gets the unique ID of this task.
boolean	isInRescueMode() Tests if this task is in rescue mode.
static boolean	isInRescueMode(int taskUID) Calls the isInRescueMode() method of the task with the specified UID.
void	outOfResource(DeadlineException exception) Method called when this Task terminates due to the given uncaught DeadlineException exception.
void	outOfResource(WCAException exception) Method called when this Task terminates due to the given uncaught WCAException exception.
static void	registerCyclicTask(int taskUID, long increment, long period) Calls the registerCyclicTask(long, long) method of the task with the specified UID.
void	registerCyclicTask(long increment, long period) Starts a task cycle in increment nanoseconds and then every period nanoseconds. If the task is already registered as a cyclic task, this method modifies timing configuration.
abstract void	run() Starting the task causes this method run() to be called in a separately executing thread.
void	start() Starts a task cycle.
static void	start(int id) Calls the start() method of the task with the specified UID.
static void	start(Task[] tasks) Starts all the provided tasks at the very same time.
void	uncaughtException(java.lang.Throwable exception) Method called when this Task terminates due to the given uncaught exception.
void	unregisterCyclicTask() Disables the automatic start for this task.
static void	unregisterCyclicTask(int taskUID) Calls the unregisterCyclicTask() method of the task with the specified UID.

Methods inherited from class java.lang.Object

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

Field Detail

MIN_HRT_TASK_PRIORITY

public static final int MIN_HRT_TASK_PRIORITY

See Also:

Constant Field Values

MAX_HRT_TASK_PRIORITY

public static final int MAX_HRT_TASK_PRIORITY

See Also:

Constant Field Values

Constructor Detail

Task

public Task(java.lang.String name,
            long periodMin,
            int priority)

Creates a cyclic task with a deadline equals to periodMin. Equivalent to new Task(name, periodMin, periodMin, priority).

Parameters:

name - the name of the task

periodMin - the minimum period of the task (in nanoseconds)

Throws:

java.lang.IllegalArgumentException - if the given priority is not in the range MIN_HRT_TASK_PRIORITY to MAX_HRT_TASK_PRIORITY.

HRTException - if the system is not in initialization mode.

Task

public Task(java.lang.String name,
            long periodMin,
            long deadline,
            int priority)

Creates a cyclic task. If deadline is equals to 0, system will not check for deadline exception for this task.

Parameters:

name - the name of the task

periodMin - the minimum period of the task (in nanoseconds)

deadline - the duration of the deadline of the task (in nanoseconds)

Throws:

java.lang.IllegalArgumentException - if deadline is higher than periodMin

java.lang.IllegalArgumentException - if the given priority is not in the range MIN_HRT_TASK_PRIORITY to MAX_HRT_TASK_PRIORITY.

HRTException - if the system is not in initialization mode.

Method Detail

getName

public java.lang.String getName()

Gets the name of the task.

Returns:

the name of the task

getPriority

public int getPriority()

Gets the priority of the task.

Returns:

the priority of the task

getPeriod

public long getPeriod()

Gets the minimum period of the task.

Returns:

the minimum period of the task (in nanoseconds)

getDeadline

public long getDeadline()

Gets the deadline of the task.

Returns:

the duration of the deadline of the task (in nanoseconds)

start

public final void start()

Starts a task cycle. If this thread is running, the start is recorded and performed later.

Throws:

HRTException - if the task is registered as cyclic task

start

public static void start(Task[] tasks)

Starts all the provided tasks at the very same time.

Throws:

HRTException - if one the tasks is registered as cyclic task

run

public abstract void run()

Starting the task causes this method run() to be called in a separately executing thread. Subclasses of Task must override this method.

outOfResource

public void outOfResource(WCAException exception)

Method called when this Task terminates due to the given uncaught WCAException exception. This method invoke the uncaughtException() method with the given exception.
This method should be overridden by subclasses in order to define behavior of the task in downgraded mode.
Any exception thrown by this method will be ignored by the system.

Parameters:

exception - the exception

outOfResource

public void outOfResource(DeadlineException exception)

Method called when this Task terminates due to the given uncaught DeadlineException exception. This method invoke the uncaughtException() method with the given exception.
This method should be overridden by subclasses in order to define behavior of the task in downgraded mode.
Any exception thrown by this method will be ignored by the system.

Parameters:

exception - the exception

uncaughtException

public void uncaughtException(java.lang.Throwable exception)

Method called when this Task terminates due to the given uncaught exception. This method invoke the printStackTrace() method on the given exception.
This method should be overridden by subclasses in order to define behavior of the task in downgraded mode.
Any exception thrown by this method will be ignored by the system.

Parameters:

exception - the exception

getUID

public int getUID()

Gets the unique ID of this task.

Returns:

the unique ID of this task

start

public static void start(int id)

Calls the start() method of the task with the specified UID.

Parameters:

id - the unique ID of the task to start

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

HRTException - if the task is registered as cyclic task

registerCyclicTask

public void registerCyclicTask(long increment,
                               long period)

Starts a task cycle in increment nanoseconds and then every period nanoseconds.
If the task is already registered as a cyclic task, this method modifies timing configuration.

Parameters:

increment - time before first start in nanoseconds

period - time between each starts in nanoseconds

Throws:

PeriodException - if period is lower than period of this task.

unregisterCyclicTask

public void unregisterCyclicTask()

Disables the automatic start for this task.

isInRescueMode

public boolean isInRescueMode()

Tests if this task is in rescue mode.

Returns:

true if the task is in rescue mode, false otherwise.

getCurrentWCET

public long getCurrentWCET()

Returns:

Maximum cycle time for current execution in nanoseconds.

getCurrentWCA

public long getCurrentWCA()

Returns:

Maximum cycle allocation for current execution in bytes.

getNbDeadlinesReached

public int getNbDeadlinesReached()

Returns:

number of deadlines reached for current execution.

asThread

public java.lang.Thread asThread()

Returns:

the Thread instance that will execute this task.

registerCyclicTask

public static void registerCyclicTask(int taskUID,
                                      long increment,
                                      long period)

Calls the registerCyclicTask(long, long) method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

unregisterCyclicTask

public static void unregisterCyclicTask(int taskUID)

Calls the unregisterCyclicTask() method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

isInRescueMode

public static boolean isInRescueMode(int taskUID)

Calls the isInRescueMode() method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

getCurrentWCET

public static long getCurrentWCET(int taskUID)

Calls the getCurrentWCET() method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

getCurrentWCA

public static long getCurrentWCA(int taskUID)

Calls the getCurrentWCA() method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

getNbDeadlinesReached

public static int getNbDeadlinesReached(int taskUID)

Calls the getNbDeadlinesReached() method of the task with the specified UID.

Parameters:

taskUID - the unique ID of the task

Throws:

java.lang.IllegalArgumentException - if the specified UID is not valid

currentTask

public static Task currentTask()

Returns a reference to the currently executing Task object.
If the current thread is not a Task instance, this method returns null.