Monitoring Deadline Monitoring Deadline Misses in Periodic Real-Misses in Periodic Real-

time Threadstime Threads

Prepared By: Ebtesam Saleh-220060051Prepared By: Ebtesam Saleh-220060051Prepared For: Eng. Tasneem DarweshPrepared For: Eng. Tasneem Darwesh

University of PalestineFaculty of Applied Engineering and Urban Planning

Software Engineering Department

Concurrent and Real Time programming

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In many soft real-time systems applications will want to monitor any deadline misses, but take no action unless a certain threshold is reached.

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Monitoring Deadline Misses : interface

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ExampleExamplehealth monitor objechealth monitor objec

import javax.realtime.*; public class HealthMonitor { public void

persistentDeadlineMiss(Schedulable s); }

Monitoring Deadline Misses : interface

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import javax.realtime.*;class DeadlineMissHandler extends

AsyncEventHandler{

public DeadlineMissHandler(HealthMonitor mon, int threshold) { super(new PriorityParameters( PriorityScheduler.MAX_PRIORITY), null, null, null, null, null); myHealthMonitor = mon; myThreshold = threshold; } public void setThread(RealtimeThread rt) { myrt = rt; }

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public void handleAsyncEvent() { if(++missDeadlineCount < myThreshold) myrt.schedulePeriodic(); else myHealthMonitor.persistentDeadlineMiss(myrt);

}

private RealtimeThread myrt; private int missDeadlineCount = 0; private HealthMonitor myHealthMonitor; private int myThreshold; }

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• When the handler is executed, it increments the miss count and reschedules the thread.

• When the count reaches the threshold, it informs the health monitor and does not reschedule the thread.

Monitoring Deadline Misses

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it is not possible to pass the real-time thread as a parameter to the constructor of the handler, as the handler itself is needed before the real-time thread can be constructed.

Monitoring Deadline Misses

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setting up the real-time periodic thread

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setting up the real-time periodic thread

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Deadline miss handlers are schedulable objects. Consequently, they will compete for processor time with their associated schedulable objects according to their priorities. Hence, for the handler to have an impact on the (in this case) errant real-time thread, it must have a priority higher than the real-time thread. If the priority is lower, it will not run until the errant thread blocks.

Monitoring Deadline Misses

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Questions??Questions??