• Exercise 1, demo of the basic AADLInspector analysis features
  
• Exercise 2, first handouts with AADLInspector
  
• Exercise 3, Mars Path Finder, analysis of a model with shared data
  
• Exercise 4, Rosace, analysis of a model with data flow
  
• References
  
• SOLUTIONS

This set of exercises show how to use AADLInspector to run scheduling analysis with Cheddar.
The slides of the lecture to do those exercises can be downloaded here .


Installation procedure

To do the following exercises, you need AADLInspector. You can either download and install AADLInspector from http://www.ellidiss.com/downloads on your laptop (for Windows or Linux targets only). You can also use a virtual machine (vdi file named "cheddar_tutorial.vdi") if you are able to run Virtual Box. The cheddar_tutorial.vdi file is there . When launched, you must log to the machine with "cheddar" as login name (same string for the password). Then, to have AADLInspector in your path, run the following command:

source TEST_AI/ai.bash




Running procedure

For windows target, just click on the AADLInspector icon. For Linux station, use the following command:

AADLInspector&

Exercise 1, demo of the basic AADLInspector analysis features

1. Download the following AADL model.
2. Save those files in a specific folder. Those files are composing an AADLInspector project: the file .aic allows AADLInspector to load all AADL files composing your model from the menu File/Load.
3. From File/Load, load the project.
4. With the Static analysis/Parse and Instanciante LMP button, verify the AADL model. What is the root component of this model ? Give the instance model graph.
5. To perform a scheduling analysis, the processor component has to be extended with few properties. Add to the cpu_leon2 component the following properties:

   PROPERTIES
      Scheduling_protocol => (rate_monotonic_protocol);
   

6. Compute the scheduling of this thread set with Cheddar by the button Timing Analysis/Simulation timelines (Cheddar). From this simulation, compute with Cheddar the response times of the threads by the button Simulation Tests (Cheddar).
7. Compute theoretical worst case thread response times, always with Cheddar but with the button Timing Analysis/Theoretical Tests (Cheddar).
8. Open the task response thread summary panel.
9. Do a simulation with Marzhin.
10. Explain why we have different response times for each thread on this panel?
11. Update the Scheduling_protocol property for subcomponent cpu with value posix_1003_highest_priority_first_protocol
    
12. Do again the questions 6, 7 and 8.

Exercise 2, first handouts with AADLInspector

package sampling_coms

public

  thread writer
  end writer;

  thread reader
  end reader;

  thread implementation reader.impl
  end reader.impl;

  thread implementation writer.impl
  end writer.impl;

  process application
  end application;

  process implementation application.impl
  end application.impl;

  processor cpu
  end cpu;

  system smpl
  end smpl;

  system implementation smpl.impl
  subcomponents
    process1 : process application.impl;
    cpu1     : processor cpu;
  properties
    Actual_Processor_Binding => (reference(cpu1)) applies to process1;
  end smpl.impl;

end sampling_coms;

1. Change the definition of the threads and the process above in order to:
   • Define a periodic thread called writer with a deadline and a period of 10 ms. The priority is 20. The execution time of this thread is about 1 ms in the best case and 3 ms in the worst case.
   • Define a periodic thread called reader with a deadline and a period of 20 ms. The execution time of this thread is about 2 ms. The priority is 10.
2. Check correctness of the model with LMP.
3. In order to perform scheduling analysis, extend your modele with the following property:
   

   properties
      Scheduling_Protocol=>(POSIX_1003_HIGHEST_PRIORITY_FIRST_PROTOCOL);
   

   
   
4. Perform the scheduling analysis with AADLInspector.

1. From the model of the previous question and without introducing new component type, extend the model in order to declare 3 writers and 2 readers with the following properties:
   • Writer 1 : Deadline = Period = 40 ms ; execution time ranging 1 and 5 ms ; Priority = 1
   • Writer 2 : Deadline = Period = 20 ms ; execution time ranging 1 and 4 ms ; Priority = 2
   • Writer 3 : Deadline = Period = 20 ms ; execution time ranging 1 and 2 ms ; Priority = 3
   • Reader 1 : Deadline = Period = 40 ms ; execution time ranging 1 and 3 ms ; Priority = 4
   • Reader 2 : Deadline = Period = 40 ms ; execution time ranging 1 and 2 ms ; Priority = 5
2. Verify your model by simulations with AADLInspector.

1. Change your previous model by adding a data component and the required connections to the threads. For this data component, define the following property:
   

   properties
      Concurrency_Control_Protocol => PCP;
   

   
   
   
2. Once updated, analyze your model with AADLInspector to locate locks and unlocks of the data component.

Exercise 3, Mars Path Finder, analysis of a model with shared data

• All the tasks are periodic, synchronous, and have deadlines equal to periods.
• FORECAST is sometimes released for a job of 50 ms, and sometimes for a job of 75 ms, depending of the size of the payload to handle.
• Priority levels expressed bellow are VxWorks priorities : the lower the value is, the higher the priority level is.
• DATA, CONTROL, MESURE and FORECAST required a shared data which is accessed by a critical section during all their execution times (i.e all their capacity/WCET). To reduce costs, those critical sections were implemented with a mutex that did not use inheritance priority protocol such as PIP or PCP. In order to define those critical sections without PIP/PCP, simply do not add the Concurrency_Control_Protocol property when defining your data component.
  
  

1. During the mission of Mars PathFinder, operators noticed that some deadlines were missed, leading to frequent reboots of the hardware. Design an AADL model to discover what are the missed deadlines and why those threads where not able to meet their deadlines.
2. How to solve this issue? Apply it on your AADL model.

Exercise 4, Rosace, analysis of a model with data flow

• Download the AADL model. that represents a possible AADL design for the functional model shown above.
• Note the use of Feature Groups and Thread Groups.
• Identify what are the main missing AADLconstructs.

• Add missing connections in THREAD GROUP IMPLEMENTATION Flight_Software.impl
• Run scheduling analysis.

• Add Priority and/or Dispatch_Offset properties in order to ensure a proper ordering of the threads regarding the dataflow logics.
• Check with the scheduling analysis tools.

References