1. NET 424: REAL-TIME SYSTEMS (Practical Part)
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Tutorial 8: on lecture 6

2. Question 1
Consider the Priority Ceiling Protocol. Using this protocol, give a picture describing a run of three tasks on one processor: _ Task 1 has the highest priority. Task 1 arrives at time t=6. Task 1 consists of normal computation for 2 time units, followed by critical section 1 for 2 time units, followed by normal computation for 1 time unit. _ Task 2 has lower priority than Task 1. Task 2 arrives at time t=2. Task 2 consists of normal computation for 1 time unit, followed by critical section 2 for 3 time units, followed by normal computation for 1 time unit, followed by critical section 3 for 1 time unit, followed by normal computation for 1 time unit. .
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3. Question 1
_ Task 3 has the lowest priority. Task 3 arrives at time t=0. Task 3 consists of normal computation for 1 time unit, followed by critical section 3 for 2 time units, followed by normal computation for 1 time unit. Your picture should depict which task is executed (and the type of computation: either normal or the critical section the task is in) in the processor at which point in time, covering the interval from time t=0 until all work is done. You should also explicitly give any changes in the priority of the Tasks
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4. Answer R1 R1 T1 R2 R2 R2 R3 T2 R3 R3 T3
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5. Question 2 Basic inheritance protocol Ri ei Resource requirements
Ri ei Resource requirements
J [R1; 1]
J [R2; 1] J
J [R1; 4 [R2; 1.5]]
J [R2; 4]
T=1  J5  R2
T=3  J4  R1
T=11 J4  R2
T=11 J1 R1
T= 13 J2 R2
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6. Answer R1 J1 R2 J2 J3 R1 R1 R1 R1 R2 J4 R2 R2 R2 R2 J5
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7. The End
Any Questions ?
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