SOLUTIONS TO THE EXERCISES - Hard Real-Time Computing Systems: Predictable Scheduling Algorithms and Applications - page 478

C R (3) C R (2) C R (1) C R (0)

A 0 1 2 3

B 0 0 0 2

C - 0 2 3

Table 13.4 SRP resource ceilings resulting for Exercise 7.8.

SOLUTIONS FOR CHAPTER 8

8.1 We first note that the task set is feasible in fully preemptive mode, in fact

R 1 = C 1 =2 ≤ D 1

R (0)
2

= C 1 + C 2 =4

C 2 + 4
T 1

C 1 =4

R (1)
2

= ≤ D 2

R (0)
3

= C 1 + C 2 + C 3 =8

C 3 + 8
T 1

C 1 + 8
T 2

C 2 =10

R (1)
3

=

C 3 + 10
T 1

C 1 + 10
T 2

C 2 =12

R (2)
3

=

C 3 + 12
T 1

C 1 + 12
T 2

C 2 =12

R (3)
3

= ≤ D 2

Hence, by the result of Theorem 8.1, the feasibility of the task set in non-
preemptive mode can be verified by just checking the first job of each task,
when activated at its critical instant. The critical instant for task τ i occurs when
τ i is activated together with all higher priority tasks, and one unit after the
longest lower priority task.
Using Equation (8.1), the blocking times result to be B 1 =3, B 2 =3, B 3 =0,
and tasks response times can be computed as R i = S i + C i , where S i is given