Hardware Reference
In-Depth Information
J
J
J
J
Number in the node = scheduled task
1
2
3
4
a
4
1
1
0
Number outside the node = finishing time
i
C
2
1
2
2
i
J
= task that misses its deadline
i
d
75
6
4
i
= feasible schedule
6
3
2
2
1
2
3
4
6
4
4
J
2
J
3
6
4
1
3
4
1
2
J
J
4
J
2
5
6
6
6
3
1
3
1
3
J
3
J
J
7
1
3
1
Figure 3.10
Example of search performed by Bratley's algorithm.
For this reason, Bratley's algorithm can only be used in off-line mode, when all task
parameters (including the arrival times) are known in advance. This can be the case
of a time-triggered system, where tasks are activated at predefined instants by a timer
process.
As in most off-line real-time systems, the resulting schedule produced by Bratley's
algorithm can be stored in a data structure, called
task activation list
. Then, at run
time, a dispatcher simply extracts the next task from the activation list and puts it in
execution.
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