Hardware Reference
In-Depth Information
The task period;
The relative deadline, specified by the user;
The absolute deadline, computed by the kernel at the arrival time;
The task utilization factor (only for periodic tasks);
A pointer to the process stack, where the context is stored;
A pointer to a directed acyclic graph, if there are precedence constraints;
A pointer to a list of shared resources, if a resource access protocol is provided
by the kernel.
Task Control Block
task identifier
task address
task type
criticalness
priority
state
computation time
period
relative deadline
absolute deadline
utilization factor
context pointer
precedence pointer
resource pointer
pointer to the next TCB
Figure 10.8
Structure of the Task Control Block.
In addition, other fields are necessary for specific features of the kernel. For exam-
ple, if aperiodic tasks are handled by one or more server mechanisms, a field can be
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