Stack resource policy

The Stack Resource Policy (SRP) is a resource allocation policy used in real-time computing, used for accessing shared resources when using earliest deadline first scheduling. It was defined by T. P. Baker. SRP is not the same as the Priority ceiling protocol which is for fixed priority tasks (FP).

The Stack Resource Policy (SRP) is a resource allocation policy used in real-time computing, used for accessing shared resources when using earliest deadline first scheduling. It was defined by T. P. Baker. SRP is not the same as the Priority ceiling protocol which is for fixed priority tasks (FP). C_R(V_R) = max(\{0\} \cup \{\pi(J) | V_R There is also a system ceiling \pi' which is the maximum of all current ceilings of the resources. \pi' = max(\{C_R(i) | i = 1,...,m\} \cup \{\pi(J_c)\}) Any task T_i that wishes to preempt the system must first satisfy the following constraint: \pi' This can be refined for Operating System implementation (as in MarteOS) by removing the multi-unit resources and defining the stack resource policy as follows All tasks are assigned a preemption level, in order to preserve the ordering of tasks in relation to each other when locking resources. The lowest relative deadline tasks are assigned the highest preemption level. Each shared resource has an associated ceiling level, which is the maximum preemption level of all the tasks that access this protected object. The system ceiling, at any instant in time, is the maximum active priority of all the tasks that are currently executing within the system. A task is only allowed to preempt the system when its absolute deadline is less than the currently executing task and its preemption level is higher than the current system ceiling. ==References==

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