OPERATING SYSTEMS - LECTURE -20- DEADLOCK DETECTION (SEVERAL INSTANCES OF A RESOURCE TYPE) BCA- S3.
Several Instances of a Resource Type
The wait-for graph scheme is not applicable to a resource-allocation system with multiple instances of each resource type. The algorithm employs several time-varying data structures that are similar to those used in the banker’s algorithm .
• Available. A vector of length m indicates the number of available resources of each type.
• Allocation. An n × m matrix defines the number of resources of each type currently allocated to each process.
• Request. An n × m matrix indicates the current request of each process. If Request[i][j] equals k, then process Pi is requesting k more instances of
resource type Rj .
The detection algorithm described here simply investigates every possible allocation sequence for the processes that remain to be completed. Compare this algorithm with the banker’s algorithm.
This algorithm requires an order of m × n2 operations to detect whether the system is in a deadlocked state.