a. Three processes share four resource units that can be reserved and released only one at a time. Each process needs a maximum of two units. Show that a deadlock cannot occur. b. N processes share M resource units that can be reserved and released only one at a time. The maximum need of each process does not exceed M, and the sum of all maximum needs is less than M + N. Show that a deadlock cannot occur.

Last solution had mistakes: For these questions, assume that memory partitions can be subdivided; multiple processes may fit in a partition if there is room. For example, if we had a 30-MB partition and a 20-MB process that fits in the partition, the partition’s new size is 10 MB after placing the process in it. If a second, 8-MB process arrives, we may place it in the partition, leaving 2 MB free in the partition. (The original memory partition then contains a 10-MB and an 8-MB process.) Consider a swapping system where memory has partitions of the following sizes: 180 MB, 100 MB, 40 MB, 200 MB, 300 MB, and 150 MB (in order). For first fit, how are processes of sizes 180 MB, 30 MB, 150 MB, 80 MB, 100 MB, and 70 MB placed (in order)? Indicate which requests (if any) cannot be satisfied. Repeat question (a) for best fit. Repeat question (a) for worst fit.

Suppose that an operating system supports two kinds of sequential processes: high-priority interactive processes, and low-priority non-interactive processes. The behavior of the high-priority processes is to alternate between periods of computation of duration Tc and periods of blocking (waiting for input) of duration Tb. The behavior of the low-priority processes is to compute constantly, with no blocking. The operating system’s scheduling policy is round-robin with a quantum q, where Tc < q. Scheduling decisions are made only when a quantum expires, or when the running process blocks. The scheduler selects a low-priority process to run only if no high-priority processes are ready. Suppose there is one high-priority process and one low-priority process in the system, and that both processes will run for a long time. For what fraction of the time does the low-priority process run?

a. Three processes share four resource units that can be reserved and released only one at a time. Each process needs a maximum of two units. Show that a deadlock cannot occur. b. N processes share M resource units that can be reserved and released only one at a time. The maximum need of each process does not exceed M, and the sum of all maximum needs is less than M + N. Show that a deadlock cannot occur.

Producer-consumer problem is a common paradigm for cooperating processes. A producer process produces information that is consumed by a consumer process. One solution to the producer-consumer problem uses shared memory. To allow producer and consumer processes to run concurrently, there must be available a buffer of items that can be filled by the producer and emptied by the consumer. This buffer will reside in a region of memory that is shared by the producer and consumer processes. A producer can produce one item while the consumer is consuming another item. The producer and consumer must be synchronized, so that the consumer does not try to consume an item that has not yet been produced. Write a bash script to simulate producer-consumer problem using semaphores.

73. Deadlock prevention is a set of methods : a. to ensure that at least one of the necessary conditions cannot hold b. to ensure that all of the necessary conditions do not hold c. to decide if the requested resources for a process have to be given or not d. to recover from a deadlock

Three processes that share five resources of the same kind make constitute a system. For each process, a maximum of two resources are needed. Establish that the system is free of deadlocks.