Task Performance
Concurrency and Deadlocks
Objective(s):
At the end of the exercise, the students should be able to:
Assess the common concurrency mechanisms; and
Analyze the deadlock prevention and avoidance strategies as well as the detection approach.
Instructions:
Analyze the illustrations below. Then, answer the following items. Search for related literature
and/or relative studies that would support your answers. Cite your references accordingly. (55
points)
1. Describe the deadlock scenario illustrated above based on your understanding. (5
points)
Deadlock is a situation where a set of processes are blocked because each process is
holding a resource and waiting for another resource acquired by some other process.
2. What do you think would happen if both Process P and Q need to get the same
resource? (5 points)
When process P issues the signal to wake up process Q, P then waits, either for Q to
leave the monitor or on some other condition.
3. Which concurrency mechanism would you suggest that might prevent the deadlock
situation above? Rationalize your answer. (5 points)
Eliminate Mutual Exclusion - It is not possible to dis-satisfy the mutual exclusion because
some resources, such as the tape drive and printer, are inherently non-shareable.
4. Define in detail the Execution Paths 2 to 6. (5 items x 3 points)
Execution Paths 2 – Process Q acquires to Release B down to Get B and Pass the Process
Q releases Resource A and B showing Paths 6.
Example: Execution Path 1 – Process Q acquires Resource B and then Resource A. Process Q
then releases Resource B and A, respectively.
5. Do Execution Paths 3 and 4 encompass the first three conditions for a deadlock to
occur? Explain your answer. (5 points)
They Execute the Deadlock inevitable
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6. If you are to implement deadlock prevention before the processes above reach the
critical section, would it be an indirect method or an indirect method? Why? (5 points)
An indirect method – because the purposes of deadlock prevention, a system can be
modeled as a collection of limited resources, which can be partitioned into different
categories, to be allocated to a number of processes, each having different needs.
7. Which deadlock avoidance approach would you suggest for the given situation above
and why? (5 points)
Safe and Unsafe States - In deadlock avoidance, the request for any resource will be
granted if the resulting state of the system doesn't cause deadlock in the system. The
state of the system will continuously be checked for safe and unsafe states. The simplest
and most useful approach states that the process should declare the maximum number
of resources of each type it may ever need. The Deadlock avoidance algorithm examines
the resource allocations so that there can never be a circular wait condition.
8. Would you agree that deadlock is relative to the number of processes and available
resources in an operating system? Why or why not? (5 points)
Yes, because one process is waiting for the resource, which is held by the second
process, which is also waiting for the resource held by the third process etc.
9. If you are asked to reconstruct the progress diagram above to eliminate the critical
section, which is the deadlock-inevitable region, which aspect(s) or area(s) would you
modify? Explain how the modification eliminates the deadlock. (5 points)
Nothing, because I see in the graph that the diagram is good for me.
https://www.geeksforgeeks.org/introduction-of-deadlock-in-operating-system/
https://www.cs.uic.edu/~jbell/CourseNotes/OperatingSystems/7_Deadlocks.html
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https://www.coursehero.com/file/117930304/Concurrency-and-Deadlocksdocx/
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