This document discusses deadlocks in operating systems. A deadlock occurs when all processes are blocked from accessing resources and communicating due to resource deficiencies or conflicts. Resources can be consumable, used by only one process and then depleted; sharable, used by multiple processes simultaneously; or serially reusable, used by one process at a time but not depleted. For a deadlock to occur there must be mutual exclusion of resources, a hold and wait condition, no preemption of resources, and a circular wait chain of processes. Operating systems aim to prevent deadlocks through careful resource management and include recovery systems in case a deadlock still occurs.

1. Computer Science
Cape – Unit 2 – Module 3: Operating Systems & Computer Networks
Specific objective: Describe the function of the operating system

2. Objective
• At the end of the lesson you should be able to:
• Discuss the concept of Deadblock in relation to operating systems

3. What is a Deadlock?
• Deadlock refers to the blocking of all processes that utilize system resources
or communicate with each other.
• This deadlock also occurs when there is no efficient solution to a resource
deficiency or a conflict between two or more processes.

4. Resources
• Processor resources are split in three categories;
• Consumable
• Sharable
• Serially reusable

5. Sharable Resources
• Sharable resources can be used by more than one process at a time

6. Consumable Resources
• Consumable resources can only be used by one process, and the resource
gets “used up”.

7. Serially Reusable Resources
• These are used by one process at a time and not depleted by that use.
• In the OS, processes are initially allocated resources that they occupy and
release for other processes to utilize.
• As is expected, where a process holds its pre allocated resource and requests
another a Deadlock is bound to take occur.

8. Conditions for Deadlock
• Mutual exclusion
• The resource is available to only process at a time.
• Hold and wait
• Allocated resources being in a suspended or held state by a process while awaiting other resource
assignments.
• No preemption
• It is not possible to pre plan when a resource is going to be available
• Circular wait
• This exists in a closed chain of processes where the current process holds the resource needed for the
next process and so on.

9. Methods for Handling Deadlocks
• Guard against system deadlocks.
• Create and implement a recovery system in the event of a deadlock.