Operating System - Process Deadlock Condition

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What is Deadlock in OS?

In multiprogramming environment, In a multiprogramming environment, a process requests resources held by a second process. If Second process requests resources held by the first process. Both Requesting process gets in a long waiting state. This blocking situation is called deadlock.

Before understanding a deadlock, Let us understand the resource types, process accesses and releases a resource

Resource types and allocation to process

Examples of resource types are: CPU cycles, files, I/O devices and Memory space. Suppose the system has two CPUs, then the resource type CPU has two instances. When a process requests an instance of the resource type, then the available instances are allocated to the requesting process.

Process - Normal Mode of operation

A process must request a resource before using it and release the resource after using it. The following is the normal mode of operation:

  • Request : If the request is not granted immediately, then the process must wait until it gets that resource.
  • Use : After the request is granted, the process uses it.
  • Release : When the process has completed the work with that resource, then the resource must be released.

If a process A requests resources but the resources are blocked by a process B which in turn wait for resources blocked by process A, then it causes a deadlock.


<<Previous - OS Multi Level Queue Scheduling

Next - Necessary Conditions For Deadlock >>







Operating System - Process Deadlock Condition

<<Previous - Multi Level Queue Scheduling

Next - Necessary Conditions For Deadlock >>





What is Deadlock in OS?

In multiprogramming environment, In a multiprogramming environment, a process requests resources held by a second process. If Second process requests resources held by the first process. Both Requesting process gets in a long waiting state. This blocking situation is called deadlock.

Before understanding a deadlock, Let us understand the resource types, process accesses and releases a resource

Resource types and allocation to process

Examples of resource types are: CPU cycles, files, I/O devices and Memory space. Suppose the system has two CPUs, then the resource type CPU has two instances. When a process requests an instance of the resource type, then the available instances are allocated to the requesting process.

Process - Normal Mode of operation

A process must request a resource before using it and release the resource after using it. The following is the normal mode of operation:

  • Request : If the request is not granted immediately, then the process must wait until it gets that resource.
  • Use : After the request is granted, the process uses it.
  • Release : When the process has completed the work with that resource, then the resource must be released.

If a process A requests resources but the resources are blocked by a process B which in turn wait for resources blocked by process A, then it causes a deadlock.


<<Previous - OS Multi Level Queue Scheduling

Next - Necessary Conditions For Deadlock >>







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