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Asynchronous Indication of the Completion of a Requested Function

IP.com Disclosure Number: IPCOM000080001D
Original Publication Date: 1973-Oct-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Etchison, KL: AUTHOR

Abstract

In the design of an operating system (OS), it is desirable to allow for as much parallel execution of logic as possible. In OS Input Output Subsystem (IOS) is an example of such allowance for parallel execution.

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Asynchronous Indication of the Completion of a Requested Function

In the design of an operating system (OS), it is desirable to allow for as much parallel execution of logic as possible. In OS Input Output Subsystem (IOS) is an example of such allowance for parallel execution.

The problem program requests an I/O operation to be done by the system. The system processes the request as far as possible with the resources available and returns control to the problem program. As additional resources become available, (i.e., channels, devices, etc.) processing of the request will proceed asynchronously to the requesting task. The figure shows typical processing of a request in this manner.

Exit 1, if taken, will always be to the requesting program. Exits 2-4 will be to the previous routing entering the logic. If all resources were available, Exit 4 would be to the requesting program. If all resources except resource 2 were available, Exit 4 would be to the resource 2 allocation routine.

This type of resource allocation is usually done via appendages, where the resource allocation routine is given the address at logic to be executed when the resource becomes available, if it is not immediately so. The requesting routine is informed via return codes whether the resource was immediately available.

By extending the meaning at the return codes to include the type of exit required, there is no need to pass a reentry point address. The return address passed as part of the link...