Nested resource control using locking and unlocking routines with use counter for plural processes

• US 4,435,766 A
• Filed: 06/16/1981
• Issued: 03/06/1984
• Est. Priority Date: 06/16/1981
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Jeffries, Kenneth L., Kilpatrick, Paul J., Haber, Judith G.
• Primary Examiner(s): Zache, Raulfe B.
• Application Number:
  US06/274,113
• Time in Patent Office: 994 Days
• Field of Search: 364/200, 364/900 MS File, 364/300
• US Class Current: 710/200
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A mechanism allowing nested resource locks among a plurality of related programs is provided by means of a lock counter which is incremented and decremented as programs LOCK and UNLOCK a resource but the resource is not released until a count is zero. A separate LOCK counter is provided for each resource in the system.

Claims

1. A method of controlling a process lock on a resource, said method comprising:

nesting lock requests within a number of programs comprising a process;

maintaining said process lock through incrementing and decrementing a use counter from the initial process lock, during execution of a program, and calling up other programs within said process until said use counter is restored to its initial state prior to releasing said initial process lock.

2. A method of serializing access to a resource by a plurality of programs belonging to a common process comprising the steps of:

(a) defining a convention lock counter for association with a process;

(b) incrementing said counter whenever one of the programs in the process requests a lock;

(c) decrementing said counter whenever one of said programs requests an unlock; and

(d) releasing said resource only when said convention lock counter is zero.

3. A system for providing serialized access to a resource by a plurality of related programs in a multi-tasking environment including:

convention lock counter means associated with the resource;

means associated with said convention lock counter for incrementing said counter whenever a program requests a lock;

means associated with said convention lock counter for decrementing said counter whenever one of said programs requests an unlock; and

means responsive to said programs and associated with said convention lock counter for releasing said resource for access by a program unrelated to the related programs only when said convention lock counter is zero.

4. The system of claim 3 further including means connected to said resource for establishing and maintaining a wait queue for programs unrelated to the related programs when said unrelated programs request a lock.

7. The system of claim 4 further including means associated with each routine for priority ordering said programs in said wait queue.

5. In a multi-tasking interactive environment system means for controlling allocation of a plurality of resources among a plurality of processes where each process may encompass a plurality of routines which can request locks on a resource including:

control means for granting all requests for locks on a resource from one process before granting any requests from a different process.

6. The system of claim 5 wherein said control means for granting includes:

lock counter means associated with each resource;

means connected to the resource for incrementing the lock counter whenever any routine in a first process requests a lock;

means connected to the resource for decrementing the lock counter whenever any routine in the first process requests an unlock;

means associated with the resource for maintaining a wait list of any lock requesting routines not in the first process; and

means associated with the resource for honoring the lock request of a routine in said wait list only when said lock counter is zero.

8. The system of claim 6 further including means associated with each routine for priority ordering the wait list.