Method and means for the sharing of data resources in a multiprocessing, multiprogramming environment

• US 4,399,504 A
• Filed: 10/06/1980
• Issued: 08/16/1983
• Est. Priority Date: 10/06/1980
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Watts, Vern L., Strickland, Jimmy P., Obermarck, Ronald L.
• Primary Examiner(s): Zache, Raulfe B.
• Application Number:
  US06/194,483
• Time in Patent Office: 1,044 Days
• Field of Search: 364/300, 364/200 MS File
• US Class Current: 710/200
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

Data resources are shared by applications executing on a plurality of central electronic complexes. Each complex of a pair includes a resource lock manager (IRLM) which maintains the hold and wait locks for applications executing on the complex and selected wait locks for the other complex. Selective communication of lock request information is controlled by hash tables maintained in synchronization in each IRLM, which denote the interest of each complex in each hash class of data resources.

Claims

1. A machine-implementable method for operating a computing system, including plural central electronic complexes processing work units of one or more programs concurrently to control access to data resources shared by at least two central electronic complexes with minimum communication of sharing control parameters, comprising the steps of:

maintaining within each complex the interest state of each complex in each of a plurality of resource congruence classes, with a complex having an interest in a congruence class if it has previously granted or waited access to a data resource which is a member of the congruence class;

generating within a first complex a first request for access to a resource having a resource key and a resource congruence class;

determining the interest state of said first complex and of a second complex in the resource congruence class of the first access request;

responsive to the determination that the first complex has an interest and the second complex does not have an interest in the resource congruence class of the first access request, processing the first access request within the first complex;

responsive to the second complex having an interest in the resource congruence class of the first access request, communicating the first access request to the second complex for additional processing;

responsive to neither complex having an interest in the resource congruence class of the first access request, communicating the new interest state of the first complex in the resource congruence class of the first access request to the second complex, and processing the first access request within the first complex; and

the processing of the first access request selectively granting, denying, or waiting access to the resource.

2. The method of claim 1 with the processing step comprising the further steps of:

responsive to the determination that either complex has an interest in the congruence class of the first access request, accessing a congruence class file within the complex having the resource keys of all resources within the congruence class previously accessed by the complex and not yet released, and searching for the resource key of the first access request to determine the lock state of the resource to which access is requested;

responsive to the communication of the first access request from the first complex to the second complex, and to the determination that the resource of the first access request has a null lock state in the second complex, communicating a no-interest message to the first complex;

responsive to the determinations that the resource of the first access request has a null lock state in the first complex and that the second complex has no interest in the resource, granting access to the resource and logging the resource key to the congruence class file in the first complex with a held lock state;

responsive to the determination that the resource of the first access request has a held lock state in either or both complexes which is compatible with the first access request, granting access to the resource by logging a held lock state to the congruence class file in the first complex for the resource key; and

responsive to the determination that the resource of the first access request has a held lock state within a complex which is incompatible with the first access request selectively denying access, or waiting access to the resource by logging a wait lock state to the congruence class files in both complexes for the resource key.

3. The method of claim 2, comprising the further steps of:

responsive to release of a held lock state previously logged for a second request for access to the resource of the first request, determining if a wait lock state exists for the resource; and

responsive to the existence of such a wait lock state logged by the first complex, granting access to the resource to the first request by clearing the wait lock state and logging a corresponding held lock state to the congruence class file for the resource key; and

responsive to existence of such a wait lock state logged by the second complex, clearing the wait lock state from the second complex and communicating to the first complex a no-interest message for the resource of the first access request.

4. A method for operating a general purpose computing system to selectively hold and wait locks on shared resources logically organized in congruence classes, the computing system including at least two central electronic complexes interconnected by a communication link and sharing access to the resources, the method comprising the steps of:

maintaining in each complex an interest vector denoting the interest of each complex in each congruence class;

maintaining in each complex, held lock records corresponding to locks held for work units associated with the complex, and wait lock records corresponding to locks waited for work units associated with the complex and selectively for other complexes; and

responsive to a request from work unit for a lock having an access state on a resource of a congruence class, processing the lock request within the one or more complexes determined according to the interest vector.

5. The method of claim 4, wherein locks are organized into groups corresponding to one or more congruence classes, and the lock request processing step further comprises the steps of:

searching the group of locks corresponding to the congruence class of the lock request for a held lock corresponding to the resource of the lock request;

responsive to the finding of a held lock of an access state inconsistent with the request, waiting the lock request;

responsive to the finding of a held lock of an access state consistent with the request, or upon finding no lock corresponding to the resource of the request, adding a held lock to the group of locks maintained only in the complex of the requesting work unit for the congruence class of the request.

6. The method of claim 5, comprising the further steps of:

responsive to release of a lock for a resource for which a lock request is waited on behalf of another complex, releasing the wait lock and communicating to the other complex authorization to grant the lock to the work unit waiting for the lock.

7. The method of claim 4 wherein a complex has an interest in a congruence class if it has granted or waited a lock request on at least one resource of the congruence class to a work unit executing on the complex.

8. Shared resource locking means operable in a multiprocessing/multiprogramming computing environment including at least two central electronic complexes interconnected by a communication link and sharing access to a set of resources organized in at least two congruence classes, comprising:

interest vector means in a first complex for storing the private use and interest of each complex in each congruence class;

means within said first complex responsive to said interest vector means and to a request for a resource in a congruence class in which said first complex has private use for selectively granting or waiting the request based upon the lock records maintained within the first complex; and

means within said first complex responsive to said interest vector means and to a request for a resource in a congruence class in which a second complex has interest for communicating the request to the second complex and selectively granting or waiting the request based upon lock records maintained with the first or second complexes.