System and method for handling resource transaction requests

• US 20030145146A1
• Filed: 01/18/2003
• Published: 07/31/2003
• Est. Priority Date: 01/25/2002
• Status: Active Grant

• Current Assignee: X Corp. (f/k/a Twitter, Inc.) (X Holdings Corp.)
• Original Assignee: International Business Machines Corporation
• Inventors: Flasza, Miroslaw A., Huras, Matthew A., Winer, Michael J., Zheng, Roger L.Q., Goss, Jeffrey J., McArthur, Catherine S., Meadowcroft, Lorysa M., Posner, Sarah
• Granted Patent: US 7,069,366 B2
• Time in Patent Office: Days
• US Class Current: 710/200
• CPC Class Codes: G06F 16/24557 Efficient disk access during query execution
• CPC Class Codes: G06F 2209/522 Manager
• CPC Class Codes: G06F 2209/523 Mode
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

A system and method handle resource transaction requests. The system marks a waiting transaction request, having an access mode which is incompatible with the access mode of the executing transaction, with an ignore bit, so that a transaction request with an access mode compatible with the access mode of the executing transaction may receive a lock in order to access the resource. The transaction request is then marked with a bypass indicator such that when the executing transactions are finished accessing the resource, the waiting transaction request may be notified that it may have access to the resource. The system includes the ignore bit so that each transaction request that arrives after the ignore bit has been set, does not suffer from a long waiting time before being provided access to the resource

Claims

1. A method of handling a lock request from a requesting transaction request for access to a resource executing at least one prior transaction request, comprising:

receiving a lock request from the requesting transaction request;

determining if a conflict exists between an access mode of the requesting transaction request and an access mode of the prior transaction request;

wherein if the conflict exists, determining if the prior transaction request has been refused and is currently waiting for access to the resource;

wherein if the prior transaction request is not waiting for access to the resource, assigning an ignore indicator to the requesting transaction request; and

wherein the ignore indicator allows a subsequent transaction request to be granted access to the resource if an access mode of the subsequent transaction request does not conflict with the access mode of the prior transaction request.

2. The method of claim 1, further comprising setting an overall ignore bit if the ignore indicator is assigned to the requesting transaction request.

3. The method of claim 1, further comprising:

if the prior transaction request is waiting for access to the resource, setting a lock status of the requesting transaction request to a waiting status; and

assigning a bypass indicator to the requesting transaction request.

4. The method of claim 1, further comprising granting a bypass indicator to the subsequent transaction request.

5. The method of claim 4, further comprising:

monitoring the prior transaction request to determine when the prior transaction request has been assigned the bypass indicator; and

granting the requesting transaction request access to the resource.

6. The method of claim 5, further comprising clearing the bypass indicator and the ignore indicator.

7. An apparatus for handling a lock request from a requesting transaction request for access to a resource executing at least one prior transaction request comprising:

a lock manager that receives the lock request from the requesting transaction request, and that compares an access mode of the requesting transaction request with an access mode of the prior transaction request; and

a requester that assigns an ignore indicator to the requesting transaction request if a conflict exists between the access mode of the requesting transaction request and the access mode of the prior transaction request;

wherein if the prior transaction request is not waiting for access to the resource, the requester further assigns an ignore indicator to the requesting transaction request; and

wherein the ignore indicator allows a subsequent transaction request to be granted access to the resource if an access mode of the subsequent transaction request does not conflict with the access mode of the prior transaction request.

8. The apparatus of claim 7, wherein the requester further sets an overall ignore indicator if the ignore indicator is granted.

9. The apparatus of claim 8, wherein the lock manager assigns a bypass indicator to the subsequent transaction request.

10. The apparatus of claim 9, wherein when the prior transaction request is assigned the bypass indicator, the lock manager grants access to the resource for the requesting transaction request.

11. A computer program product having instruction codes for handling a lock request from a requesting transaction request for access to a resource executing at least one prior transaction request, comprising:

a first set of instruction codes for receiving a lock request from the requesting transaction request;

a second set of instruction codes for determining if a conflict exists between an access mode of the requesting transaction request and an access mode of the prior transaction request;

wherein if the conflict exists, the second set of instruction codes determines if the prior transaction request has been refused and is currently waiting for access to the resource;

wherein if the prior transaction request is not waiting for access to the resource, the second set of instruction codes assigns an ignore indicator to the requesting transaction request; and

wherein the ignore indicator allows a subsequent transaction request to be granted access to the resource if an access mode of the subsequent transaction request does not conflict with the access mode of the prior transaction request.

12. The computer program product of claim 11, further comprising a third set of instruction codes for setting an overall ignore bit if the ignore indicator is assigned to the requesting transaction request.

13. The computer program product of claim 11, wherein if the prior transaction request is waiting for access to the resource, the third set of instruction codes sets a lock status of the requesting transaction request to a waiting status, and further assigns a bypass indicator to the requesting transaction request.

14. The computer program product of claim 11, further comprising a third set of instruction codes for granting a bypass indicator to the subsequent transaction request.

15. The computer program product of claim 14, further comprising a fourth set of instruction codes for monitoring the prior transaction request to determine when the prior transaction request has been assigned the bypass indicator and for granting the requesting transaction request access to the resource.

16. The computer program product of claim 15, further comprising a fifth set of instruction codes for clearing the bypass indicator and the ignore indicator.

17. A system for handling a lock request from a requesting transaction request for access to a resource executing at least one prior transaction request, comprising:

means for receiving a lock request from the requesting transaction request;

means for determining if a conflict exists between an access mode of the requesting transaction request and an access mode of the prior transaction request;

means for determining if the prior transaction request has been refused and is currently waiting for access to the resource, if a conflict is determined to exist,;

means for assigning an ignore indicator to the requesting transaction request, if the prior transaction request is not waiting for access to the resource; and

wherein the ignore indicator allows a subsequent transaction request to be granted access to the resource if an access mode of the subsequent transaction request does not conflict with the access mode of the prior transaction request.

18. The system of claim 17, further comprising means for setting an overall ignore bit if the ignore indicator is assigned to the requesting transaction request.

19. The system of claim 17, wherein if the prior transaction request is waiting for access to the resource, the setting means sets a lock status of the requesting transaction request to a waiting status, and further assigns a bypass indicator to the requesting transaction request.

20. The system of claim 17, further comprising means for granting a bypass indicator to the subsequent transaction request.

21. The system of claim 20, further comprising means for monitoring the prior transaction request to determine when the prior transaction request has been assigned the bypass indicator and for granting the requesting transaction request access to the resource.

22. The system of claim 21, further comprising means for clearing the bypass indicator and the ignore indicator.

23. A method of handling a lock request from a requesting transaction request for access to a resource executing at least one prior transaction request, comprising:

receiving a lock request from the requesting transaction request;

determining if a conflict exists between an access mode of the requesting transaction request and an access mode of the prior transaction request;

wherein if the conflict exists, assigning an ignore indicator to the requesting transaction request; and

wherein the ignore indicator allows a subsequent transaction request to be granted access to the resource if an access mode of the subsequent transaction request does not conflict with the access mode of the prior transaction request.