Using Local Locks For Global Synchronization In Multi-Node Systems

• US 20080059471A1
• Filed: 11/06/2007
• Published: 03/06/2008
• Est. Priority Date: 05/09/2003
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Chandrasekaran, Sashikanth, Loaiza, Juan, MacNaughton, Neil
• Granted Patent: US 8,224,977 B2
• Time in Patent Office: Days
• US Class Current: 707/8
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Described herein are techniques for global synchronization that under various scenarios eliminate or defer the acquisition of global locks. In many cases, the need to acquire global locks is eliminated, thereby saving the overhead attendant to processing global locks.

Claims

1. A method for managing locks granted by a multi-node system to access a set of shared resources that includes a first shared resource, the method comprising the steps of:

granting a first local lock on the first shared resource to a first node;

based on the first local lock, permitting the first node to access the first shared resource; and

while said first node holds said first local lock, and in response to a request from a second node for a global lock on the first shared resource, causing said first node to obtain a global lock on the first shared resource.

2. The method of claim 1, wherein:

the method further includes receiving a request from the first node for a lock on the first shared resource that allows the first node to access the first shared resource;

the method further includes determining, based on one or more conditions, whether the request from the first node may be honored by granting only a local lock; and

the step of permitting the first node to access the first shared resource is performed only if the request from the first node may be honored by granting only a local lock.

3. The method of claim 2, wherein the one or more conditions include that the first shared resource is not globally locked by another node.

4. The method of claim 2, wherein the one or more conditions include that the first shared resource is mastered by another node other than the first node.

5. The method of claim 1, wherein the first shared resource is mastered by the first node.

6. The method of claim 1, the method further including permitting processes on the first node to access the first shared resource based on a local lock granted by the first node to each of the other processes.

7. The method of claim 1, wherein the step of granting a first local lock is performed in response to the first node creating the first shared resource.

8. The method of claim 7, wherein the first shared resource is mastered by another node other than the first node.

9. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1.

10. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 2.

11. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 3.

12. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 4.

13. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 5.

14. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 6.

15. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 7.

16. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 8.

17. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 9.

18. A computer-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 10.