Systems and methods for managing semantic locks

• US 8,082,379 B2
• Filed: 03/23/2009
• Issued: 12/20/2011
• Est. Priority Date: 01/05/2007
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Fachan, Neal T., Passey, Aaron J.
• Primary Examiner(s): Auve, Glenn A
• Application Number:
  US12/409,377
• Publication Number:
  US 20090210880A1
• Time in Patent Office: 1,002 Days
• Field of Search: 707/704, 707/781, 710/200, 718/100, 718/107, 718/108
• US Class Current: 710/200
• CPC Class Codes: G06F 2209/523 Mode
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

In one embodiment, a system for managing semantic locks and semantic lock requests for a resource is provided. Access to the resource is controlled such that compatible lock requests can access the resource and incompatible lock requests are queued.

Claims

1. A system for managing semantic locks and semantic lock requests for a resource, the system comprising:

a resource;

a resource lock information indicating existing locks on said resource;

a first lock compatibility table stored in a memory including information on a plurality of lock types, said information relating to the compatibility among the plurality of lock types; and

a software module configured to;

receive a first lock request;

access said first lock compatibility table and said resource lock information to determine whether said first lock request is compatible with existing locks on said resource; and

transmit a response indicating that said first lock request could be granted if said first lock request is compatible with the existing locks on said resource,

wherein said first lock request comprises priority information indicating whether said first lock request should be processed by said software module before a second pending lock request or after said second pending lock request.

2. The system of claim 1, wherein said software module is further configured to transmit the response indicating that said first lock request could be granted if said first lock request is compatible with a second pending lock request.

3. The system of claim 1, wherein said software module is associated with a second node, said second node assigned to said resource.

4. The system of claim 3, wherein said first lock request originates from a first node remote from said second node.

5. The system of claim 4, wherein said second node is configured to grant or deny said first lock request.

6. The system of claim 3, wherein said second node tracks said resource lock information.

7. The system of claim 1, wherein said resource lock information includes:

the types of locks on said resource; and

the types of locks that a third node should have on the resource in order to accommodate said first lock request.

8. The system of claim 1, wherein said first lock compatibility table disallows equal lock types.

9. The system of claim 1, wherein said first lock compatibility table is asymmetric.

10. The system of claim 1, wherein said priority information indicates that said first lock request should be processed before said second pending lock request if said first lock request comprises a recursive lock request.

11. The system of claim 1, wherein said priority information indicates that said first lock request should be processed before said second pending lock request if said first lock request comprises a conversion of an existing lock on said resource.

12. The system of claim 1, wherein said software module is configured to determine, with at least said priority information, whether to place said first lock request at a front or at a back of a queue for pending lock requests.

13. The system of claim 1, wherein said resource lock information comprises a representation of a number of owners of at least one type of existing lock on said resource, and said software module is configured to determine whether said first lock request is compatible with said existing locks on said resource using at least said representation.

14. The system of claim 13, wherein said representation comprises said number of owners of each type of existing lock on said resource.

15. The system of claim 13, wherein said resource lock information further comprises a representation of a number of pending lock requests for at least one type of lock on said resource.

16. The system of claim 13, wherein said representation comprises a first data if said number of owners is zero, a second data if said number of owners is one, or a third data if said number of owners is greater than one.

17. The system of claim 16, wherein said software module is configured to determine that said first lock request is compatible with said existing locks on said resource if said representation comprises said first data.

18. The system of claim 16, wherein said second data indicates said one owner that owns said existing lock on said resource.

19. The system of claim 18, wherein said second data comprises a device identifier of said one owner.

20. The system of claim 18, wherein said software module is configured to determine that said first lock request is compatible with said existing locks on said resource if said representation comprises said second data and said owner that transmitted said first lock request is said one owner.

21. The system of claim 1, wherein said resource lock information comprises a count information indicating a number of existing locks for each of said plurality of lock types, and said software module is configured to receive a lock release request, said lock release request comprising a release information indicating, for at least one type of existing lock, a number of existing locks that should be released.

22. The system of claim 21, wherein said software module is further configured to update said count information using at least said release information.

23. The system of claim 22, wherein said software module is further configured to transmit said response indicating that said first lock request could be granted if said count information indicates said number of existing locks is zero.

24. A method for managing semantic locks and semantic lock requests for a resource, the method comprising:

receiving a first lock request for a resource;

accessing a first lock compatibility table and a resource lock information to determine whether said first lock request is compatible with existing locks on said resource, wherein;

the first lock compatibility table stores information relating to the compatibility among a plurality of lock types; and

the resource lock information indicates existing locks on said resource; and

transmitting a response indicating that said first lock request could be granted if said first lock request is compatible with the existing locks on said resource,

wherein said first lock request comprises priority information indicating whether said first lock request should be processed before a second pending lock request or after said second pending lock request.

25. The method of claim 24, wherein the response is transmitted if said first lock request is compatible with a second pending lock request.

26. The method of claim 24, wherein the first lock request is received at a second node, said second node assigned to said resource.

27. The method of claim 26, wherein said first lock request originates from a first node remote from said second node.

28. The method of claim 27, wherein said second node tracks said resource lock information.

29. The method of claim 27, wherein said second node is configured to grant or deny said first lock request.

30. The method of claim 24, wherein said resource lock information includes:

the types of locks on said resource; and

the types of locks that a third node should have on the resource in order to accommodate said first lock request.

31. The method of claim 24, wherein said first lock compatibility table disallows equal lock types.

32. The method of claim 24, wherein said lock compatibility table is asymmetric.

33. The method of claim 24, wherein said priority information indicates that said first lock request should be processed before said second pending lock request if said first lock request comprises a recursive lock request.

34. The method of claim 24, wherein said priority information indicates that said first lock request should be processed before said second pending lock request if said first lock request comprises a conversion of an existing lock on said resource.

35. The method of claim 24, further comprising determining, with at least said priority information, whether to place said first lock request at a front or at a back of a queue for pending lock requests.

36. The method of claim 24, wherein said resource lock information comprises a representation of a number of owners of at least one type of existing lock on said resource, and said accessing further comprises determining whether said first lock request is compatible with said existing locks on said resource using at least said representation.

37. The method of claim 36, wherein said representation comprises said number of owners of each type of existing lock on said resource.

38. The method of claim 36, wherein said resource lock information further comprises a representation of a number of pending lock requests for at least one type of lock on said resource.

39. The method of claim 36, wherein said representation comprises a first data if said number of owners is zero, a second data if said number of owners is one, or a third data if said number of owners is greater than one.

40. The method of claim 39, wherein determining whether said first lock request is compatible with said existing locks on said resource using at least said representation comprises determining whether said representation comprises said first data.

41. The method of claim 39, wherein said second data indicates said one owner that owns said existing lock on said resource.

42. The method of claim 41, wherein said second data comprises a device identifier of said one owner.

43. The method of claim 41, wherein determining whether said first lock request is compatible with said existing locks on said resource using at least said representation comprises determining whether said representation comprises said second data and said owner that transmitted said first lock request is said one owner.

44. The method of claim 24, further comprising:

receiving a lock release request, said lock release request comprising release information indicating, for at least one type of existing lock, a number of locks that should be released,

wherein said resource lock information comprises a count information indicating a number of existing locks for each of said plurality of lock types.

45. The method of claim 44, further comprising updating said count information using at least said release information.

46. The method of claim 45, wherein transmitting a response indicating that said first lock request could be granted further comprises transmitting said response if said count information indicates said number of existing locks is zero.