Suspension and reinstatement of reference

• US 20050071467A1
• Filed: 10/15/2004
• Published: 03/31/2005
• Est. Priority Date: 06/29/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Douceur, John R., Bernet, Yoram
• Granted Patent: US 7,373,404 B2
• Time in Patent Office: Days
• US Class Current: 709/224
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A handle administration system is described in which software agents receive handles to various resources that they can use to obtain the resources. The described embodiments provide multiple states that can be assumed by the handles. An unassigned state is provided in which handles are not assigned to a particular resource, nor can they be dereferenced to obtain pointers to any resources. An assigned state is provided in which handles are assigned to a particular resource and can be dereferenced to obtain a pointer to the resource. A suspended state is provided in which the handles are assigned to a particular resource but cannot be dereferenced to obtain a pointer to that resource. Advantageously, a suspended handle can be reinstated to assume the assigned state. In one embodiment, the handle system is implemented by incorporating a suitable field in a handle database that is used to indicate that a handle is suspended. In another embodiment, no additional fields are necessary. Rather, handle values in the handle database are manipulated to indicate that a handle has been suspended. These manipulations can be easily undone to reinstate a handle. In the described embodiment, a three state handle system can be advantageously employed to implement a two-phase commit operation.

Claims

1. A method of managing resources comprising:

receiving a handle value;

determining whether the handle value is suspended; and

if the handle value is not suspended, returning a reference pointer that points to a resource with which the handle is associated.

2. The method of claim 1 further comprising determining whether the handle is valid and returning a reference pointer only if the handle is valid and not suspended.

3. The method of claim 2 further comprising returning a null pointer if the handle is invalid or suspended.

4. The method of claim 1 further comprising returning a null pointer if the handle is suspended.

5. The method of claim 1 wherein the handle has more than two states into which it can be placed, the states comprising:

an assigned state in which the handle is associated with a resource and can be dereferenced to obtain a pointer to that resource;

an unassigned state in which the handle is available for assignment to a particular resource; and

a suspended state in which the handle is associated with a particular resource but cannot be dereferenced to obtain a pointer to that resource.

6. The method of claim 5 further comprising reinstating a handle from the suspended state to the assigned state.

7. The method of claim 5 further comprising releasing a handle from the suspended state to the unassigned state.

8. One or more computer-readable media having computer readable instructions thereon which, when executed by one or more computers, cause the computers to:

receive a handle value;

determine whether the handle value is suspended; and

return a reference pointer that points to a resource with which the handle is associated, if the handle is not suspended.

9. The computer-readable media of claim 8, wherein the instructions cause the computers to suspend an assigned handle, the suspended handle being associated with a particular resource but being unable to be dereferenced to obtain a pointer to that resource.

10. A method of managing resources comprising:

defining a handle database that contains information pertaining to a plurality of handles, the information comprising a handle value; and

suspending a handle by adding a value to the handle value.

11. The method of claim 10 further comprising reinstating the suspended handle by subtracting the value from the handle value.

12. The method of claim 10 further comprising releasing the handle.

13. The method of claim 10, wherein said value comprise a handle range step value.

14. The method of claim 10, wherein said value comprises a power of 2.

15. The method of claim 10, wherein the handle database comprises a table having a table size that corresponds to the number of handles that are available for assignment, and wherein the suspending comprises adding a value to the handle value that is larger than the table size.

16. One or more computer-readable media having computer-executable instructions thereon which, when executed by a computer, implement the method of claim 10.

17. A system comprising:

one or more processors;

one or more computer-readable media;

computer-readable instructions on the one or more computer-readable media which, when executed by the one or more processors, cause the one or more processors to implement a method comprising;

receiving a handle value;

determining whether the handle value is suspended; and

if the handle value is not suspended, returning a reference pointer that points to a resource with which the handle is associated.

18. The system of claim 17 further comprising determining whether the handle is valid and returning a reference pointer only if the handle is valid and not suspended.

19. The system of claim 18 further comprising returning a null pointer if the handle is invalid or suspended.

20. The system of claim 17 further comprising returning a null pointer if the handle is suspended.

21. The system of claim 17 wherein the handle has more than two states into which it can be placed, the states comprising:

an assigned state in which the handle is associated with a resource and can be dereferenced to obtain a pointer to that resource;

an unassigned state in which the handle is available for assignment to a particular resource; and

a suspended state in which the handle is associated with a particular resource but cannot be dereferenced to obtain a pointer to that resource.

22. The system of claim 21 further comprising reinstating a handle from the suspended state to the assigned state.

23. The system of claim 21 further comprising releasing a handle from the suspended state to the unassigned state.

24. A system comprising:

means for receiving a handle value;

means for determining whether the handle value is suspended; and

means for, if the handle value is not suspended, returning a reference pointer that points to a resource with which the handle is associated.

25. The system of claim 24 further comprising means for determining whether the handle is valid and means for returning a reference pointer only if the handle is valid and not suspended.

26. The system of claim 25 further comprising means for returning a null pointer if the handle is invalid or suspended.

27. The system of claim 24 further comprising means for returning a null pointer if the handle is suspended.

28. The system of claim 24 wherein the handle has more than two states into which it can be placed, the states comprising:

an assigned state in which the handle is associated with a resource and can be dereferenced to obtain a pointer to that resource;

an unassigned state in which the handle is available for assignment to a particular resource; and

a suspended state in which the handle is associated with a particular resource but cannot be dereferenced to obtain a pointer to that resource.

29. The system of claim 28 further comprising means for reinstating a handle from the suspended state to the assigned state.

30. The system of claim 28 further comprising means for releasing a handle from the suspended state to the unassigned state.

31. A system comprising:

one or more processors;

one or more computer-readable media;

computer-readable instructions on the one or more computer-readable media which, when executed by the one or more processors, cause the one or more processors to implement a method comprising;

defining a handle database that contains information pertaining to a plurality of handles, the information comprising a handle value; and

suspending a handle by adding a value to the handle value.

32. The system of claim 31 further comprising reinstating the suspended handle by subtracting the value from the handle value.

33. The system of claim 31 further comprising releasing the handle.

34. The system of claim 31, wherein said value comprise a handle range step value.

35. The system of claim 31, wherein said value comprises a power of 2.

36. The system of claim 31, wherein the handle database comprises a table having a table size that corresponds to the number of handles that are available for assignment, and wherein the suspending comprises adding a value to the handle value that is larger than the table size.