Lock holding multi-threaded processes for distibuted data systems

• US 20040019660A1
• Filed: 07/24/2002
• Published: 01/29/2004
• Est. Priority Date: 07/24/2002
• Status: Abandoned Application

• Current Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: E., Sandhya, Kumar, Ajay
• Application Number:
  US10/201,846
• Publication Number:
  US 20040019660A1
• Time in Patent Office: Days
• US Class Current: 709/219
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A distributed data system may include nodes each including a process that may access distributed data. A lock mechanism coupled to the distributed data store may grant locks for portions of the distributed data. Only threads of a process holding a lock for a portion of the distributed data may access the portion. A process may obtain a lock for a distributed data portion. In one embodiment, the process may release the lock if no more threads require access to the portion so may initiate a “dummy” thread requester indicating a thread requiring access to the portion. If other threads requiring access are initiated, it may not be necessary to obtain the lock again. This may help reduce the use of resources associated with using locks. If the process receives a request to release the lock, the process may cancel the dummy thread requester and release the lock.

Claims

1. A distributed data system comprising:

a plurality of network nodes each configured to execute one or more processes;

a data store configured to store primary data accessible by the processes; and

a lock mechanism coupled to the data store and configured to lock access to portions of the primary data, wherein the lock mechanism is configured to grant a lock to a requester for one of the processes for a primary data portion stored by the data store, wherein the lock mechanism is configured to prevent other processes from accessing the primary data portion while the requester is granted the lock;

wherein each of the processes comprises one or more threads each configured to request a lock for a portion of the primary data for its process, wherein the process is configured to hold the lock as long as one of the threads of the process requests access to the locked portion of the primary data, wherein the process is configured to maintain a dummy request for the locked portion of the primary data so that the lock is held for the process until the process is requested to release the lock.

2. The distributed data system as recited in claim 1, wherein each of the processes is configured to cancel the dummy request in response to a request to release the lock.

3. The distributed data system as recited in claim 1, wherein the dummy request is asserted by a dummy request thread of each respective process.

4. The distributed data system as recited in claim 3, wherein the dummy request to access the locked portion of primary data remains pending so that the process retains the lock when no other threads of the same process are requesting access to the locked portion of the primary data, so that another thread of the same process subsequently requesting access to the locked portion of primary data is not required to obtain the lock for the locked portion of primary data.

5. The distributed data system as recited in claim 3, wherein each of the processes is configured to cancel the dummy request and terminate the execution of the dummy request thread in response to a request to release the lock.

6. The distributed data system as recited in claim 1, wherein each of the processes is configured so that if the process acquires the lock, one or more other threads of the process requesting access to the portion of the primary data access the portion of the primary data while the process retains the lock.

7. The distributed data system as recited in claim 6, wherein each of the processes is configured to:

increment a count in response to a thread of the process requesting access to the locked portion of the primary data; and

decrement the count in response to a thread of the process completing access to the locked portion of the primary data.

8. The distributed data system as recited in claim 7, wherein each of the processes is configured to:

increment the count in response to the dummy request; and

in response to a request to release the lock, cancel the dummy request and decrement the count; and

release the lock in response to the count reaching an initial value.

9. The distributed data system as recited in claim 1, wherein each of the processes comprises a thread configured to request release of the lock.

10. The distributed data system as recited in claim 1, wherein the lock mechanism is configured to allow only the requester for a lock to release the lock for the corresponding portion of the primary data.

11. The distributed data system as recited in claim 1, wherein the plurality of network nodes comprise one or more application servers of a multi-tiered enterprise system.

12. The distributed data system as recited in claim 1, wherein the one of the processes comprises a Java virtual machine.

13. The distributed data system as recited in claim 1, wherein a portion of the primary data stored by the data store represents state information of a client-server session.

14. The distributed data system as recited in claim 1, wherein if a requester for a process holds a lock for a portion of the primary data, the lock mechanism is configured to buffer one or more requests for the lock for that portion of the primary from one or more other requesters for one or more other processes.

15. The distributed data system as recited in claim 14, wherein in response to the requester releasing the lock for the portion of the primary data, the lock mechanism is configured to grant the lock for that portion of the primary data to a next buffered requester for that primary data portion.

16. A computing system comprising:

a processor;

memory comprising program instructions executable by the processor to implement;

a process configured to access portions of distributed data stored within a data store accessible to other processes;

wherein the process comprises one or more threads each configured to request a lock for one of the portions of distributed data on behalf of the process from a lock mechanism of the data store, wherein the process is configured to hold the lock as long as one of the threads of the process requests access to the locked portion of the distributed data, wherein the process is configured to maintain a dummy request for the locked portion of the distributed data so that the lock is held for the process until the process is requested to release the lock.

17. The computing system as recited in claim 16, wherein the process is configured to cancel the dummy request in response to a request to release the lock.

18. The computing system as recited in claim 16, wherein the dummy request is asserted by a dummy request thread of the process.

19. The computing system as recited in claim 18, wherein the dummy request to access the locked portion of primary data remains pending so that the process retains the lock when no other threads of the process are requesting access to the locked portion of the primary data, so that another thread of the process subsequently requesting access to the locked portion of the distributed data is not required to obtain the lock for the locked portion of the distributed data.

20. The computing system as recited in claim 18, wherein the process is configured to cancel the dummy request and terminate execution of the dummy request thread in response to a request to release the lock.

21. The computing system as recited in claim 16, wherein the process is configured so that if the process acquires the lock, one or more other threads of the process requesting access to the portion of the distributed data access the portion of the distributed data while the process retains the lock.

22. The computing system as recited in claim 21, wherein the process is configured to:

increment a count in response to a thread of the process requesting access to the locked portion of the distributed data; and

decrement the count in response to a thread of the process completing access to the locked portion of the distributed data.

23. The computing system as recited in claim 22, wherein the process is configured to:

increment the count in response to the dummy request; and

in response to a request to release the lock, cancel the dummy request and decrement the count; and

release the lock in response to the count reaching an initial value.

24. The computing system as recited in claim 16, wherein the process comprises a thread configured to request release of the lock.

25. The computing system as recited in claim 16, wherein the process comprises a Java virtual machine.

26. A method comprising:

a thread of a process requesting a lock on behalf of the process for a portion of primary data stored within a data store from a lock mechanism of a data store;

if the thread is granted the lock, the process holding the lock as long as one of the threads of the process requests access to the locked portion of the primary data; and

the process maintaining a dummy request for the locked portion of the primary data so that the lock is continued to be held for the process until the process is requested to release the lock.

27. The method as recited in claim 26, further comprising the process canceling the dummy request in response to a request to release the lock.

28. The method as recited in claim 26, further comprising a dummy request thread of the process asserting the dummy request.

29. The method as recited in claim 28, further comprising the dummy request to access the locked portion of primary data remaining pending so that the process retains the lock when no other threads of the process are requesting access to the locked portion of the primary data, so that another thread of the process subsequently requesting access to the locked portion of the primary data is not required to obtain the lock for the locked portion of the primary data.

30. The method as recited in claim 28, further comprising the process canceling the dummy request and terminating execution of the dummy request thread in response to a request to release the lock.

31. The method as recited in claim 26, further comprising, if the thread is granted the lock, the process providing access to the portion of the primary data to one or more other threads of the process requesting access to the portion of the primary data while the process retains the lock.

32. The method as recited in claim 31, further comprising:

the process incrementing a count in response to a thread of the process requesting access to the locked portion of the primary data; and

the process decrementing the count in response to a thread of the process completing access to the locked portion of the primary data.

33. The method as recited in claim 32, further comprising:

the process incrementing the count in response to the dummy request;

in response to a request to release the lock, the process canceling the dummy request and decrementing the count; and

the process releasing the lock in response to the count reaching an initial value.

34. The method as recited in claim 26, further comprising another thread of the process requesting release of the lock.

35. An article of manufacture comprising program instructions executable to implement:

a thread of a process requesting a lock on behalf of the process for a portion of primary data stored within a data store from a lock mechanism of a data store;

if the thread is granted the lock, the process holding the lock as long as one of the threads of the process requests access to the locked portion of the primary data; and

the process maintaining a dummy request for the locked portion of the primary data so that the lock is continued to be held for the process until the process is requested to release the lock.

36. The article of manufacture as recited in claim 35, wherein the program instructions are further executable to implement the process canceling the dummy request in response to a request to release the lock.

37. The article of manufacture as recited in claim 35, wherein the program instructions are further executable to implement a dummy request thread of the process asserting the dummy request.

38. The article of manufacture as recited in claim 37, wherein the program instructions are further executable to implement the dummy request to access the locked portion of primary data remaining pending so that the process retains the lock when no other threads of the process are requesting access to the locked portion of the primary data, so that another thread of the process subsequently requesting access to the locked portion of the primary data is not required to obtain the lock for the locked portion of the primary data.

39. The article of manufacture as recited in claim 37, wherein the program instructions are further executable to implement the process canceling the dummy request and terminating execution of the dummy request thread in response to a request to release the lock.

40. The article of manufacture as recited in claim 35, wherein the program instructions are further executable to implement, if the thread is granted the lock, the process providing access to the portion of the primary data to one or more other threads of the process requesting access to the portion of the primary data while the process retains the lock.

41. The article of manufacture as recited in claim 40, wherein the program instructions are further executable to implement:

the process incrementing a count in response to a thread of the process requesting access to the locked portion of the primary data; and

the process decrementing the count in response to a thread of the process completing access to the locked portion of the primary data.

42. The article of manufacture as recited in claim 41, wherein the program instructions are further executable to implement:

the process incrementing the count in response to the dummy request;

in response to a request to release the lock, the process canceling the dummy request and decrementing the count; and

the process releasing the lock in response to the count reaching an initial value.

43. The article of manufacture as recited in claim 35, wherein the program instructions are further executable to implement another thread of the process requesting release of the lock.