Locking Access To Data Storage Shared By A Plurality Of Compute Nodes

• US 20120144138A1
• Filed: 12/02/2010
• Published: 06/07/2012
• Est. Priority Date: 12/02/2010
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kandasamy, Madhusudanan, Ranganathan, Vidya, Vaddagiri, Murali
• Granted Patent: US 8,949,566 B2
• Time in Patent Office: Days
• US Class Current: 711/163
• CPC Class Codes: G06F 16/1774 Locking methods, e.g. locking methods for file systems allowing shared and concurrent access to files
• CPC Class Codes: G06F 8/458 Synchronisation, e.g. post-wait, barriers, locks synchronisation among tasks G06F9/52
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: G06F 9/524 Deadlock detection or avoidance
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms
• CPC Class Codes: G06F 9/546 Message passing systems or structures, e.g. queues

Abstract

Methods, apparatuses, and computer program products are provided for locking access to data storage shared by a plurality of compute nodes. Embodiments include maintaining, by a compute node, a queue of requests from requesting compute nodes of the plurality of compute nodes for access to the data storage, wherein possession of the queue represents possession of a mutual-exclusion lock on the data storage, the mutual-exclusion lock indicating exclusive permission for access to the data storage; and conveying, based on the order of requests in the queue, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage.

Claims

1. A method for locking access to data storage shared by a plurality of compute nodes, the method comprising:

maintaining, by a compute node, a queue of requests from requesting compute nodes of the plurality of compute nodes for access to the data storage, wherein possession of the queue represents possession of a mutual-exclusion lock on the data storage, the mutual-exclusion lock indicating exclusive permission for access to the data storage; and

conveying, based on the order of requests in the queue, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage.

2. The method of claim 1, further comprising:

receiving, by the compute node from a requesting compute node, a request for access to the data storage;

in response to receiving the request for access to the data storage, transmitting, by the compute node, an acknowledgment indicating that the compute node has the mutual-exclusion lock on the data storage.

3. The method of claim 2, wherein the requesting compute node transmits the request for access to the plurality of compute nodes and only the compute node with the mutual-exclusion lock transmits the acknowledgment to the requesting compute node.

4. The method of claim 1, further comprising:

determining, by a requesting compute node, whether access to the data storage is locked by examining a lock status table that is stored in memory that is accessible by each of the nodes;

in response to determining that the data storage is not locked, acquiring, by the requesting compute node, the mutual-exclusion lock on the data storage by updating the lock status table to indicate that access to the data storage is locked; and

in response to determining that the data storage is locked, transmitting from the requesting compute node to the plurality of compute nodes, a request for access to the data storage.

5. The method of claim 4, further comprising in response to receiving the queue, updating, by the next requesting compute node, the lock status table to indicate that access to the data storage is locked.

6. The method of claim 1, further comprising:

determining, by a requesting compute node, whether an acknowledgement is received within a predetermined amount of time after transmitting a request for access to the data storage; and

if an acknowledgment is not received within the predetermined amount of time, acquiring, by the requesting compute node, the mutual-exclusion lock on the data storage.

7. The method of claim 1, wherein the request queue is stored at the compute node that has the mutual-exclusion lock on the data storage.

8. The method of claim 1, wherein conveying, based on the order of requests in the queue, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage is further based on a priority of the plurality of compute nodes;

wherein conveying, based on the order of requests in the queue and the priority of the plurality of compute nodes, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage includes in response to the compute node receiving at the same time, a first request for access to the queue from a first requesting compute node and a second request for access from a second requesting compute node, conveying the queue to the first requesting compute node when the priority of the first requesting compute node is higher than the priority of the second requesting compute node.

9. The method of claim 1, wherein conveying possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage includes:

transmitting the queue to the next requesting compute node;

receiving a queue transfer acknowledgement from the next requesting compute node; and

transmitting a new request acknowledgement that indicates any new requests that are received by the compute node after the compute node transmits the queue to the next requesting compute node.

10. An apparatus for prioritizing control of access to data storage, the apparatus comprising a plurality of compute nodes, each compute node comprising a computer processor and a computer readable memory operatively coupled to the computer processor, the computer readable memory having disposed within it computer program instructions that when executed by the computer processor, cause the apparatus to carry out the steps of:

maintaining, by a compute node, a queue of requests from requesting compute nodes of the plurality of compute nodes for access to the data storage, wherein possession of the queue represents possession of a mutual-exclusion lock on the data storage, the mutual-exclusion lock indicating exclusive permission for access to the data storage; and

conveying, by the compute node, based on the order of requests in the queue, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage.

11. The apparatus of claim 10, further comprising computer program instructions that when executed by the computer processor, cause the apparatus to carry out the steps of:

receiving, by the compute node from a requesting compute node, a request for access to the data storage;

in response to receiving the request for access to the data storage, transmitting, by the compute node, an acknowledgment indicating that the compute node has the mutual-exclusion lock on the data storage.

12. The apparatus of claim 11, wherein the requesting compute node transmits the request for access to the plurality of compute nodes and only the compute node with the mutual-exclusion lock transmits the acknowledgment to the requesting compute node.

13. The apparatus of claim 10, further comprising computer program instructions that when executed by the computer processor, cause the apparatus to carry out the steps of:

determining, by a requesting compute node, whether access to the data storage is locked by examining a lock status table that is stored in memory that is accessible by each of the nodes;

in response to determining that the data storage is not locked, acquiring, by the requesting compute node, the mutual-exclusion lock on the data storage by updating the lock status table to indicate that access to the data storage is locked; and

in response to determining that the data storage is locked, transmitting from the requesting compute node to the plurality of compute nodes, a request for access to the data storage.

14. The apparatus of claim 13, further comprising computer program instructions that when executed by the computer processor, cause the apparatus to carry out the steps of in response to receiving the queue, updating, by the next requesting compute node, the lock status table to indicate that access to the data storage is locked.

15. The apparatus of claim 10, further comprising computer program instructions that when executed by the computer processor, cause the apparatus to carry out the steps of:

determining, by a requesting compute node, whether an acknowledgement is received within a predetermined amount of time after transmitting a request for access to the data storage; and

if an acknowledgment is not received within the predetermined amount of time, acquiring, by the requesting compute node, the mutual-exclusion lock on the data storage.

16. A computer program product for locking access to data storage shared by a plurality of compute nodes, the computer program product comprising:

a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising computer readable program code configured to;

maintain, by a compute node, a queue of requests from requesting compute nodes of the plurality of compute nodes for access to the data storage, wherein possession of the queue represents possession of a mutual-exclusion lock on the data storage, the mutual-exclusion lock indicating exclusive permission for access to the data storage; and

convey, based on the order of requests in the queue, possession of the queue from the compute node to a next requesting compute node when the compute node no longer requires exclusive access to the data storage.

17. The computer program product of claim 16, further comprising computer program code configured to:

receive, by the compute node from a requesting compute node, a request for access to the data storage;

in response to receiving the request for access to the data storage, transmit, by the compute node, an acknowledgment indicating that the compute node has the mutual-exclusion lock on the data storage.

18. The computer program product of claim 17, wherein the requesting compute node transmits the request for access to the plurality of compute nodes and only the compute node with the mutual-exclusion lock transmits the acknowledgment to the requesting compute node.

19. The computer program product of claim 16, further comprising computer program code configured to:

determine, by a requesting compute node, whether access to the data storage is locked by examining a lock status table that is stored in memory that is accessible by each of the nodes;

in response to determining that the data storage is not locked, acquire, by the requesting compute node, the mutual-exclusion lock on the data storage by updating the lock status table to indicate that access to the data storage is locked; and

in response to determining that the data storage is locked, transmit from the requesting compute node to the plurality of compute nodes, a request for access to the data storage.

20. The computer program product of claim 19, further comprising computer program code configured to in response to receiving the queue, update, by the next requesting compute node, the lock status table to indicate that access to the data storage is locked.