Agent-implemented locking mechanism

• US 5,913,227 A
• Filed: 03/24/1997
• Issued: 06/15/1999
• Est. Priority Date: 03/24/1997
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Johnson, Douglas V., Caritj, Walter Michael, Raz, Yoav
• Primary Examiner(s): Cabeca, John W.
• Assistant Examiner(s): GOODARZI, NASSER MOAZZAMI
• Application Number:
  US08/822,680
• Time in Patent Office: 813 Days
• Field of Search: 711/152, 711/151, 711/211, 711/149, 395/280, 395/561, 395/726, 395/290, 395/860
• US Class Current: 711/152
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A method of synchronizing access to a data object that is stored within a shared storage area of a data storage system to which a plurality of host processors are connected, the method including the steps of establishing one of the plurality of host processors as a master host processor, wherein the master host processor owns the shared object within the data storage system; sending an access request from a slave host processor to the master host processor to access the shared object within the data storage system, wherein the slave host processor is one of the plurality of host processors other than the master host processor; in response to receiving the access request at the master host processor, checking whether any conflicting locks are still pending from prior access requests from any of the plurality of host processors; if no locks are still pending, granting the access request from the slave host processor; and notifying the slave processor whether its access request was granted.

Claims

1. A method of synchronizing access to an identified data object that is stored within a shared storage area of a data storage system to which a plurality of processors are connected, each of said plurality of processors being connected to said data storage system through a corresponding different channel, said method comprising:

establishing one of said plurality of processors as a master processor, wherein said master processor owns the identified shared object within the data storage system;

sending an access request from a slave processor to the master processor to access the identified shared object within the data storage system, said slave processor being one of said plurality of processors other than the master processor;

in response to receiving the access request at the master processor, checking whether any conflicting locks are still pending from prior access requests from any of the plurality of processors;

if no locks are still pending, granting the access request from the slave processor; and

notifying the slave processor whether its access request was granted.

2. The method of claim 1 further comprising the step of denying the access request from the slave processor if a conflicting lock is still pending and wherein notifying step includes notifying the slave processor whether its access request was granted or denied.

3. The method of claim 2 wherein the step of granting an access request comprises recording in local memory that the access request was granted to the requesting processor.

4. The method of claim 3 wherein the object is a file system.

5. The method of claim 4 wherein the access request is a request to access a file in the file system.

6. Agent software on computer-readable medium, said agent software for running on a master host processor which is one of a plurality of processors connected to a data storage system, said plurality of processors all having access to a shared storage area in the data storage system and each being connected to said data storage system through a corresponding different channel, said agent software comprising:

means for receiving an access request from another one of said plurality of processors, said access request being a request to access an identified object in the shared storage area of the data storage system;

means for determining whether any conflicting locks are pending for the identified object stored within the shared storage area of the data storage system;

means for granting the access request from the requesting processor if it is determined that no conflicting locks are pending for any other processor; and

means for notifying the requesting processor whether its access request was granted.

7. The agent software of claim 6 further comprising means for denying the access request from the requesting processor if it is determined that a conflicting lock is pending for another processor, and wherein the notifying means notifies the requesting processor whether its access request was granted or denied.

8. The agent software of claim 7 wherein the object is a file system.

9. The agent software of claim 8 wherein the access request is a request to access a file in the file system.

10. Interface software on computer-readable medium, said interface software for running on a slave processor which is one of a plurality of processors connected to a data storage system, said plurality of host processors all having access to a shared storage area in the data storage system and each being connected to said data storage system through a corresponding different channel, said interface software comprising:

means for preventing said slave processor from accessing an identified object stored in the shared storage area when no authorization has been received from a master processor which is another one of said plurality of processors;

means for sending an access request from the slave processor to the master processor, said access request being a request for accessing said identified object in the shared storage area;

means for receiving an acknowledgment from the master processor indicating whether the access request was granted; and

means for permitting the slave processor to access the object if the received acknowledgment grants the access request.

11. The interface software of claim 10 further comprising means for notifying the master processor when an access operation involving the object is complete.

12. The interface software of claim 11 wherein the object is a file system.

13. The interface software of claim 12 wherein the access request is a request to access a file in the file system.

14. An access control method running on a processor which is one of a plurality of processors connected to a data storage system, said plurality of processors all having access to a shared storage area in the data storage system and each being connected to said data storage system through a corresponding different channel, said access control method comprising:

receiving an access request from another one of said plurality of processors, said access request being a request to access an identified object stored in the shared storage area of the data storage system;

determining whether any conflicting locks are pending for the identified object stored within the shared storage area of the data storage system;

granting the access request from the requesting processor if it is determined that no conflicting locks are pending for any other processor; and

notifying the requesting host processor whether its access request was granted.

15. The method of claim 14 further comprising denying the access request from the requesting processor if it is determined that a conflicting lock is pending for another processor, and wherein the step of notifying comprises notifying the requesting processor whether its access request was granted or denied.

16. The method of claim 15 wherein the object is a file system.

17. The method of claim 16 wherein the access request is a request to access a file in the file system.

18. An access control method running on a slave processor which is one of a plurality of processors connected to a data storage system, said plurality of processors all having access to a shared storage area in the data storage system and each being connected to said data storage system through a corresponding different channel, said method comprising:

preventing said slave processor from accessing an identified object stored in the shared storage area when no authorization has been received from a master processor which is another one of said plurality of processors;

sending an access request from the slave processor to the master processor, said access request being a request for accessing said identified object in the shared storage area;

receiving an acknowledgment from the master processor indicating whether the access request was granted; and

permitting the slave processor to access the object if the received acknowledgment grants the access request.

19. The method of claim 18 further comprising notifying the master processor when an access operation involving the object is complete.

20. The method of claim 19 wherein the object is a file system.

21. The method of claim 20 wherein the access request is a request to access a file in the file system.