Method and system for providing access to a shared resource utilizing selective locking

• US 20070061810A1
• Filed: 09/15/2005
• Published: 03/15/2007
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Srinivas, Mysore, Mewhinney, Greg, Mehaffy, David
• Granted Patent: US 8,225,327 B2
• Time in Patent Office: Days
• US Class Current: 718/104
• CPC Class Codes: G06F 9/3004 to perform operations on memory
• CPC Class Codes: G06F 9/30072 to perform conditional operations, e.g. using predicates or guards
• CPC Class Codes: G06F 9/30087 Synchronisation or serialisation instructions
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: G06F 9/544 Buffers; Shared memory; Pipes

Abstract

A method and system for providing access to a shared resource utilizing selective locking are disclosed. According to one embodiment, a method is provided comprising receiving a request to perform a resource access operation on a shared resource, invoking a first routine to perform the resource access operation, detecting a data processing system exception generated in response to invoking the first routine, and invoking a second routine to perform the resource access operation in response to such detecting. In the described embodiment, the first routine comprises a dereference instruction to dereference a pointer to memory associated with the shared resource, the second routine comprises a lock acquisition instruction to acquire a global lock associated with the shared resource prior to a performance of the resource access operation and a lock release instruction to release the global lock once resource access operation has been performed.

Claims

1. A method of providing access to a shared resource within a data processing system, said method comprising:

receiving a request to perform a resource access operation on said shared resource;

invoking a first routine to perform said resource access operation in response to said receiving, wherein said first routine comprises a dereference instruction to dereference a pointer to memory associated with said shared resource;

detecting a data processing system exception generated in response to invoking said first routine;

invoking a second routine to perform said resource access operation in response to said detecting, wherein said second routine comprises a lock acquisition instruction to acquire a global lock associated with said shared resource prior to a performance of said resource access operation and a lock release instruction to release said global lock subsequent to said performance of said resource access operation.

2. The method of claim 1, wherein,

said shared resource comprises a list data structure comprising one or more list elements,

receiving said request to perform said resource access operation comprises receiving a request to remove a first list element of said one or more list elements from said list data structure, and

said pointer to memory comprises a pointer to a second list element of said one or more list elements.

3. The method of claim 2, wherein said detecting comprises detecting a memory page fault.

4. The method of claim 2, wherein said first routine comprises a load-and-reserve instruction and a store-conditional instruction utilized in combination to atomically access a pointer to said first list element of said one or more list elements.

5. The method of claim 2, wherein

said method further comprises

invoking a third routine to deallocate said memory associated with said shared resource, and

said dereference instruction is executed subsequent to an invocation of said third routine.

6. The method of claim 5, wherein said third routine comprises said lock acquisition instruction to acquire said global lock associated with said shared resource, a deallocation instruction to deallocate said memory associated with said shared resource, and a lock release instruction to release said global lock in response to an execution of said deallocation instruction.

7. The method of claim 2, further comprising generating a synchronization element associated with said global lock in response to a generation of said list data structure.

8. The method of claim 2, wherein

said first routine comprises a non-global-locking version of a list data structure element removal execution sequence,

said second routine comprises a global-locking version of said list data structure element removal execution sequence, and

invoking said second routine comprises invoking said global-locking version of said list data structure element removal execution sequence in response to a dereferencing of deallocated memory occurring as a result of execution of said non-global-locking version of said list data structure element removal execution sequence.

9. An apparatus configured to provide access to a shared resource comprising:

means for receiving a request to perform a resource access operation on said shared resource;

means for invoking a first routine to perform said resource access operation in response to a reception of said request, wherein said first routine comprises a dereference instruction to dereference a pointer to memory associated with said shared resource;

means for detecting a data processing system exception generated in response to an invocation of said first routine;

means for invoking a second routine to perform said resource access operation in response to a detection of said data processing system exception, wherein said second routine comprises a lock acquisition instruction to acquire a global lock associated with said shared resource prior to a performance of said resource access operation and a lock release instruction to release said global lock subsequent to said performance of said resource access operation.

10. The apparatus of claim 9, wherein,

said shared resource comprises a list data structure comprising one or more list elements,

said means for receiving said request to perform said resource access operation comprises means for receiving a request to remove a first list element of said one or more list elements from said list data structure, and

said pointer to memory comprises a pointer to a second list element of said one or more list elements.

11. The apparatus of claim 10, wherein said means for detecting comprises means for detecting a memory page fault.

12. The apparatus of claim 10, wherein said first routine comprises a load-and-reserve instruction and a store-conditional instruction utilized in combination to atomically access a pointer to said first list element of said one or more list elements.

13. The apparatus of claim 10, wherein

said apparatus further comprises

means for invoking a third routine to deallocate said memory associated with said shared resource, and

said dereference instruction is executed subsequent to an invocation of said third routine.

14. The apparatus of claim 13, wherein said third routine comprises said lock acquisition instruction to acquire said global lock associated with said shared resource, a deallocation instruction to deallocate said memory associated with said shared resource, and a lock release instruction to release said global lock in response to an execution of said deallocation instruction.

15. The apparatus of claim 10, further comprising means for generating a synchronization element associated with said global lock in response to a generation of said list data structure.

16. The apparatus of claim 10, wherein

said first routine comprises a non-global-locking version of a list data structure element removal execution sequence,

said second routine comprises a global-locking version of said list data structure element removal execution sequence, and

said means for invoking said second routine comprises means for invoking said global-locking version of said list data structure element removal execution sequence in response to a dereferencing of deallocated memory occurring as a result of execution of said non-global-locking version of said list data structure element removal execution sequence.

17. A machine-readable medium having a plurality of instructions executable by a machine embodied therein, wherein said plurality of instructions when executed cause said machine to perform a method of providing access to a shared resource within a data processing system, said method comprising:

receiving a request to perform a resource access operation on said shared resource;

invoking a first routine to perform said resource access operation in response to said receiving, wherein said first routine comprises a dereference instruction to dereference a pointer to memory associated with said shared resource;

detecting a data processing system exception generated in response to invoking said first routine;

invoking a second routine to perform said resource access operation in response to said detecting, wherein said second routine comprises a lock acquisition instruction to acquire a global lock associated with said shared resource prior to a performance of said resource access operation and a lock release instruction to release said global lock subsequent to said performance of said resource access operation.

18. The machine-readable medium of claim 17, wherein,

said shared resource comprises a list data structure comprising one or more list elements,

receiving said request to perform said resource access operation comprises receiving a request to remove a first list element of said one or more list elements from said list data structure, and

said pointer to memory comprises a pointer to a second list element of said one or more list elements.

19. The machine-readable of claim 18, wherein said first routine comprises a load-and-reserve instruction and a store-conditional instruction utilized in combination to atomically access a pointer to said first list element of said one or more list elements.

20. The machine-readable medium of claim 18, wherein

said method further comprises

invoking a third routine to deallocate said memory associated with said shared resource, wherein said third routine comprises

said lock acquisition instruction to acquire said global lock associated with said shared resource,

a deallocation instruction to deallocate said memory associated with said shared resource, and

a lock release instruction to release said global lock in response to an execution of said deallocation instruction,

said dereference instruction is executed subsequent to an invocation of said third routine.