Eliminating synchronous grace period detection for non-preemptible read-copy update on uniprocessor systems

• US 8,195,893 B2
• Filed: 11/03/2008
• Issued: 06/05/2012
• Est. Priority Date: 11/03/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Triplett, Joshua A.
• Primary Examiner(s): Bragdon, Reginald
• Assistant Examiner(s): Loonan, Eric
• Application Number:
  US12/263,613
• Publication Number:
  US 20100115235A1
• Time in Patent Office: 1,310 Days
• Field of Search: None
• US Class Current: 711/147
• CPC Class Codes: G06F 9/466 Transaction processing
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores

Abstract

A technique for optimizing grace period detection in a uniprocessor environment. An update operation is performed on a data element that is shared with non-preemptible readers of the data element. A call is issued to a synchronous grace period detection method. The synchronous grace period detection method performs synchronous grace period detection and returns from the call if the data processing system implements a multi-processor environment at the time of the call. The synchronous grace period detection determines the end of a grace period in which the readers have passed through a quiescent state and cannot be maintaining references to the pre-update view of the shared data. The synchronous grace period detection method returns from the call without performing grace period detection if the data processing system implements a uniprocessor environment at the time of the call.

Claims

1. A method for use in a data processing system, comprising:

performing an update operation on a data element that is shared with one or more non-preemptible readers of said data element;

issuing a call to a synchronous grace period detection method;

said synchronous grace period detection method performing synchronous grace period detection and returning from said call if said data processing system implements a multi-processor environment at a time of said call;

said synchronous grace period detection determining an end of a grace period in which said one or more non-preemptible readers have passed through a quiescent state and cannot be maintaining references to a pre-update view of said shared data element; and

said synchronous grace period detection method returning from said call without performing grace period detection if said data processing system implements a uniprocessor environment at the time of said call.

2. The method of claim 1, wherein said synchronous grace period detection method is configured at compile time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is compiled for said multiprocessor environment or said uniprocessor environment.

3. The method of claim 1, wherein said synchronous grace period detection method is configured at run time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is called in said multiprocessor environment or said uniprocessor environment.

4. The method of claim 1, wherein said synchronous grace period detection method is configured based on system configuration information provided at compile time, at boot time or at run time.

5. The method of claim 1, wherein said synchronous grace period detection method for said uniprocessor environment implements one or more instructions to prevent reordering of said call to said synchronous grace period detection method with an instruction pertaining to said update operation on said data element.

6. A data processing system, comprising:

one or more processors;

a memory coupled to said one or more processors, said memory including a computer useable medium tangibly embodying at least one program of instructions executable by said one or more processors to perform operations for optimizing grace period detection following a data element update operation that affects non-preemptible data readers, comprising;

performing an update operation on a data element that is shared with one or more non-preemptible readers of said data element;

issuing a call to a synchronous grace period detection method;

said synchronous grace period detection method performing synchronous grace period detection and returning from said call if said data processing system implements a multi-processor environment at a time of said call;

said synchronous grace period detection determining an end of a grace period in which said one or more non-preemptible readers have passed through a quiescent state and cannot be maintaining references to a pre-update view of said shared data element; and

said synchronous grace period detection method returning from said call without performing grace period detection if said data processing system implements a uniprocessor environment at the time of said call.

7. The system of claim 6, wherein said uniprocessor environment is a multi-processor system having not more than one processor in an operational mode executing any of said one or more non-preemptible readers.

8. The system of claim 7, wherein said synchronous grace period detection method is configured at compile time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is compiled for said multiprocessor environment or said uniprocessor environment.

9. The system of claim 6, wherein said synchronous grace period detection method is configured at run time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is called in said multiprocessor environment or said uniprocessor environment.

10. The system of claim 6, wherein said synchronous grace period detection method is configured based on system configuration information provided at compile time, at boot time or at run time.

11. The system of claim 6, wherein said synchronous grace period detection method for said uniprocessor environment implements one or more instructions to prevent reordering of said call to said synchronous grace period detection method with an instruction pertaining to said update operation on said data element.

12. A computer program product, comprising:

one or more machine-readable storage media;

means provided by said one or more media for programming a data processing platform to optimize grace period detection following a data element update operation that affects non-preemptible data readers, as by;

performing an update operation on a data element that is shared with one or more non-preemptible readers of said data element;

issuing a call to a synchronous grace period detection method;

said synchronous grace period detection method performing synchronous grace period detection and returning from said call if said data processing platform implements a multi-processor environment at a time of said call;

said synchronous grace period detection determining an end of a grace period in which said one or more non-preemptible readers have passed through a quiescent state and cannot be maintaining references to a pre-update view of said shared data element; and

said synchronous grace period detection method returning from said call without performing grace period detection if said data processing platform implements a uniprocessor environment at the time of said call.

13. The computer program product of claim 12, wherein said uniprocessor environment is a multi-processor system having not more than one processor in an operational mode executing any of said one or more non-preemptible readers.

14. The computer program product of claim 13, wherein said synchronous grace period detection method is configured at compile time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is compiled for said multiprocessor environment or said uniprocessor environment.

15. The computer program product of claim 12, wherein said synchronous grace period detection method is configured at run time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is called in said multiprocessor environment or said uniprocessor environment.

16. The computer program product of claim 12, wherein said synchronous grace period detection method is configured based on system configuration information provided at compile time, at boot time or at run time.

17. The computer program product of claim 12, wherein said synchronous grace period detection method for said uniprocessor environment implements one or more instructions to prevent reordering of said call to said synchronous grace period detection method with an instruction pertaining to said update operation on said data element.

18. A method for optimizing grace period detection following a data element update operation in a data processing system having non-preemptible readers, comprising:

performing an update operation on a data element that is shared with one or more non-preemptible readers of said data element;

issuing a call to a synchronous grace period detection method;

said synchronous grace period detection method performing synchronous grace period detection and returning from said call if said data processing system implements a multi-processor environment at a time of said call;

said synchronous grace period detection determining an end of a grace period in which said one or more non-preemptible readers have passed through a quiescent state and cannot be maintaining references to said pre-update view of said shared data;

said synchronous grace period detection method returning from said call without performing grace period detection if said data processing system implements a uniprocessor environment at the time of said call; and

said uniprocessor environment being a multi-processor system having not more than one processor in an operational mode executing any of said one or more non-preemptible readers.

19. The method of claim 18, wherein said synchronous grace period detection method is configured at one of:

compile time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is compiled for said multiprocessor environment or said uniprocessor environment;

or

run time to perform or not perform said grace period detection based on whether said synchronous grace period detection method is called in said multiprocessor environment or said uniprocessor environment.