Methods, apparatus and articles of manufacture for regaining memory consistency after a trap via transactional memory

• US 8,032,736 B2
• Filed: 02/26/2008
• Issued: 10/04/2011
• Est. Priority Date: 02/26/2008
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Abrashkevich, Alexander, Abrashkevich, Dmitri, Srivastava, Yogendra K., Blainey, Robert J., Munireddy, Sridhar, Huras, Matthew A., Wilding, Mark F., Heller, Thomas J. Jr.
• Primary Examiner(s): PAN, DANIEL H
• Application Number:
  US12/037,888
• Publication Number:
  US 20090217018A1
• Time in Patent Office: 1,316 Days
• Field of Search: 712/228, 712/244
• US Class Current: 712/228
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence
• CPC Class Codes: G06F 9/467 Transactional memory G06F9/528 takes precedence

Abstract

Embodiments of the invention provide a method for regaining memory consistency after a trap via transactional memory. Transactional memory and a transactional memory log are used to undo changes made to memory from a transaction start point up to the point of a trap event. After the trap event is processed, and the changes are rolled back, the program can resume execution at the beginning of the transaction.

Claims

1. A method for regaining memory consistency after a trap event, the method comprising:

initiating, by a thread, a transaction including a plurality of instructions;

recording a sequence of changes made to memory while executing the plurality of instructions;

detecting an occurrence of a trap event prior to completing the transaction;

passing an error code to the thread indicating a type of error that caused the trap event;

rolling back the sequence of changes made to the memory up to a first instruction of the transaction, based on the recorded sequence; and

resuming execution of the thread at the first instruction of the transaction.

2. The method of claim 1, further comprising invoking a trap-handler associated with the trap event prior to resuming execution of the thread at the first instruction of the transaction.

3. The method of claim 1, further comprising:

determining whether the transaction has been initiated and rolled back, on the basis of the trap event, more than a specified a number of times; and

terminating the thread if the number of interruptions has exceeded a predetermined threshold.

4. The method of claim 1, wherein the transactional memory is software-based transactional memory.

5. The method of claim 1, wherein the transactional memory is hardware-based transactional memory.

6. The method of claim 1, wherein the trap event is generated in response to one of an invalid memory reference, a divide-by-zero error, a hardware event, and a user-generated interrupt.

7. The method of claim 1, wherein the plurality of instructions included in the transaction represent an atomic sequence of steps to be performed without interruption.

8. The method of claim 1, wherein passing the error code to the thread indicating the type of error that caused the trap event occurs prior to the execution of the thread at the first instruction of the transaction being resumed.

9. A computer-readable storage medium containing a program that when executed performs an operation for regaining memory consistency after a trap event, the operation comprising:

initiating, by a thread, a transaction including a plurality of instructions;

recording a sequence of changes made to memory while executing the plurality of instructions;

detecting an occurrence of a trap event prior to completing the transaction;

passing an error code to the thread indicating a type of error that caused the trap event;

rolling back the sequence of changes made to the memory up to a first instruction of the transaction, based on the recorded sequence; and

resuming execution of the thread at the first instruction of the transaction.

10. The computer-readable storage medium of claim 9, wherein the operation further comprises-invoking a trap-handler associated with the trap event prior to resuming execution of the thread at the first instruction of the transaction.

11. The computer-readable storage medium of claim 9, wherein the operation further comprises:

determining whether the transaction has been initiated and rolled back, on the basis of the trap event, more than a specified a number of times; and

terminating the thread if the number of interruptions has exceeded a predetermined threshold.

12. The computer-readable storage medium of claim 9, wherein the transactional memory is software-based transactional memory.

13. The computer-readable storage medium of claim 9, wherein the transactional memory is hardware-based transactional memory.

14. The computer-readable storage medium of claim 9, wherein the trap event is generated in response to one of an invalid memory reference, a divide-by-zero error, a hardware event, and a user-generated interrupt.

15. The computer-readable storage medium of claim 9, wherein the plurality of instructions included in the transaction represent an atomic sequence of steps to be performed without interruption.

16. The computer-readable storage medium of claim 9, wherein passing the error code to the thread indicating the type of error that caused the trap event occurs prior to the execution of the thread at the first instruction of the transaction being resumed.

17. A system comprising:

a processor;

a transactional memory; and

a transactional memory manager configured to perform an operation for regaining memory consistency after a trap event via the transactional memory, the operation comprising;

initiating, by a thread, a transaction including a plurality of instructions;

recording a sequence of changes made to the transactional memory while executing the plurality of instructions;

detecting an occurrence of a trap event prior to completing the transaction;

passing an error code to the thread indicating a type of error that caused the trap event;

rolling back the sequence of changes made to the transactional memory up to a first instruction of the transaction, based on the recorded sequence; and

resuming execution of the thread at the first instruction of the transaction.

18. The system of claim 17, wherein the operation further comprises invoking a trap-handler associated with the trap event prior to resuming execution of the thread at the first instruction of the transaction.

19. The system of claim 17, wherein the operation further comprises:

determining whether the transaction has been initiated and rolled back, on the basis of the trap event, more than a specified a number of times; and

terminating the thread if the number of interruptions has exceeded a predetermined threshold.

20. The system of claim 17, wherein the transactional memory is software-based transactional memory.

21. The system of claim 17, wherein the transactional memory is hardware-based transactional memory.

22. The system of claim 17, wherein the trap event is generated in response to one of an invalid memory reference, a divide-by-zero error, a hardware event, and a user-generated interrupt.

23. The system of claim 17, wherein the plurality of instructions included in the transaction represent an atomic sequence of steps to be performed without interruption.

24. The system of claim 17, wherein passing the error code to the thread indicating the type of error that caused the trap event occurs prior to the execution of the thread at the first instruction of the transaction being resumed.