RUNTIME CODE MODIFICATION IN A MULTI-THREADED ENVIRONMENT

• US 20080052697A1
• Filed: 08/21/2007
• Published: 02/28/2008
• Est. Priority Date: 08/28/2006
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Stoodley, Kevin Alexander, Stoodley, Mark Graham
• Granted Patent: US 8,589,900 B2
• Time in Patent Office: Days
• US Class Current: 717/159
• CPC Class Codes: G06F 9/3851 from multiple instruction streams, e.g. multistreaming

Abstract

A code region forming part of a computer program is modified during execution of the computer program by a plurality of threads. In one aspect, identical modification instructions are provided to each thread for modifying a site in the code region having a desirable idempotent atomic modification, and the modification instructions direct each thread to make the desirable idempotent atomic modification. In another aspect, a thread is selected to modify the code region, each thread other than the selected thread is directed to execute an alternative execution path that generates output identical to the output of the code region after the code region has been modified, and, responsive to directing each thread other than the selected thread, the selected thread is directed to modify the code region.

Claims

1. A method for making a desirable idempotent atomic modification to a site in a code region forming part of a computer program during execution of the computer program by a plurality of threads, the method comprising providing identical modification instructions to each thread for modifying the site in the code region, wherein the modification instructions direct each thread to make the desirable idempotent atomic modification.

2. The method of claim 1, wherein the desirable idempotent atomic modification is generated from a desirable idempotent non-atomic modification by NOP insertion.

3. The method of claim 1, wherein the modification instructions are adapted so that, responsive to completion of the desirable idempotent atomic modification, the modification instructions are negated.

4. A method for making a desirable modification to a code region forming part of a computer program during execution of the computer program by a plurality of threads, the method comprising:

selecting a thread to modify the code region to form a selected thread;

directing each thread other than the selected thread to follow an alternative execution path that generates output identical to output of the code region after the desirable modification has been made to the code region; and

responsive to directing each thread other than the selected thread, directing the selected thread to make the desirable modification to the code region so as to generate a modified code region.

5. The method of claim 4, further comprising, prior to the step of directing each thread other than the selected thread, generating the alternative execution path.

6. The method of claim 4, wherein the alternative execution path is a pre-existing general call associated with the code region.

7. The method of claim 4, further comprising, responsive to completion of modification of the code region by the selected thread, directing each thread to execute the modified code region.

8. The method of claim 4, wherein the step of selecting a thread to modify the code region to form a selected thread comprises initially enabling thread access to a point associated with the code region wherein the point is adapted so that an arbitrary first thread to reach the point becomes the selected thread.

9. A method for causing a desirable idempotent atomic modification to be made to a site in a code region forming part of a computer program during execution of the computer program by a plurality of threads, the method comprising including in the code region a call to a set of modification instructions so that each thread reaching the call will make the desirable idempotent atomic modification.

10. The method of claim 9, wherein the desirable idempotent atomic modification is generated from a desirable idempotent non-atomic modification by NOP insertion.

11. The method of claim 9, wherein the modification instructions are adapted to negate the call responsive to completion of the desirable idempotent atomic modification.

12. A method for causing a desirable modification to be made to a code region forming part of a computer program during execution of the computer program by a plurality of threads, the method comprising:

including in the code region a call to a set of instructions whereby an arbitrary thread that executes the call will become a selected thread,

wherein the instructions, when executed,

direct each thread other than the selected thread to follow an alternative execution path that generates output identical to output of the code region after the desirable modification has been made to the code region; and

responsive to directing each thread other than the selected thread, direct the selected thread to make the desirable modification to the code region so as to generate a modified code region.

13. The method of claim 12, wherein the instructions, when executed, generate the alternative execution path before each thread other than the selected thread is directed to the alternative execution path.

14. The method of claim 12, wherein the alternative execution path is a pre-existing general call associated with the code region.

15. The method of claim 12, wherein the instructions, when executed, direct each thread to execute the modified code region in response to completion of modification of the code region by the selected thread.

16. The method of claim 12, wherein the arbitrary thread is a first thread to reach the call.