Wake-and-Go Mechanism with Data Exclusivity

• US 20090199028A1
• Filed: 02/01/2008
• Published: 08/06/2009
• Est. Priority Date: 02/01/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Arimilli, Ravi K., Sharma, Satya P., Swanberg, Randal C.
• Granted Patent: US 8,225,120 B2
• Time in Patent Office: Days
• US Class Current: 713/323
• CPC Class Codes: G06F 12/0831 using a bus scheme, e.g. with bus monitoring or watching means
• CPC Class Codes: G06F 2209/521 Atomic
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Snoop response logic on a system bus is configured to detect on the system bus requests to access data at a target address with data exclusivity from at least one of a plurality of wake-and-go engines. The snoop response logic is further configured to determine a winning wake-and-go engine from the at least one wake-and-go engine that obtains a lock on the target address and generate a combined snoop response. The combined snoop response identifies the winning wake-and-go engine. The snoop response logic sends the combined snoop response to the at least one wake-and-go engine on the system bus. Each remaining wake-and-go engine within the at least one wake-and-go engine places an entry in its respective wake-and-go storage array to spin on a lock for the target address.

Claims

1. A method, in a data processing system, for determining data exclusivity for wake-and-go engines, the method comprising:

detecting on a system bus requests to access data at a target address with data exclusivity from at least one wake-and-go engine;

determining a winning wake-and-go engine from the at least one wake-and-go engine that obtains a lock for the target address;

generating a combined snoop response, wherein the combined snoop response identifies the winning wake-and-go engine; and

sending the combined snoop response to the at least one wake-and-go engine on the system bus such that each remaining wake-and-go engine within the at least one wake-and-go engine places an entry in its respective wake-and-go storage array to spin on a lock for the target address.

2. The method of claim 1, further comprising:

detecting on the system bus a subsequent request to access the data by a given wake-and-go engine;

generating a subsequent combined snoop response, wherein the combined snoop response identifies the winning wake-and-go engine; and

sending the subsequent combined snoop response to the given wake-and-go engine on the system bus.

3. The method of claim 2, wherein the subsequent request to access the data requests data exclusivity.

4. The method of claim 3, wherein the given wake-and-go engine places an entry in its respective wake-and-go storage array to spin on the lock for the target address.

5. The method of claim 1, further comprising:

detecting on the system bus that the winning wake-and-go engine releases a lock on the data;

generating a subsequent combined snoop response, wherein the combined snoop response indicates that the winning wake-and-go engine released the lock for the target address; and

sending the subsequent combined snoop response on the system bus.

6. The method of claim 5, wherein responsive to detecting the subsequent combines snoop response, each remaining wake-and-go engine within the at least one wake-and-go engine contends for the lock for the target address.

7. The method of claim 1, wherein the subsequent request to access the data is a look-ahead load command.

8. The method of claim 7, wherein the look-ahead load command is a load without reservation command.

9. The method of claim 7, wherein the look-ahead load command is a specialized bus command indicating that the given wake-and-go engine is performing a look-ahead polling operation without caching or data exclusivity.

10. The method of claim 7, wherein responsive to receiving the subsequent combines snoop response the given wake-and-go engine populates its respective wake-and-go storage array with the target address.

11. A data processing system, comprising:

a plurality of wake-and-go engines, wherein each of the plurality of wake-and-go engines is associated with a processor and has a respective wake-and-go storage array;

a system bus; and

snoop response logic on the system bus, wherein the snoop response logic is configured to;

detect on the system bus requests to access data at a target address with data exclusivity from at least one of the plurality of wake-and-go engines;

determine a winning wake-and-go engine from the at least one wake-and-go engine that obtains a lock on the target address;

generate a combined snoop response, wherein the combined snoop response identifies the winning wake-and-go engine; and

send the combined snoop response to the at least one wake-and-go engine on the system bus such that each remaining wake-and-go engine within the at least one wake-and-go engine places an entry in its respective wake-and-go storage array to spin on a lock for the target address.

12. The data processing system of claim 11, wherein the snoop response logic is further configured to:

detect on the system bus a subsequent request to access the data by a given wake-and-go engine within the plurality of wake-and-go engines;

generate a subsequent combined snoop response, wherein the combined snoop response identifies the winning wake-and-go engine; and

send the subsequent combined snoop response to the given wake-and-go engine on the system bus.

13. The data processing system of claim 12, wherein the subsequent request to access the data requests data exclusivity.

14. The data processing system of claim 13, wherein the given wake-and-go engine places an entry in its respective wake-and-go storage array to spin on the lock for the target address.

15. The data processing system of claim 11, wherein the snoop response logic is further configured to:

detect on the system bus that the winning wake-and-go engine releases a lock on the data;

generate a subsequent combined snoop response, wherein the combined snoop response indicates that the winning wake-and-go engine released the lock on the target address; and

send the subsequent combined snoop response on the system bus.

16. The data processing system of claim 15, wherein responsive to detecting the subsequent combines snoop response, each remaining wake-and-go engine within the at least one wake-and-go engine contends for the lock on the target address.

17. The data processing system of claim 11, wherein the subsequent request to access the data is a look-ahead load command.

18. The data processing system of claim 17, wherein the look-ahead load command is a load without reservation command.

19. The data processing system of claim 17, wherein the look-ahead load command is a specialized bus command indicating that the given wake-and-go engine is performing a look-ahead polling operation without caching or data exclusivity.

20. The data processing system of claim 17, wherein responsive to receiving the subsequent combines snoop response the given wake-and-go engine populates its respective wake-and-go storage array with the target address.