Method of controlling thread access to a synchronization object

• US 8,132,171 B2
• Filed: 12/22/2006
• Issued: 03/06/2012
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Ruemmler, Christopher P.
• Primary Examiner(s): An, Meng
• Assistant Examiner(s): ZHE, MENG YAO
• Application Number:
  US11/615,935
• Publication Number:
  US 20080155546A1
• Time in Patent Office: 1,901 Days
• Field of Search: 718/102
• US Class Current: 718/102
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

A method of controlling thread access to a synchronization object is described. The method comprises waking a sleeping first thread after release, by a second thread, of a synchronization object in a normal state and causing, by the first thread, the synchronization object to transition to a want-lock state, the synchronization object being acquirable by the first thread prior to being acquirable by the second thread.

Claims

1. A method of controlling thread access to a synchronization object, comprising:

sending a signal to wake a sleeping first thread after a second thread releases a synchronization object; and

setting, by the second thread, a value of the synchronization object to transition the synchronization object to an in-flight state indicating that the synchronization object is available to be acquired, the first thread to remain awake for a predetermined time if a third thread acquires the synchronization object in the in-flight state before the first thread acquires the synchronization object in the in-flight state, wherein the in-flight state is where the second thread has released the synchronization object and the first thread has received a wake up signal but before the first thread is able to execute; and

setting, by the first thread, the value of the synchronization object to transition the synchronization object from the in-flight state to a want-lock state indicating that the synchronization object is only available to be acquired by the first thread after the third thread releases the synchronization object.

2. The method as claimed in claim 1, further comprising:

acquiring, by the first thread, the synchronization object in the in-flight state before the predetermined time elapses and before the third thread acquires the synchronization object.

3. The method as claimed in claim 1, wherein sending the signal to wake the sleeping first thread occurs after the synchronization object transitions to the in-flight state.

4. The method as claimed in claim 1, further comprising:

acquiring, by the third thread, the synchronization object before the synchronization object transitions to the want-lock state; and

releasing, by the third thread, the synchronization object after the synchronization object transitions to the want-lock state, wherein the synchronization object remains in the want-lock state after the third thread releases the synchronization object.

5. The method as claimed in claim 4, further comprising:

acquiring, by the first thread, the synchronization object in the want-lock state.

6. The method as claimed in claim 1, wherein sending the signal to wake the sleeping first thread further comprises:

selecting the sleeping first thread from a sleeping thread list according to a predetermined order.

7. The method as claimed in claim 6, wherein the predetermined order comprises a first-in, first-out order.

8. The method as claimed in claim 1, further comprising:

causing, by the first thread, the synchronization object to transition to a normal state that indicates that the synchronization object is available to be acquired, if the first thread sleeps prior to acquiring the synchronization object.

9. The method as claimed in claim 8, wherein the first thread sleeps if a spin threshold value is exceeded.

10. The method as claimed in claim 9, wherein the spin threshold value is exceeded by at least one of a number of attempts to acquire the synchronization object or elapse of the predetermined time.

11. The method as claimed in claim 9, wherein the spin threshold value is modified by a value for each unsuccessful attempt to acquire the synchronization object by the first thread.

12. The method as claimed in claim 1, wherein the synchronization object is acquirable by the first thread before the synchronization object is acquirable by the second thread.

13. A tangible computer-readable storage medium storing instructions that, when executed, cause a processor to at least:

implement a synchronization object comprising a state parameter indicating a state of the synchronization object, the state parameter configured to transition the state to at least an in-flight state indicating that the synchronization object is available to be acquired by any thread not sleeping, wherein the in-flight state is where a first thread has released the synchronization object and a second thread has received a wake up signal but before the second thread is able to execute, and the state parameter is configured to transition the state of the synchronization object from the in-flight state to a want-lock state, the want-lock state to indicate that the synchronization object is only available to be acquired by the second thread after a third thread acquires and releases the synchronization object.

14. The computer-readable storage medium as claimed in claim 13, wherein the synchronization object further comprises a lock parameter indicating that the synchronization object is in either a locked state or an unlocked state, and wherein at least one thread is to attempt to acquire the synchronization object if the synchronization object is in an unlocked state.

15. The computer-readable storage medium as claimed in claim 13, wherein the state parameter of the synchronization object is further configured to transition the synchronization object to a want-lock state indicating that the synchronization object is available to be acquired only by a most recently awakened thread.

16. The computer-readable storage medium as claimed in claim 15, wherein the instructions, when executed, cause the processor to implement a thread having a wake state parameter, the thread to attempt to acquire the synchronization object if the state of the synchronization object is in-flight or the wake state parameter indicates the thread is the most recently awakened thread and the state is want-lock.

17. The computer-readable storage medium as claimed in claim 16, wherein the thread further comprises a spin threshold.

18. The computer-readable storage medium as claimed in claim 17, wherein the spin threshold indicates at least one of a number of attempts to acquire the synchronization object or elapse of the predetermined time.

19. The computer-readable storage medium as claimed in claim 16, wherein the instructions, when executed, cause the processor to apply a formula to the spin threshold for each unsuccessful attempt to acquire the synchronization object by the thread.

20. The computer-readable storage medium as claimed in claim 16, wherein the thread is to set the state of the synchronization object to the in-flight state after release of the synchronization object.

21. The computer-readable storage medium as claimed in claim 20, wherein the thread is to wake another sleeping thread.

22. A tangible computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to at least:

send a signal to wake a sleeping first thread;

release, by a second thread, a synchronization object; and

set, by the second thread, a value of the synchronization object to transition the synchronization object to an in-flight state indicating that the synchronization object is available to be acquired, the first thread to remain awake for a predetermined time if a third thread acquires the synchronization object in the in-flight state before the first thread acquires the synchronization object in the in-flight state, wherein the in-flight state is where the second thread has released the synchronization object and the first thread has received a wake up signal but before the first thread is able to execute; and

set, by the first thread, the value of the synchronization object to transition the synchronization object from the in-flight state to a want-lock state indicating that the synchronization object is only available to be acquired by the first thread after the third thread releases the synchronization object.

23. The computer-readable storage medium as claimed in claim 22, wherein the instructions, when executed, cause the processor to send the signal to wake the sleeping first thread after the synchronization object is released.