PRIORITY ROLLBACK PROTOCOL

• US 20120005684A1
• Filed: 06/30/2011
• Published: 01/05/2012
• Est. Priority Date: 07/02/2010
• Status: Abandoned Application

• Current Assignee: FIJI Systems, Inc.
• Original Assignee: FIJI Systems, Inc.
• Inventors: Ziarek, Lukasz
• Application Number:
  US13/173,293
• Publication Number:
  US 20120005684A1
• Time in Patent Office: Days
• US Class Current: 718/103
• CPC Class Codes: G06F 9/528 by using speculative mechanisms

Abstract

Mechanisms for enforcing limits to resource access are provided. In some embodiments, synchronization tools are used to reduce the worst case execution time of selected processing sequences. In one example, instructions from a first processing sequence are rolled back using rollback information stored in a data structure if a higher priority processing sequence seeks access to the resource.

Claims

1. A method executable with a processing device according to processing instructions embedded in a non-transitory computer readable medium to prevent concurrent access to a software resource by a first thread and a second thread, the method comprising:

executing a critical region of the first thread;

writing rollback information to a rollback data structure based on the executing of the critical region of the first thread;

detecting an indication that the second thread seeks access to the software resource; and

after detecting the indication, rolling back the executing of the critical region of the first thread.

2. A method as in claim 1, further comprising the step of controlling operation of a hardware resource with the software resource.

3. A method as in claim 1, wherein the first thread has a lower priority than the second thread, and wherein rolling back the executing of the critical region reduces a worst case execution time of the second thread.

4. A method as in claim 1, wherein the rollback data structure is a buffer and the step of rolling back the executing of the critical region of the first thread includes releasing a synchronization tool without flushing the buffer.

5. A method as in claim 4, further comprising the steps of flushing the buffer and modifying a status indicator of the synchronization tool to indicate that flushing begun, wherein if flushing begun before the indication is detected in the detecting step, the second thread cannot access the software resource until the flushing step is complete.

6. A method as in claim 1, wherein the rollback data structure is a log and the step of rolling back the executing of the critical region of the first thread includes flushing the log.

7. A method as in claim 1, further comprising the steps of comparing a priority of the first thread to a minimum priority of a synchronization tool and permitting the step of rolling back the executing of the critical region if the priority of the first thread is less than the minimum priority.

8. A method as in claim 7, wherein the synchronization tool is a lock configurable to operate in at least two modes selected from a priority inheritance protocol mode, a priority ceiling protocol mode, a boost mode and a priority rollback mode, further comprising the step of configuring the lock to operate in one of the at least the two modes based upon the priority of the first thread, the minimum priority and the maximum priority.

9. A method as in claim 1, wherein the critical region comprises a portion of the first thread protected by a synchronization tool and configured to modify the software resource.

10. A method executable with a processing device according to processing instructions embedded in a non-transitory computer readable medium to prevent concurrent access to a software resource by a first processing sequence and a second processing sequence, the method comprising:

executing the first processing sequence with the processing device;

writing rollback information to a rollback data structure based on the first processing sequence;

detecting an indication that the second processing sequence seeks access to the software resource; and

after detecting the indication, rolling back the executing of the first processing sequence.

11. A method as in claim 10, wherein rolling back the executing of the first processing sequence reduces a worst case execution time of the second processing sequence.

12. A method as in claim 10, wherein the rollback data structure is a buffer and the step of rolling back the executing of the first processing sequence includes releasing a synchronization tool without flushing the buffer.

13. A method as in claim 12, further comprising the steps of flushing the buffer and modifying a status indicator of the synchronization tool to indicate that flushing begun, wherein if flushing begun before the indication is detected in the detecting step, the second processing sequence cannot access the software resource until the flushing step is complete.

14. A method as in claim 10, wherein the rollback data structure is a log and the step of rolling back the executing of the first processing sequence includes flushing the log.

15. A method as in claim 10, further comprising the steps of comparing a priority of the first processing sequence to a minimum priority of a synchronization tool and permitting the step of rolling back the executing of the first processing sequence if the priority of the first processing sequence is less than the minimum priority.

16. A non-transitory computer-readable medium operable by a processing device to prevent concurrent access to a software resource by a first processing sequence and a second processing sequence, the non-transitory computer-readable medium comprising a plurality of processing sequences embedded therein including:

a third processing sequence configured for writing rollback information to a rollback data structure based on execution of the first processing sequence;

a fourth processing sequence configured for detecting an indication that the second processing sequence seeks access to the software resource; and

a fifth processing sequence configured for rolling back the execution of the first processing sequence after detecting the indication.

17. A computer-readable medium as in claim 16, further including a sixth processing sequence configured for controlling operation of a hardware resource based on the software resource.

18. A computer-readable medium as in claim 16, wherein rolling back the execution of the first processing sequence reduces a worst case execution time of the second processing sequence.

19. A computer-readable medium as in claim 16, wherein the rollback data structure is a buffer and rolling back the execution of the first processing sequence includes releasing a synchronization tool without flushing the buffer.

20. A computer-readable medium as in claim 16, wherein the rollback data structure is a log and rolling back the execution of the first processing sequence includes flushing the log.

21. A computer-readable medium as in claim 16, further including a sixth processing sequence configured to generate a seventh processing sequence including a portion of the first processing sequence which is protected by a synchronization tool and configured to modify the software resource, the third processing sequence, the fourth processing sequence and the fifth processing sequence.

22. A computer-readable medium as in claim 16, further including a sixth processing sequence configured to append to the first processing sequence the third processing sequence, the fourth processing sequence and the fifth processing sequence.

23. An system configured to prevent concurrent access to a software resource, the system comprising:

a support structure;

a hardware resource supported by the support structure;

a processing device supported by the support structure, the processing device adapted for executing a first processing sequence and a second processing sequence;

a non-transitory computer-readable medium supported by the support structure; and

a plurality of processing sequences embedded in the non-transitory computer-readable medium including

a third processing sequence adapted for writing rollback information to a rollback data structure based on the first processing sequence;

a fourth processing sequence configured for detecting an indication that the second processing sequence seeks access to the software resource; and

a fifth processing sequence configured for rolling back the execution of the first processing sequence after detecting the indication.

24. A system as in claim 23, further comprising a synchronization tool having a first status bit, the first status bit having a first status when the second processing sequence seeks access to the software resource and a second status otherwise.

25. A system as in claim 23, further comprising a synchronization tool having a rollback status bit, the rollback status bit having a first rollback status when the first processing sequence acquires the synchronization tool in a rollback mode and a second rollback status otherwise.

26. A system as in claim 23, further comprising a sixth processing sequence and a synchronization tool having a flushing status bit, the rollback data structure comprising a buffer, the sixth processing sequence configured to flush the buffer and to change the flushing status bit from a first flushing status to permit the rolling back to a second flushing status to prevent the rolling back.