WAKE-UP ORDERING OF PROCESSING STREAMS USING SEQUENTIAL IDENTIFIERS

• US 20160147576A1
• Filed: 11/25/2014
• Published: 05/26/2016
• Est. Priority Date: 11/25/2014
• Status: Active Grant

• Current Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Original Assignee: Red Hat, Inc. (International Business Machines Corporation)
• Inventors: Riegel, Torvald
• Granted Patent: US 10,025,642 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 9/485 Task life-cycle, e.g. stopping, restarting, resuming execution G06F9/4881 takes precedence
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

Systems and methods for waking up waiting processing streams in a manner that reduces the number of spurious wakeups. An example method may comprise: assigning a first identifier of a sequence of identifiers to a processing stream in a waiting state; receiving a wakeup signal associated with a second identifier of the sequence of identifiers; comparing, by a processing device, the first identifier with the second identifier; and waking the processing stream responsive to determining, in view of comparing, that the processing stream began waiting prior to an initiation of the wakeup signal.

Claims

1. A method comprising:

assigning a first identifier of a sequence of identifiers to a processing stream in a waiting state;

receiving a wakeup signal associated with a second identifier of the sequence of identifiers;

comparing, by a processing device, the first identifier with the second identifier; and

waking the processing stream responsive to determining, in view of comparing, that the processing stream began waiting prior to an initiation of the wakeup signal.

2. The method of claim 1, wherein the sequence reflects a chronological order of a plurality of wakeup signals and a plurality of processing streams.

3. The method of claim 1, wherein determining that the processing stream began waiting prior to initiation of the wakeup signal comprises determining that the first identifier is less than the second identifier.

4. The method of claim 1, wherein assigning the first identifier to the processing stream is performed in response to receiving a wait function call to block a processing stream.

5. The method of claim 1, wherein the wakeup signal is initiated by a wakeup function call.

6. The method of claim 1, wherein the first identifier and the second identifier are provided by condition variables.

7. The method of claim 6, further comprising resetting the first identifier responsive to determining that the value of the second identifier exceeds a threshold value, wherein the threshold value is a maximum value provided by the condition variable.

8. The method of claim 1, wherein the second identifier associated with the wakeup signal is stored in a futex data structure.

9. The method of claim 1, further comprising:

assigning a third identifier to an additional processing stream, wherein the additional processing stream initiates a wait function call after the wakeup signal is initiated but prior to the wakeup signal being received;

determining the third identifier of the additional processing stream is greater than the second identifier; and

processing the wakeup signal without waking up the additional processing stream.

10. The method of claim 9, further comprising:

grouping multiple processing streams into a plurality of groups comprising a first group and a second group, the first group comprising a processing stream initiating a first wait function call prior to the wakeup signal being initiated, and a second group comprises a second processing stream initiating a second wait function after the wakeup signal being initiated;

waking up the first processing stream in the first group without waking up the second processing stream in the second group; and

associating the second processing stream with the first group after the first processing stream consumes the wakeup signal.

11. The method of claim 10, wherein associating the second processing stream with the first group is performed after removing one or more waiting processing streams from the first group.

12. The method of claim 10, wherein the first processing streams of the first group and the second processing stream of the second group are executing on a single machine.

14. The system of claim 6, wherein the processing device further to reset the first identifier responsive to determining that the value of the second identifier exceeds a threshold value, wherein the threshold value is a maximum value provided by the condition variable.

15. The system of claim 1, wherein the processing device further to:

assign a third identifier to an additional processing stream, wherein the additional processing stream initiates a wait function call after the wakeup signal is initiated but prior to the wakeup signal being received;

determine the third identifier of the additional processing stream is greater than the second identifier; and

process the wakeup signal without waking up the additional processing stream.

16. The system of claim 9, wherein the processing device further to:

group multiple processing streams into a plurality of groups comprising a first group and a second group, the first group comprising a processing stream initiating a first wait function call prior to the wakeup signal being initiated, and a second group comprises a second processing stream initiating a second wait function after the wakeup signal being initiated;

wake up the first processing stream in the first group without waking up the second processing stream in the second group; and

associate the second processing stream with the first group after the first processing stream consumes the wakeup signal.

18. The non-transitory machine-readable storage medium of claim 6, wherein the instructions further comprising:

reset the first identifier responsive to determining that the value of the second identifier exceeds a threshold value, wherein the threshold value is provided by a maximum value for the condition variable.

19. The non-transitory machine-readable storage medium of claim 1, wherein the instructions further comprising:

assign a third identifier to an additional processing stream, wherein the additional processing stream initiates a wait function call after the wakeup signal is initiated but prior to the wakeup signal being received;

determine the third identifier of the additional processing stream is greater than the second identifier; and

process the wakeup signal without waking up the additional processing stream.

20. The non-transitory machine-readable storage medium of claim 9, wherein the instructions further comprising:

group multiple processing streams into a plurality of groups comprising a first group and a second group, the first group comprising a processing stream initiating a first wait function call prior to the wakeup signal being initiated, and a second group comprises a second processing stream initiating a second wait function after the wakeup signal being initiated;

wake up the first processing stream in the first group without waking up the second processing stream in the second group; and

associate the second processing stream with the first group after the first processing stream consumes the wakeup signal.

13. A system comprising:

a memory; and

a processing device communicably coupled to the memory, the processing device to execute instructions to;

assign a first identifier of a sequence of identifiers to a processing stream in a waiting state;

receive a wakeup signal associated with a second identifier of the sequence of identifiers;

compare, by a processing device, the first identifier with the second identifier; and

wake the processing stream responsive to determining, in view of comparing, that the processing stream began waiting prior to an initiation of the wakeup signal.

17. A non-transitory machine-readable storage medium storing instructions which, when executed, cause a processing device to execute operations comprising:

assign a first identifier of a sequence of identifiers to a processing stream in a waiting state;

receive a wakeup signal associated with a second identifier of the sequence of identifiers;

compare, by a processing device, the first identifier with the second identifier; and

wake the processing stream responsive to determining, in view of comparing, that the processing stream began waiting prior to an initiation of the wakeup signal.