Techniques for handling interrupts in a processing unit using virtual processor thread groups and software stack levels

Patent metadata

Field	Value
Publication number	US-9852091-B2
Application number	US-201615334857-A
Country	US
Kind code	B2
Filing date	Oct 26, 2016
Priority date	Nov 16, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

A technique for handling interrupts in a data processing system includes receiving, at an interrupt presentation controller (IPC), an event notification message (ENM). The ENM specifies a level, an event target number, and a number of bits to ignore. The IPC determines a group of virtual processor threads that may be potentially interrupted based on the event target number, the number of bits to ignore, and a process identifier (ID) when the level specified in the ENM corresponds to a user level. The event target number identifies a specific virtual processor thread and the number of bits to ignore identifies the number of lower-order bits to ignore with respect to the specific virtual processor thread when determining a group of virtual processor threads that may be potentially interrupted.

First claim

What is claimed is:

1. A method of handling interrupts in a data processing system, the method comprising:
receiving, at an interrupt presentation controller (IPC), an event notification message (ENM), wherein the ENM specifies a level, an event target number, and a number of bits to ignore;
determining, by the IPC, a group of virtual processor threads that may be potentially interrupted based on the event target number, the number of bits to ignore, and a process identifier (ID) when the level specified in the ENM corresponds to a user level, wherein the event target number identifies a specific virtual processor thread and the number of bits to ignore identifies the number of lower-order bits to ignore with respect to the specific virtual processor thread when determining the group of virtual processor threads that may be potentially interrupted; and
in response to one or more virtual processor threads in the group of virtual processor threads being available to service an interrupt associated with the ENM, selecting a single virtual processor thread from the one or more virtual processor threads to service the interrupt.

2. The method of claim 1 , wherein the process ID is not used when the level corresponds to an operating system (OS) level.

3. The method of claim 2 , wherein the process ID is not used when the level corresponds to a hypervisor level.

4. The method of claim 1 , wherein the number of bits to ignore is ‘n’ bits and the specific virtual processor thread and (2 n −1) other virtual processor threads may be potentially interrupted.

5. The method of claim 1 , wherein the number of bits to ignore is not equal to zero and the method further comprises:
determining whether one or more virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor; and
in response to no virtual processor thread within the group of virtual processor threads being dispatched and operating on an associated physical processor, issuing a reject message to a notification source designated by an event source number specified in the ENM.

6. The method of claim 1 , wherein the number of bits to ignore is not equal to zero and the method further comprises:
determining whether multiple virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor; and
in response to the multiple virtual processor threads within the group of virtual processor threads being dispatched and operating on an associated physical processor, selecting one of the multiple virtual processor threads to interrupt that does not already have a pending interrupt.

7. The method of claim 6 , further comprising:
in response to more than one of the multiple virtual processor threads not already having a pending interrupt, selecting one of the multiple virtual processor threads to interrupt that does not already have a pending interrupt based on secondary selection criteria.

8. The method of claim 7 , wherein the secondary selection criteria includes one or more of an event priority, specified in the ENM, relative to an operating priority for each of the multiple virtual processor threads, a least recently used (LRU) one of the multiple virtual processor threads, and a random one of the multiple virtual processor threads.

9. The method of claim 1 , wherein the number of bits to ignore is not equal to zero and the method further comprises:
determining whether multiple virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor;
in response to the multiple virtual processor threads within the group of virtual processor threads being dispatched and operating on an associated physical processor, determining whether all of the multiple virtual processor threads have pending interrupts;
in response to determining that all of the multiple virtual processor threads have pending interrupts, determining whether an event priority specified in the ENM is greater than an operating priority of any of the multiple virtual processor threads; and
in response to determining that the event priority is not greater than the operating priority of any of the multiple virtual processor threads, issuing a reject message to a notification source designated by an event source number specified in the ENM.

10. The method of claim 9 , further comprising:
in response to determining that the event priority is greater than the operating priority of any of the multiple virtual processor threads, selecting one of the multiple virtual processor threads to interrupt with the operating priority less than the event priority.

11. The method of claim 9 , further comprising:
in response to determining that the event priority is greater than the operating priority of more than one of the multiple virtual processor threads, selecting one of the multiple virtual processor threads to interrupt with the operating priority less than the event priority based on secondary selection criteria.

12. The method of claim 11 , wherein the secondary selection criteria includes one or more of the event priority relative to the operating priority for the multiple virtual processor threads, a least recently used (LRU) one of the multiple virtual processor threads, and a random one of the multiple virtual processor threads.

13. A processing unit for a multithreaded data processing system, the processing unit comprising:
an interrupt source controller (ISC); and
an interrupt presentation controller (IPC) coupled to the ISC, wherein the IPC is configured to:
receive an event notification message (ENM) from the ISC, wherein the ENM specifies a level, an event target number, and a number of bits to ignore;
determine a group of virtual processor threads that may be potentially interrupted based on the event target number, the number of bits to ignore, and a process identifier (ID) when the level specified in the ENM corresponds to a user level, wherein the event target number identifies a specific virtual processor thread and the number of bits to ignore identifies the number of lower-order bits to ignore with respect to the specific virtual processor thread when determining the group of virtual processor threads that may be potentially interrupted; and
in response to one or more virtual processor threads in the group of virtual processor threads being available to service an interrupt associated with the ENM, select a single virtual processor thread from the one or more virtual processor threads to service the interrupt.

14. The processing unit of claim 13 , wherein the number of bits to ignore is not equal to zero and the IPC is further configured to:
determine whether one or more virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor; and
in response to no virtual processor thread within the group of virtual processor threads being dispatched and operating on an associated physical processor, issue a reject message to a notification source designated by an event source number specified in the ENM.

15. The processing unit of claim 13 , wherein the number of bits to ignore is not equal to zero and the IPC is further configured to:
determine whether multiple virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor; and
in response to the multiple virtual processor threads within the group of virtual processor threads being dispatched

Assignees

• IBM

Inventors

• Arndt Richard L
• Auernhammer Florian A

Classifications

• G06F9/4812 Primary

  by interrupt, e.g. masked · CPC title

• G06F13/28

  using burst mode transfer, e.g. direct memory access {DMA}, cycle steal (G06F13/32 takes precedence) · CPC title

• G06F9/542

  Event management; Broadcasting; Multicasting; Notifications · CPC title

• G06F13/4068

  Electrical coupling · CPC title

• G06F12/122

  of the least frequently used [LFU] type, e.g. with individual count value · CPC title