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

Patent metadata

Field	Value
Publication number	US-10229075-B2
Application number	US-201715824545-A
Country	US
Kind code	B2
Filing date	Nov 28, 2017
Priority date	Nov 16, 2015
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

Abstract

A method of handling interrupts includes receiving an event notification message (ENM) that specifies a level, an event target number (ETN), and a number of bits to ignore. A group of virtual processor threads that may be potentially interrupted are determined based on the ETN, the number of bits to ignore, and a process identifier when the level specified in the ENM corresponds to a user level. The ETN identifies a specific virtual processor thread and the number of bits to ignore identifies the number of lower-order bits to ignore when determining a group of virtual processor threads that may be potentially interrupted. In response to no virtual processor thread within the group of virtual processor threads being dispatched and operating on an associated physical processor, an escalate message that includes an escalate event number is transmitted. The escalate event number is used to generate a subsequent ENM.

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 non-zero 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 a group of virtual processor threads that may be potentially interrupted;
determining whether virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor;
in response to determining multiple virtual processor threads within the group of virtual processor threads are 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; and
in response to no virtual processor thread within the group of virtual processor threads being dispatched and operating on an associated physical processor, transmitting, by the IPC, an escalate message, wherein the escalate message includes an escalate event number that is used by an interrupt source controller (ISC) to generate a subsequent ENM.

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 1 , the method further comprising:
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.

4. The method of claim 1 , 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.

5. The method of claim 1 , wherein the method further comprises:
in response to determining that all of multiple virtual processor threads within the group that are dispatched and operating on an associated physical processor 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.

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

7. The method of claim 4 , 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.

8. The method of claim 5 , 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.

9. The method of claim 5 , 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.

10. The method of claim 9 , 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.

11. 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 non-zero 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 a group of virtual processor threads that may be potentially interrupted;
determine whether virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor;
in response to determining multiple virtual processor threads within the group of virtual processor threads are dispatched and operating on an associated physical processor, select one of the multiple virtual processor threads to interrupt that does not already have a pending interrupt; and
in response to no virtual processor thread within the group of virtual processor threads being dispatched and operating on an associated physical processor, transmit an escalate message, wherein the escalate message includes an escalate event number that is used by the ISC to generate a subsequent ENM.

12. The processing unit of claim 11 , wherein the IPC is further configured to:
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.

13. The processing unit of claim 11 , wherein the the IPC is further configured to:
in response to more than one of the multiple virtual processor threads not already having a pending interrupt, select one of the multiple virtual processor threads to interrupt that does not already have a pending interrupt based on secondary selection criteria.

14. The processing unit of claim 11 , wherein the IPC is further configured to:
in response to determining that all of multiple virtual processor threads within the group that are dispatched and operating on an associated physical processor 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, issue a reject message to a notification source designated by an event source number specified in the ENM.

15. The processing unit of

Assignees

• IBM

Inventors

• Arndt Richard L
• Auernhammer Florian A

Classifications

• G06F9/4812 Primary

  by interrupt, e.g. masked · CPC title

• G06F13/4068

  Electrical coupling · CPC title

• G06F2212/70

  Details relating to dynamic memory management · CPC title

• G06F13/28

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

• G06F13/24

  using interrupt (G06F13/32 takes precedence) · CPC title