Enabling Real-Time CPU-Bound In-Kernel Workloads To Run Infinite Loops While Keeping RCU Grace Periods Finite

• US 20190034231A1
• Filed: 10/04/2018
• Published: 01/31/2019
• Est. Priority Date: 12/11/2016
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McKenney, Paul E.
• Granted Patent: US 10,459,761 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 9/4887 involving deadlines, e.g. rate based, periodic
• CPC Class Codes: G06F 9/505 considering the load

Abstract

A technique for enabling real-time CPU-bound in-kernel workloads to run infinite loops while keeping read-copy update (RCU) grace periods finite. In an embodiment, a per-CPU indicator may be set to indicate that a CPU running the CPU-bound in-kernel workload has not reported an RCU quiescent state within a defined time. A function may be invoked from within the workload that causes an RCU quiescent state to be reported on behalf of the CPU if the per-CPU indicator is set. If the RCU quiescent state is not reported within a longer defined time, the CPU may be rescheduled.

Claims

1-7. -7. (canceled)

8. :

A system, comprising;

a plurality of CPUs;

a memory coupled to the CPUs, the memory including a non-transitory computer readable storage medium tangibly embodying at least one program of instructions executable by the CPUs to perform operations for enabling real-time CPU-bound in-kernel workloads to run infinite loops while keeping read-copy update (RCU) grace periods finite, the operations comprising;

setting a per-CPU indicator to indicate that a CPU running the CPU-bound in-kernel workload has not reported an RCU quiescent state within a defined time;

invoking from within the workload a function that causes an RCU quiescent state to be reported on behalf of the CPU if the per-CPU indicator is set; and

if the RCU quiescent state is not reported within a longer defined time, rescheduling the CPU.

9. :

The system of claim 8, wherein the indicator is set by an RCU grace period function that handles quiescent states on behalf of CPUs that have failed to report a quiescent state within the defined time, and which forces the CPUs to be rescheduled if a quiescent state cannot be reported within the longer defined time.

10. :

The system of claim 8, wherein the function that causes the RCU quiescent state to be reported is periodically invoked while the workload is active.

11. :

The system of claim 8, wherein the function that causes the RCU quiescent state to be reported is periodically invoked by the workload at an interval that is shorter than the longer defined time.

12. :

The system of claim 8, wherein the longer defined time is based on an RCU CPU stall warning time.

13. :

The system of claim 8, wherein the longer defined time represents a time since the beginning of a current grace period that is more than halfway to an RCU CPU stall warning time.

14. :

The system of claim 8, wherein the function that causes the RCU quiescent state to be checked invokes a flow of control that causes an RCU quiescent state to be reported due to manipulation of an RCU dyntick-idle state of the CPU.

15. :

A computer program product, comprising;

one or more non-transitory computer readable data storage media;

program instructions stored on the one or more computer readable data storage media for programming a data processing platform having a plurality of CPUs to perform operations for enabling real-time CPU-bound in-kernel workloads to run infinite loops while keeping read-copy update (RCU) grace periods finite, the operations comprising;

setting a per-CPU indicator to indicate that a CPU running the CPU-bound in-kernel workload has not reported an RCU quiescent state within a defined time;

invoking from within the workload a function that causes an RCU quiescent state to be reported on behalf of the CPU if the per-CPU indicator is set; and

if the RCU quiescent state is not reported within a longer defined time, rescheduling the CPU.

16. :

The computer program product of claim 15, wherein the indicator is set by an RCU grace period function that handles quiescent states on behalf of CPUs that have failed to report a quiescent state within the defined time, and which forces the CPUs to be rescheduled if a quiescent state cannot be reported within the longer defined time.

17. :

The computer program product of claim 15, wherein the function that causes the RCU quiescent state to be reported is periodically invoked while the workload is active.

18. :

The computer program product of claim 15, wherein the function that causes the RCU quiescent state to be reported is periodically invoked by the workload at an interval that is shorter than the longer defined time.

19. :

The computer program product of claim 15, wherein the longer defined time is based on an RCU CPU stall warning time.

20. :

The computer program product of claim 15, wherein the function that causes the RCU quiescent state to be checked invokes a flow of control that causes an RCU quiescent state to be reported due to manipulation of an RCU dyntick-idle state of the CPU.