Interrupt Controller Race Condition Detection via Dummy Request

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Solution Overview

Problem

Existing interrupt controllers face challenges in determining when an interrupt request has been received by a processing element, leading to potential delays or interference with processing events, especially in scenarios where the timing of acknowledgement is variable and resource-intensive operations are involved.

Innovation Solution

The implementation of an interrupt controller that detects race conditions and uses a dummy request to confirm receipt of a pending interrupt request, allowing the setting of a barrier indicator to ensure that processing events are delayed until the interrupt request is received, thereby preventing premature execution of operations that could interfere with the interrupt processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the interrupt controller waits for an acknowledgement to determine that the processing element has received the interrupt request, then the reliability of interrupt delivery is improved, but the time delay increases and processing events are delayed

Engineering Contradiction:

Improveinterrupt delivery confirmationVSAvoidprocessing event delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by sending a dummy interrupt request immediately after the actual interrupt request, before waiting for the acknowledgement. This preliminary dummy request serves as a probe to determine if the processing element is ready to receive interrupts, allowing the system to make informed decisions about subsequent interrupt delivery without waiting for the full acknowledgement cycle to complete.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy interrupt request acts as an intermediary mechanism between the actual interrupt request and the acknowledgement. It provides indirect information about the processing element's readiness state without requiring the processing element to actually process the dummy interrupt, thus reducing the time penalty while maintaining reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the interrupt controller sends multiple interrupt requests including a dummy request to ensure proper sequencing, then the reliability of interrupt handling is improved, but the device complexity increases

Engineering Contradiction:

Improveinterrupt handling correctnessVSAvoidinterrupt controller logic

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interrupt delivery process is segmented into distinct phases: sending the actual interrupt request, immediately following it with a dummy interrupt request, and then conditionally sending a barrier request based on the dummy request's outcome. This segmentation allows each phase to be independently controlled and optimized, reducing overall complexity while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The interrupt controller dynamically adjusts its behavior based on the outcome of the dummy interrupt request. If the dummy request is acknowledged, the controller knows the processing element is ready and can proceed without additional barriers. If not acknowledged, the controller inserts a barrier request. This dynamic adaptation reduces unnecessary complexity in the interrupt control logic.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If the processing element acknowledges every interrupt request, then the accuracy of receipt confirmation is improved, but the use of energy increases due to resource-intensive operations

Engineering Contradiction:

Improvereceipt confirmation accuracyVSAvoidprocessing element energy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system applies partial action by having the processing element acknowledge only the dummy interrupt request under specific conditions, rather than acknowledging every interrupt request. The dummy request serves as a minimal overhead probe that provides sufficient information about system state without requiring full interrupt processing, thus reducing energy consumption while maintaining confirmation accuracy.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The dummy interrupt request mechanism establishes a feedback loop that provides information about the processing element's readiness state without requiring energy-intensive full interrupt processing. The acknowledgement of the dummy request serves as feedback about system state, allowing the interrupt controller to make informed decisions without consuming excessive energy.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11429426B2Interrupt controller

Publication Date: 2022.08.30 ARM LTD

AI summary

An interrupt controller comprises issue circuitry to issue interrupt requests to a processing element and control circuitry to detect presence of a race condition in association with at least one pending interrupt request to be issued, and to set a barrier indicator when the race condition has been resolved. In response to the race condition being present, the issue circuitry is configured to select one of the at least one pending interrupt requests, to issue to the processing element the selected pending interrupt request followed by a dummy request over a path that ensures that the processing element receives the selected pending interrupt request prior to receiving the dummy request. On receiving an acknowledgement indicating that the processing element has received the dummy request, the control circuitry is then configured to set the barrier indicator.