Semaphore Wait Interception for Thread Hang Anti-Pattern Detection

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Solution Overview

Problem

Detecting thread-related performance issues such as priority inversions and non-UI work on the main thread is difficult during software development, leading to potential hangs and degrading the user experience, which are often not identified until after application release.

Innovation Solution

Implementing a dynamic library in an integrated development environment (IDE) that intercepts semaphore calls to identify priority inversions and non-UI work on the main thread, flagging potential responsiveness issues and providing annotated source code to developers for optimization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If thread activity is increased to improve functionality, then application features are enhanced, but the risk of hangs and freezes increases

Engineering Contradiction:

Improveapplication functionalityVSAvoidresponse time

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary detection of priority inversion conditions by monitoring thread wait relationships before actual hangs occur. The anti-pattern detection mechanism proactively identifies situations where a high-priority thread is waiting for a low-priority thread, allowing developers to resolve issues before they manifest as freezes during normal operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback mechanisms through crash reporting systems and analytics that monitor application behavior and provide insights into thread-related issues. This feedback loop allows the system to detect patterns, report to developers, and enable iterative improvements to thread management code.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If comprehensive thread monitoring is implemented to detect all performance issues, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improveissue detection accuracyVSAvoidmonitoring system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of implementing comprehensive monitoring of all thread operations, the system focuses local quality on detecting specific anti-patterns known to cause hangs, such as priority inversions. The monitoring mechanism selectively observes critical wait relationships and thread priority interactions rather than attempting to track every thread operation, reducing complexity while maintaining detection accuracy for harmful patterns.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent extracts and isolates the critical detection function into a separate anti-pattern detection mechanism that operates independently from the main thread execution flow. This extraction allows comprehensive monitoring of priority inversion conditions without embedding complex monitoring logic throughout the entire application, thereby reducing overall system complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Loss of time

If post-release detection methods are used to identify performance issues, then development time is reduced, but the ability to optimize during development is lost

Engineering Contradiction:

Improvedevelopment timeVSAvoidissue detection timing

Core Design Contradiction:

Loss of timeVSDifficulty of detecting and measuring

Solution Approach 1:

The system enables preliminary detection of thread-related anti-patterns during the development phase through integrated monitoring tools and crash reporting mechanisms. Developers can identify priority inversion conditions and other harmful thread interactions before releasing the application, allowing for optimization during development rather than after deployment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary crash reporting system and analytics platform that bridges the gap between development and production environments. This intermediary layer collects performance data, detects anti-patterns, and provides feedback to developers during the development cycle, eliminating the need to wait until post-release to identify issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12517755B2Runtime techniques for detecting anti-patterns causing performance issues

Publication Date: 2026.01.06 APPLE INC

AI summary

Techniques may include launching an application and inserting a dynamic library into the application. An intercept wait function can intercept a target thread's call for a semaphore wait function. The semaphore wait function may request adding the target thread to a wait queue. The wait list of a table may be checked for the target thread. The table can store entries in the wait list or a signal list where an entry may include a quality-of-service category and a hang flag for a thread. The entry representing the target thread may be created after determining that the entry is not in the wait list. The semaphore wait function can enqueue the target thread to the wait queue. The target thread can be compared to entries in the signal list. The hang flag for the entry representing the target thread can be updated based on the comparison.