[17.14] Avoid hang when similar build requests are serviced #12197
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Pull Request Overview
This backport addresses a MSBuild scheduler hang issue when two similar-but-not-identical build requests are serviced in close proximity. The fix prevents Visual Studio from hanging by properly handling cases where cached results cannot satisfy duplicate requests, and adds diagnostic fields to improve future debugging.
- Fixes the scheduler hang by allowing unscheduled requests to remain in the queue for proper rebuilding instead of incomplete handling
- Adds diagnostic fields
_hitNoLoggingCompletedand_noLoggingCompletedSubmissionDetailsfor memory dump analysis - Includes comprehensive unit tests covering both cache hit and cache miss scenarios for duplicate requests
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/Build/BackEnd/Components/Scheduler/Scheduler.cs | Core fix for the hang issue with diagnostic breadcrumbs and improved error handling |
| src/Build/BackEnd/BuildManager/BuildManager.cs | Minor variable rename for clarity (response → responses) |
| src/Build.UnitTests/BackEnd/Scheduler_Tests.cs | Test infrastructure improvements and two new comprehensive tests for the fix |
| eng/Versions.props | Version bump from 17.14.16 to 17.14.17 with formatting issue |
YuliiaKovalova
approved these changes
Jul 21, 2025
baronfel
approved these changes
Jul 22, 2025
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Backports #11862 to 17.14.
Work item (Internal use): devdiv2530919
Summary
The MSBuild scheduler could hang when two similar-but-not-identical requests were received and serviced in short proximity. VS calling patterns trigger this sometimes.
This change handles the problematic case and additionally provides breadcrumbs in the memory dump that this situation occurred to improve future diagnosability of related issues.
Customer Impact
VS hang observed from telemetry; VS Perf team wants backport.
Regression?
No
Testing
Has been in main (.NET SDK 10 builds) and internal VS preview for ~1 month, with good telemetry from VS int preview.
Risk
Low due to bake time in main/int preview.