dotnet/msbuild

[Unhandled Exception]: Unable to set thread priority

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#12,677 opened on Oct 20, 2025

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help wantedtriaged

Description

Issue Description

dotnet restore fails with:

MSBUILD : error :
  This is an unhandled exception in MSBuild -- PLEASE UPVOTE AN EXISTING ISSUE OR
  FILE A NEW ONE AT https://aka.ms/msbuild/unhandled
      System.Threading.ThreadStateException: Unable to set thread priority.
     at System.Threading.Thread.SetPriorityNative(Int32 priority)
     at System.Threading.Thread.set_Priority(ThreadPriority value)
     at Microsoft.Build.BackEnd.RequestBuilder.SetCommonWorkerThreadParameters()
     at Microsoft.Build.BackEnd.RequestBuilder.RequestThreadProc(Boolean setThread
  Parameters)

Restore failed with 1 error(s) in 2.2s

when running on Android via Nix-on-droid

Steps to Reproduce

  1. Install the dotnet sdk on an Android phone via Nix-on-droid
  • Will most probably require setting DOTNET_GCHeapHardLimit environment variable to 1C0000000
  1. Create a new project via dotnet new console
  2. Run dotnet restore

Actual Behavior

  • Result of step 1: project files are created, restore fails
  • Result of step 2: restore fails with the above message

Analysis

No response

Versions & Configurations

$ dotnet msbuild --version
17.15.0.35903

$ dotnet --version
10.0.100-preview.6.25358.103

Contributor guide

Tech stack
csharp
Domain
build system
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C#MSBuild internalsAndroid threading
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the stack trace in Microsoft.Build.BackEnd.RequestBuilder.SetCommonWorkerThreadParameters and RequestThreadProc. Determine why Thread.SetPriority fails on Android under Nix on droid. Consider adding a try catch to handle ThreadStateException gracefully or check platform support before setting priority. Look at the MSBuild codebase for similar thread priority handling patterns.