Test failure: System.Linq.AsyncEnumerable.Tests

[VincentBu]

Failed in: runtime-coreclr libraries-jitstress 20260701.1

Failed tests:

net11.0-windows-Release-x86-jitstress1-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_tiered-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress1_tiered-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-linux-Release-x64-jitstress2-AzureLinux.3.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x64-jitstress1-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-arm64-jitstress2-Windows.11.Arm64.Open
- System.Linq.AsyncEnumerable.Tests Work Item

Error message:

Assertion failed.
The runtime should have initialized the thread id by now.

Stack trace:

   at System.Linq.Tests.MaxByAsyncTests.VariousValues_MatchesEnumerable(Int32[] values) in /_/src/libraries/System.Linq.AsyncEnumerable/tests/MaxByAsyncTests.cs:line 52
   at System.Runtime.CompilerServices.AsyncHelpers.RuntimeAsyncTask`1.ExecuteDirectly(Thread threadPoolThread) in /_/src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.CoreCLR.cs:line 738
   at System.Runtime.CompilerServices.RuntimeAsyncTaskContinuation.Execute(Boolean canInline) in /_/src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeAsyncTaskContinuation.cs:line 35
   at System.Threading.Tasks.Task.RunContinuations(Object continuationObject) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:line 3632
   at System.Threading.Tasks.Task.FinishContinuations() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:line 3606
   at System.Threading.Tasks.Task`1.TrySetResult(TResult result) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task_T.cs:line 385
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.SetExistingTaskResult(Task`1 task, TResult result) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 524
   at System.Runtime.CompilerServices.AsyncValueTaskMethodBuilder`1.SetResult(TResult result) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncValueTaskMethodBuilderT.cs:line 54
   at System.Linq.AsyncEnumerable.<MaxByAsync>g__Impl|117_0[TSource,TKey](IAsyncEnumerable`1 source, Func`3 keySelector, IComparer`1 comparer, CancellationToken cancellationToken) in /_/src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/MaxByAsync.cs:line 230
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.ExecutionContextCallback(Object s) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 292
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs:line 196
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 371
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext() in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 350
   at System.Threading.ThreadPool.<>c.<.cctor>b__57_0(Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPoolWorkQueue.cs:line 1428
   at System.Threading.Tasks.Sources.ManualResetValueTaskSourceCore`1.SignalCompletion() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Sources/ManualResetValueTaskSourceCore.cs:line 249
   at System.Linq.AsyncEnumerable.<Select>g__Impl|148_0[TSource,TResult](IAsyncEnumerable`1 source, Func`2 selector, CancellationToken cancellationToken)+MoveNext() in /_/src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Select.cs:line 45
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.ExecutionContextCallback(Object s) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 290
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs:line 196
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 356
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext() in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 350
   at System.Threading.ThreadPool.<>c.<.cctor>b__57_0(Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPoolWorkQueue.cs:line 1428
   at System.Threading.Tasks.Sources.ManualResetValueTaskSourceCore`1.SignalCompletion() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Sources/ManualResetValueTaskSourceCore.cs:line 249
   at System.Linq.Tests.AsyncEnumerableTestExtensions.Yield[T](IAsyncEnumerable`1 source, CancellationToken cancellationToken)+MoveNext() in /_/src/libraries/System.Linq.AsyncEnumerable/tests/AsyncEnumerableTests.cs:line 104
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.ExecutionContextCallback(Object s) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 290
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs:line 196
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread) in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 356
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext() in /_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs:line 350
   at System.Linq.Tests.AsyncEnumerableTestExtensions.ForceYieldingAwaiter.<>c.<OnCompleted>b__3_0(Object s) in /_/src/libraries/System.Linq.AsyncEnumerable/tests/AsyncEnumerableTests.cs:line 110
   at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPoolWorkQueue.cs:line 1330
   at System.Threading.ThreadPoolWorkQueue.Dispatch() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPoolWorkQueue.cs:line 960
   at System.Threading.PortableThreadPool.WorkerThread.WorkerDoWork(PortableThreadPool threadPoolInstance) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/PortableThreadPool.WorkerThread.cs:line 137
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart() in /_/src/libraries/System.Private.CoreLib/src/System/Threading/PortableThreadPool.WorkerThread.cs:line 110
   at System.Threading.Thread.StartCallback(Thread* pThread) in /_/src/coreclr/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs:line 117

Note

The KBE additions below were prepared with AI/Copilot assistance.

Build Information

Build: runtime-coreclr libraries-jitstress 20260701.1
Build error leg or test failing: net11.0-linux-Release-x64-jitstress2-AzureLinux.3.Amd64.Open - System.Linq.AsyncEnumerable.Tests Work Item

Error Details

Representative confirmed failure excerpt from the preserved failure logs:

Assertion failed.
The runtime should have initialized the thread id by now.
   at System.Linq.Tests.ToHashSetAsyncTests.VariousValues_MatchesEnumerable(Int32[] values) in /_/src/libraries/System.Linq.AsyncEnumerable/tests/ToHashSetAsyncTests.cs:line 28

Error Message

{
  "ErrorMessage": "The runtime should have initialized the thread id by now.",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Failure Logs

• 1487310 source linux-x64
• 1489260 follow-up linux-x64
• 1487310 source win-x86 job 4541600b
• 1487310 source win-x86 job fbf1e34c

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1489260
Error message validated: [The runtime should have initialized the thread id by now.]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 7/3/2026 12:30:50 PM UTC

Report

Build	Repository	Test	Pull Request
1505567	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1505119	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1505020	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1504741	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1504679	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1504534	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1504504	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1502812	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1500785	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1500203	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1500199	dotnet/runtime	System.Threading.Tasks.Dataflow.Tests.WorkItemExecution
1494534	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1500201	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1500200	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494056	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1498655	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1496513	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494990	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494363	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494188	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494160	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1494037	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution
1489260	dotnet/runtime	System.Linq.AsyncEnumerable.Tests.WorkItemExecution

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	16	23

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @VSadov
See info in area-owners.md if you want to be subscribed.

[VSadov]

Nothing special in the stack.
It is a threadpool thread and the thread ID should be set and likely even used a few times by the time we get to the point of failure.

Possibly a JIT issue with reading the threadID threadstatic?

Let's see if reproduces again.

[vitek-karas]

Note

The timeline summary below was prepared with AI/Copilot assistance.

Timeline from the daily runtime-coreclr libraries-jitstress runs:

• Last run I checked that did not hit this issue: 20260629.1 (build 1485400), source version 0d3df07c6048d8cbe4f544227462cae62040e587
• First run I found that did hit it: 20260630.1 (build 1487310), source version 811a5bf521e246d3ced9fba3fa36cdc342112f69
• It then reproduced again in:
  • 20260701.1 (build 1489260), source version a31b4923d5b3cc51681c997b7c4834960cc5337a
  • 20260702.1 (build 1491202), source version 8fe2929f5e365d262ca514854330c979fe6ab28b
  • 20260703.1 (build 1492849), source version 6585d1cf126b41c0554dedaa0b6fce955cdb8825

So the regression window looks to be:

• last known non-hit: 0d3df07c6048d8cbe4f544227462cae62040e587
• first known hit: 811a5bf521e246d3ced9fba3fa36cdc342112f69

This does not look like a deterministic failure on every leg. It has been consistently present at the daily-build level since 2026-06-30, but the failing legs vary by day. The most consistent signal I found was windows-x86, while linux-x64, windows-x64, and windows-arm64 appear only on some runs.

The strongest suspect in that window is PR #129954 / commit 761041faa4f (coreclr: implement Environment.CurrentManagedThreadId via ManagedThreadId.Current). That change is directly in the area implicated by the assert and by the observed stacks, since it changed managed thread ID access from the native helper path to a thread-static read.

[VincentBu]

Failed in: runtime-coreclr libraries-jitstress2-jitstressregs 20260704.1

Failed tests:

net11.0-windows-Release-x86-jitstress2_jitstressregs1-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_jitstressregs2-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_jitstressregs4-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_jitstressregs8-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_jitstressregs0x2000-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x86-jitstress2_jitstressregs0x1000-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x64-jitstress2_jitstressregs1-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x64-jitstress2_jitstressregs8-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x64-jitstress2_jitstressregs0x10-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-x64-jitstress2_jitstressregs3-Windows.10.Amd64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-arm64-jitstress2_jitstressregs1-Windows.11.Arm64.Open
- System.Linq.AsyncEnumerable.Tests Work Item
net11.0-windows-Release-arm64-jitstress2_jitstressregs3-Windows.11.Arm64.Open
- System.Linq.AsyncEnumerable.Tests Work Item

Error message:

Assertion failed.
The runtime should have initialized the thread id by now.
   at System.Linq.Tests.ToHashSetAsyncTests.VariousValues_MatchesEnumerable(Int32[] values) in /_/src/libraries/System.Linq.AsyncEnumerable/tests/ToHashSetAsyncTests.cs:line 28
   at Xunit.Sdk.AsyncTestSyncContext.<>c__DisplayClass7_0.<Post>b__0() in /_/src/xunit.execution/Sdk/AsyncTestSyncContext.cs:line 58
   at Xunit.Sdk.XunitWorkerThread.<>c.<QueueUserWorkItem>b__5_0(Object _) in /_/src/common/XunitWorkerThread.cs:line 37
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs:line 196
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread) in /_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs:line 2492
   at System.Threading.Thread.StartCallback(Thread* pThread) in /_/src/coreclr/System.Private.CoreLib/src/System/Threading/Thread.CoreCLR.cs:line 117
----- end Sat 07/04/2026 10:47:06.72 ----- exit code -2146232797 ----------------------------------------------------------