`!PreemptiveGCDisabled` assert failure from `FiberDetachCallback` during System.Runtime.Tests on win-arm64

[jakobbotsch]

We see this failure relatively consistently in libraries-jitstress pipeline, but it happens even in the legs without jitstress.

Example pipeline run: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1166315&view=results
Example test failure: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1166315&view=ms.vss-test-web.build-test-results-tab&runId=32268716&resultId=212753&paneView=debug
Example console log: https://helixr18s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-heads-main-00cfbd78498c453ba0/System.Runtime.Tests/1/console.19e7683a.log

set DOTNET_TieredCompilation=0
set DOTNET_JITMinOpts=1
...
C:\h\w\B1A7099C\w\A9560970\e>"C:\h\w\B1A7099C\p\dotnet.exe" exec --runtimeconfig System.Runtime.Tests.runtimeconfig.json --depsfile System.Runtime.Tests.deps.json xunit.console.dll System.Runtime.Tests.dll -xml testResults.xml -nologo -nocolor -notrait category=AdditionalTimezoneChecks -notrait category=IgnoreForCI -notrait category=OuterLoop -notrait category=failing  
  Discovering: System.Runtime.Tests (method display = ClassAndMethod, method display options = None)
  Discovered:  System.Runtime.Tests (found 9507 of 9556 test cases)
  Starting:    System.Runtime.Tests (parallel test collections = on [2 threads], stop on fail = off)
    System.Tests.DateTimeOffsetTests.ToLocalTime_MaxValue [SKIP]
      Condition(s) not met: "IsMaxValuePositiveLocalOffset"
    System.Tests.DateTimeOffsetTests.ToLocalTime_MinValue [SKIP]
      Condition(s) not met: "IsMinValueNegativeLocalOffset"
    System.Tests.DateTimeOffsetTests.ToLocalTime_Ambiguous [SKIP]
      Condition(s) not met: "IsPacificTime"
    System.Tests.ArgIteratorTests.ArgIterator_Throws_PlatformNotSupportedException [SKIP]
      Condition(s) not met: "IsArgIteratorNotSupported"
    System.Tests.UIntPtrTests.BigMul32 [SKIP]
      Condition(s) not met: "Is32Bit"
    System.Tests.TimeZoneInfoTests.UnsupportedImplicitConversionTest [SKIP]
      Condition(s) not met: "DoesNotSupportIanaNamesConversion"

Assert failure(PID 13100 [0x0000332c], Thread: 13380 [0x3444]): !PreemptiveGCDisabled()

CORECLR! Thread::DetachThread + 0x140 (0x00007ffc`8b575b28)
CORECLR! FiberDetachCallback + 0xE0 (0x00007ffc`8b7ee800)
NTDLL! RtlPcToFileHeader + 0x628 (0x00007ffc`fa513e48)
<no module>! <no symbol> + 0x0 (0x4d63fffc`fa58d3a8)
    File: D:\a\_work\1\s\src\coreclr\vm\threads.cpp:908
    Image: C:\h\w\B1A7099C\p\dotnet.exe

----- end Mon 10/06/2025  8:20:43.93 ----- exit code -1073740286 ----------------------------------------------------------
----- start ===============  XUnitLogChecker Output =====================================================

Known Issue Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["!PreemptiveGCDisabled()", "Thread::DetachThread", "FiberDetachCallback"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1166315
Error message validated: [!PreemptiveGCDisabled() Thread::DetachThread FiberDetachCallback]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 10/6/2025 12:08:06 PM UTC

Report

Build	Definition	Test	Pull Request
1166315	dotnet/runtime	System.Runtime.Tests.WorkItemExecution

Summary

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

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[MihuBot]

I'm a bot. Here are possible related and/or duplicate issues (I may be wrong):

• Assert failure: Consistency check failed: FAILED: pThread->PreemptiveGCDisabled() #114638
• Assert failure: pThread->PreemptiveGCDisabled #116840

[jkotas]

We are hitting UNREACHABLE() at:

13 0000000a`c3cf7f40 00007ffc`8b740cbc     coreclr!_wassert+0x34 [minkernel\crts\ucrt\src\appcrt\startup\assert.cpp @ 443] 
14 0000000a`c3cf7f70 00007ffc`8b740f40     coreclr!DispatchExSecondPass+0x184 [D:\a\_work\1\s\src\coreclr\vm\exceptionhandling.cpp @ 4346] 
15 0000000a`c3cf7fe0 00007ffc`8b7462bc     coreclr!DispatchManagedException+0x240 [D:\a\_work\1\s\src\coreclr\vm\exceptionhandling.cpp @ 1605] 
16 0000000a`c3cf9100 00007ffc`fa634b04     coreclr!ProcessCLRException+0x18c [D:\a\_work\1\s\src\coreclr\vm\exceptionhandling.cpp @ 658] 
17 0000000a`c3cf9150 00007ffc`fa5161e8     ntdll!RtlpExecuteHandlerForUnwind+0x14 [minkernel\ntos\rtl\arm64\xcptmisc.asm @ 276] 
18 0000000a`c3cf9170 00007ffc`fa515d40     ntdll!RtlUnwindEx+0x468 [minkernel\ntos\rtl\arm64\exdsptch.c @ 1414] 
19 0000000a`c3cf97c0 00007ffc`8b7407bc     ntdll!RtlUnwind+0x20 [minkernel\ntos\rtl\arm64\exdsptch.c @ 1034] 
1a 0000000a`c3cf9b70 00007ffc`8b746294     coreclr!ClrUnwindEx+0x2c [D:\a\_work\1\s\src\coreclr\vm\exceptionhandling.cpp @ 1689] 
1b 0000000a`c3cf9b80 00007ffc`fa634ae4     coreclr!ProcessCLRException+0x164 [D:\a\_work\1\s\src\coreclr\vm\exceptionhandling.cpp @ 657] 
1c 0000000a`c3cf9bd0 00007ffc`fa515708     ntdll!RtlpExecuteHandlerForException+0x14 [minkernel\ntos\rtl\arm64\xcptmisc.asm @ 142] 
1d 0000000a`c3cf9bf0 00007ffc`fa513574     ntdll!RtlDispatchException+0x2e8 [minkernel\ntos\rtl\arm64\exdsptch.c @ 725] 
1e 0000000a`c3cfa230 00007ffc`f5b78d14     ntdll!RtlRaiseException+0xf4 [minkernel\ntos\rtl\arm64\raise.c @ 127] 
1f 0000000a`c3cfa710 00007ffc`8b4b8604     KERNELBASE!RaiseException+0x74 [minkernel\kernelbase\xcpt.c @ 954] 
20 0000000a`c3cfa7c0 00007ffc`8b4b643c     coreclr!`RaiseTheExceptionInternalOnly'::`50'::__Body::Run+0x304 [D:\a\_work\1\s\src\coreclr\vm\excep.cpp @ 2406] 
21 0000000a`c3cfa850 00007ffc`8b6c6148     coreclr!RaiseTheExceptionInternalOnly+0x1ec [D:\a\_work\1\s\src\coreclr\vm\excep.cpp @ 2408] 
22 0000000a`c3cfa960 00007ffc`8b6c5e5c     coreclr!Thread::HandleThreadAbort+0x1b8 [D:\a\_work\1\s\src\coreclr\vm\threadsuspend.cpp @ 2307] 
23 0000000a`c3cfa9e0 00007ffc`8b6c4d68     coreclr!HandleSuspensionForInterruptedThread+0x23c [D:\a\_work\1\s\src\coreclr\vm\threadsuspend.cpp @ 5821] 
24 0000000a`c3cfb490 00007ffc`8b2e1de8     coreclr!Thread::ApcActivationCallback+0xc0 [D:\a\_work\1\s\src\coreclr\vm\threadsuspend.cpp @ 5906] 
25 0000000a`c3cfb4c0 00007ffc`fa5a4408     coreclr!ApcActivationCallbackStub+0x18 [D:\a\_work\1\s\artifacts\obj\coreclr\windows.arm64.Checked\vm\wks\asmhelpers.asm @ 6866] 
26 0000000a`c3cfb4e0 00007ffc`fa634838     ntdll!RtlDispatchAPC+0x68 [minkernel\ldr\rtlstrt.c @ 1019] 
27 0000000a`c3cfb570 00007ffc`314acc10     ntdll!KiUserApcDispatcher+0x38 [minkernel\ntos\rtl\arm64\trampoln.asm @ 460]