Assertion failure g_flsIndex != FLS_OUT_OF_INDEXES

[AndyAyersMS]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1012520
Build error leg or test failing: tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd
Pull request: #114464

Error Message

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

{
  "ErrorMessage": "g_flsIndex != FLS_OUT_OF_INDEXES",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1012520
Error message validated: [g_flsIndex != FLS_OUT_OF_INDEXES]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 4/10/2025 10:23:45 PM UTC

Report

Build	Definition	Test	Pull Request
1027292	dotnet/runtime	tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd
1021596	dotnet/runtime	tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd	#114853
1019634	dotnet/runtime	tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd	#110472
1017655	dotnet/runtime	tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd	#114585
1012520	dotnet/runtime	tracing/eventpipe/diagnosticport/diagnosticport/diagnosticport.cmd	#114464

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	1	5

[jkotas]

g_flsIndex != FLS_OUT_OF_INDEXES

cc @VSadov

[VSadov]

That is in Detach thread. Perhaps it was never attached, but then it is strange that we are detaching. I'll take a look. Maybe just assert is too restrictive.

[VSadov]

Also since it is from ep_rt_thread_coreclr_start_func, so it could be some corner case related to event pipe and thus is why we do not see this often.

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[VSadov]

got couple more counts, so this is not a one-off case.