Process crash when System.Diagnostics.Process can't find child process

[BrennanConroy]

We saw a test run crash recently with the error below. I would hope crashing the process is not the desired behavior here.

Process terminated.
Error while reaping child. errno = 10
    at System.Environment.FailFast(System.Runtime.CompilerServices.StackCrawlMarkHandle, System.String, System.Runtime.CompilerServices.ObjectHandleOnStack, System.String)
    at System.Environment.FailFast(System.Threading.StackCrawlMark ByRef, System.String, System.Exception, System.String)
    at System.Environment.FailFast(System.String)
    at System.Diagnostics.ProcessWaitState.TryReapChild(Boolean)
    at System.Diagnostics.ProcessWaitState.CheckChildren(Boolean, Boolean)
    at System.Diagnostics.Process.OnSigChild(Int32, Int32)

Crash dumps and logs available at https://dev.azure.com/dnceng-public/public/_build/results?buildId=1060264&view=ms.vss-test-web.build-test-results-tab&runId=28602304&resultId=124848&paneView=dotnet-dnceng.dnceng-build-release-tasks.helix-test-information-tab (although the crash dump is for the code using System.Diagnostics.Process not the process it failed to find)

cc @tmds

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[tmds]

The crashing is intentional, see #70705 (comment).

Unfortunately, the crashdump doesn't help to find the cause. It happens when .NET finds out something else (in the process) reapt its child process.

Does the app that crashes use some native libraries? Can you reproduce the issue?

[BrennanConroy]

The app is the test host. I don't know what it does, or what process it launched and failed to find.
It's a random test failure on helix, haven't seen it again yet, but will keep my eyes out.