Process.WaitForExit() hangs forever even after process exits, I don't have control over child processes

[gcampbell-msft]

Description

This is very similar to #29232. However, specifically in this case I do not have a control over whether the process creates it's subprocesses in any certain way.

This is happening on Windows for me specifically.

In my case, I'm using very simple process.start and data output and error output handlers, similar to the docs.

Reproduction Steps

Ensure that the following is set:

processStartInfo.RedirectStandardOutput = true;
processStartInfo.RedirectStandardError = true;
processStartInfo.UseShellExecute = false;
processStartInfo.CreateNoWindow = true;

And that you have dataoutput handlers and error output handlers.

Expected behavior

No hanging on the WaitForExit.

Actual behavior

Hanging on the WaitForExit

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-diagnostics-process
See info in area-owners.md if you want to be subscribed.

[gcampbell-msft]

This is also a related issue: #51277

[tmds]

.NET can't solve this.

You want to wait for all data, but grand children are keeping the pipes open. There is no way .NET can know when all data was produced.

The workaround is to call WaitForExit with timeouts. When it returns true, you should call it again with a "small" timeout so you deplete any data that is still left in the pipe when the direct child exited.