Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it? We should probably add a test using the code samples in the issue to verify that this is sufficient to resolve it. Since the user reporting it mentioned that it was a bit intermittent, we should repeat their test a few times in our own tests.

Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it?

A root of the issue was that second thread read the HashSet while first thread still initializes the HashSet.
The HashSet is used only in one place for reading so no need to concern more about race conditions.

We should probably add a test

It's not worth it. We will not be able to make such tests stable and defensible. Please use compiled artifact to check locally.

Even with this, the hashset will still be accessed from multiple threads concurrently in the cases given in #15513, won't it?

A root of the issue was that second thread read the HashSet while first thread still initializes the HashSet.
The HashSet is used only in one place for reading so no need to concern more about race conditions.

We should probably add a test

It's not worth it. We will not be able to make such tests stable and defensible. Please use compiled artifact to check locally.

If the only writes are the ones when the object is generated :
s_contentHeaderSet.Add(HttpKnownHeaderNames.Allow);
s_contentHeaderSet.Add(HttpKnownHeaderNames.LastModified);
...

I think the write race condition is eliminated with this change.

I am a C# dev, but I have zero knowledge on the Powershell source code. Hope I could help you somehow.

I am a C# dev, but I have zero knowledge on the Powershell source code. Help I could help you somehow.

@dperez83 PowerShell is great project to improve skills. It's too big to learn it well in a short time but you can pick an area you like best and work there with some workgroup https://devblogs.microsoft.com/powershell/powershell-working-groups/
After monitoring issues and PRs for about a month you will be able to make good contributions.

PowerShell Team

PowerShell Working Groups | PowerShell Team

Since we open sourced PowerShell in 2016, PowerShell has been an immensely popular project on GitHub. Every year, 700-1000 PRs and 1300-1500 issues are submitted to the PowerShell repo, with roughly half of the PRs and 90% of the issues filed from the community.

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

@daxian-dbw Could you please review?

@SteveL-MSFT Could you please approve? It is impossible to merge without green flag :-)

This pull request has been automatically marked as Review Needed because it has been there has not been any activity for 7 days.
Maintainer, please provide feedback and/or mark it as Waiting on Author

I see that there's a pending review from @daxian-dbw
Is there anything else you need from me?

Thank you

@TravisEz13 Please review/approve.

🎉v7.2.0-preview.9 has been released which incorporates this pull request.:tada:

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🎉v7.2.0-preview.10 has been released which incorporates this pull request.:tada:

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