[release/6.0] Fix DNS cancellation deadlock

[github-actions]

Fixes #63552
Backport of #63904 to release/6.0

/cc @rzikm @antonfirsov

Customer Impact

Customer reported hang calling Dns.GetHostAddressesAsync. This is because when cancellation kicks in during DNS call, it can lead to deadlock.

Testing

Tested on locally built runtime bits from this branch and running the repro app from the original issue.

Risk

Low -- Removal of a lock which was not necessary in the first place, see original PR. Change has been in main for over 2 months.

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Issue Details

---

Backport of #63904 to release/6.0

/cc @rzikm @antonfirsov

Customer Impact

Testing

Risk

IMPORTANT: If this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.

Author:	github-actions[bot]
Assignees:	-
Labels:	area-System.Net
Milestone:	-

[rzikm]

Windows CI failures are Helix queue windows.10.amd64.server19h1.es.open is set for estimated removal date of 2022-03-31.

[ManickaP]

Windows CI failures are Helix queue windows.10.amd64.server19h1.es.open is set for estimated removal date of 2022-03-31.

@CarnaViire isn't this similar to your recent struggles with 6.0 branch?

[CarnaViire]

@CarnaViire isn't this similar to your recent struggles with 6.0 branch?

Yes. The tracking issue is #67048

[danmoseley]

This doesn't need packaging work, right?

[antonfirsov]

This doesn't need packaging work, right?

Fortunately not, it's BCL System.Net.NameResolution.

[danmoseley]

This got approved for 6.0 conditional on (if possible) the original customer validating (at least on 7.0)

@MartyIX did you get a chance to try a 7.0 build to verify that it seems to fix it for you.

[MartyIX]

@MartyIX did you get a chance to try a 7.0 build to verify that it seems to fix it for you.

Looking at https://github.com/dotnet/runtime/releases and 7.0 preview 2 was released 22 days ago and the original bugfix being merged 16 days ago, I don't think there is a public release for me to test.

Or is there a way to download something like "the latest dotnet/runtime binary/build for Windows" without me having to compile everything?

[rzikm]

You can download latest builds from https://github.com/dotnet/installer#table

[MartyIX]

@danmoseley So I have run a few times the repro program on .NET 6 and .NET 7 (thanks @rzikm) and it appears to be fixed in .NET 7 as it finishes as expected. I don't observe any deadlock or "unnecessary" delay.

Thank you

---

global.json for .NET 7 testing:

{
  "sdk": {
    "version": "7.0.0-preview.3.22175.4",
    "rollForward": "latestFeature"
  }
}

[danmoseley]

Thanks for confirming @MartyIX . This will be merged next week for the May servicing release.