Threading issues with DirectoryUtility.CreateSharedDirectory cause failures in restore/pack on Linux/Mac

[nkolev92]

Likely root cause of #7341.

This is the issue tracking the fix. The other issue has lots of engagement and I want to avoid closing it before getting a confirmation that the issues have been fixed.

NuGet/NuGet.Client#2795

During the investigation of #7908, I found that this utility has threading issues. I have a test app that reliably repros the behavior: https://github.com/nkolev92/NuGet.Tools/tree/master/DirectoryUtilityRepro/TestApp

The Directory.CreateDirectory & Directory.Move methods do not guarantee thread safety. They merely guarantee filesystem consistency.

Through my tests I narrowed down the issue to Directory.Move not throwing every time when the dest path exists in the case where multiple threads are trying to create the same directory. Directory.Move never claims thread safety, but rather only filesystem consistency. Effectively on Linux we’d have multiple moves succeed, because the underlying “rename” syscall allows for the destdir to be overridden.

[nkolev92]

Fixed in NuGet/NuGet.Client#2795