TypeDescriptor.Refresh is not thread-safe

[stephentoub]

In general, static methods are supposed to be thread-safe, and there's no warning in the docs about it not being so.

But TypeDescriptor.Refresh may end up calling into ReflectTypeDescriptionProvider.GetPopulatedTypes. It does so while holding a lock GetPopulatedTypes enumerates the _typeData Hashtable. If a concurrent call to GetTypeData (which takes a different lock) mutates that hashtable, it invalidates the enumerator being used by GetPopulatedTypes, causing GetPopulatedTypes to throw an exception.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[ghost]

Tagging subscribers to this area: @safern
See info in area-owners.md if you want to be subscribed.

Issue Details

---

In general, static methods are supposed to be thread-safe, and there's no warning in the docs about it not being so.

But TypeDescriptor.Refresh may end up calling into ReflectTypeDescriptionProvider.GetPopulatedTypes. It does so while holding a lock But GetPopulatedTypes takes a different lock, and enumerates the _typeData Hashtable. If a concurrent call to GetTypeData adds to that Hashtable, it invalidates the enumerator being used by GetPopulatedTypes, causing GetPopulatedTypes to throw an exception.

Author:	stephentoub
Assignees:	-
Labels:	area-System.ComponentModel, untriaged
Milestone:	-

[FilipToth]

I don't understand why this method is static in the first place. Does it update the cache for all instances of the TypeDescriptor class?