Fix contention in LoggerFactory.CreateLogger #87904
Merged
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Some ASP.NET code paths end up calling this a lot, and it takes a lock on every call, even though the vast majority are satisifed by the cache and require no mutation. We can use a ConcurrentDictionary instead of a Dictionary, with double-checked locking. Nothing is ever removed from or overwritten in the dictionary, so there's no problem doing the hot-path read outside of the lock; we still do the mutation inside of the lock so that all of the mutation work is performed atomically and synchronized with the actions from AddProvider and RefreshFilter.
Fixes #83609