All semaphor all the time

[scbedd]

This cuts out all lock usage for await SemaphorSlim.WaitAsync() to synchronize resource access.

Originally, we had 3 possible locks

• object SessionSanitizerLock
• Session.Entries
• object Session.SanitizerLock

This moves to using a semaphore for these. Unfortunately this has the impact of forcing async in a lot of places that didn't use it before, so I've got some test pain to resolve as a result.

@mikeharder I'm very pleased with this one!

[mikeharder]

I agree this is better than synchronous locking. You generally want to use async as much as possible inside asp.net apps.

However, it is still susceptible to deadlocks and/or race conditions, if we don't have the locking semantics/ordering exactly correct. So if this doesn't fix all the issues, we might need to take a closer look at the algorithms we are using,.