[resolved] Why don't .NET use CAS in ConcurrentDictionary Get?

[Cyl18]

[resolved]

runtime/src/libraries/System.Collections.Concurrent/src/System/Collections/Concurrent/ConcurrentDictionary.cs

Line 486 in cb5431d

for (Node? n = Volatile.Read(ref tables.GetBucket(hashcode)); n != null; n = n._next)

Volatile.Read inserts a memory barrier which might be performance consuming.
Why not to use CAS? And what's the difference between CAS and memory barrier?

[LeaFrock]

So... why is this question resolved?

[huoyaoyuan]

The question is misunderstanding about "memory barrier".

The barrier means correctness of execution order. It has no relationship with "security barrier".

[PathogenDavid]

@huoyaoyuan Pretty sure CAS in this context is compare-and-swap (IE: Interlocked.CompareExchange), not code access security. (The latter is what my mind jumped to as well though.)