Can SnapshottingCollection.GetSnapshot() call CreateSnapshot() multiple times?

[omajid]

This code checks that snapshot == null before taking a lock, but never checks it again:

sdk/src/Cli/dotnet/Telemetry/PersistenceChannel/SnapshottingCollection.cs

Lines 79 to 92 in 88ec742

	protected TCollection GetSnapshot()
	{
	TCollection localSnapshot = snapshot;
	if (localSnapshot == null)
	{
	lock (Collection)
	{
	snapshot = CreateSnapshot(Collection);
	localSnapshot = snapshot;
	}
	}
	return localSnapshot;
	}

I think this sequence of events can result in multiple calls to CreateSnapshot():

1. Thread 1 calls GetSnapshot() and see localSnapshot = snapshot && localSnapshot == null
2. Thread 2 calls GetSnapshot() and see localSnapshot = snapshot && localSnapshot == null
3. Thread 1 enters the lock block, and runs CreateSnapshot, and updates snapshot
4. Thread 2 enters the lock block, runs CreateSnapshot again, and updates snapshot again.