Re: RFC: localcount_hadref() or localcount_trydarin()

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

> Date: Mon, 12 Jun 2017 10:53:52 +0900
> From: Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>
> 
> I want to avoid detaching the encryption device while it is used by IPsec.
> That is, once someone creates Security Assocatation(SA) to call
> crypto_newsession(), the encryption device related the SA must not be
> detached until the SA is flushed(done crypto_freesession()) and the SA
> is not used(done crypto_dispatch() and cryptointr()).

Why don't you just use a global reference count first?  Is the latency
and scalability of crypto_newsession and crypto_freesession critical?

I am not familiar with opencrypto -- maybe the answer is yes.  But in
crypto_newsession, crypto_freesession, and cryptointr, you're still
acquiring a global lock.  That defeats the purpose of using
localcount, which is to make the latency and scalability of
acquire/release no more than a CPU-local integer increment.