linux-kernel - Re: [PATCH] refcount: provide same memory ordering guarantees as in atomic

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Date:   Mon, 23 Oct 2017 15:12:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Elena Reshetova <elena.reshetova@...el.com>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        keescook@...omium.org, tglx@...utronix.de, mingo@...hat.com,
        ishkamiel@...il.com
Subject: Re: [PATCH] refcount: provide same memory ordering guarantees as in
 atomic_t

On Mon, Oct 23, 2017 at 02:09:44PM +0300, Elena Reshetova wrote:
> Currently arch. independent implementation of refcount_t in
> lib/refcount.c provides weak memory ordering guarantees
> compare to its analog atomic_t implementations.
> While it should not be a problem for most of the actual
> cases of refcounters, it is more understandable for everyone
> (and more error-prone for future users) to provide exactly
> same memory ordering guarantees as atomics.
> 
> If speed is of a concern, then either more efficient arch.
> dependent refcount_t implementation should be used or if there
> are enough users in the future we might need to provide both
> strict and relaxed refcount_t APIs.
> 
> Suggested-by: Kees Cook <keescook@...omium.org>

NAK