linux-kernel - Re: [PATCH 4/6] lib/refcount: Move bulk of REFCOUNT

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Message-ID: <201908021915.95BD6B26FC@keescook>
Date:   Fri, 2 Aug 2019 19:23:07 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Hanjun Guo <guohanjun@...wei.com>,
        Jan Glauber <jglauber@...vell.com>
Subject: Re: [PATCH 4/6] lib/refcount: Move bulk of REFCOUNT_FULL
 implementation into header

On Fri, Aug 02, 2019 at 08:52:22PM +0200, Peter Zijlstra wrote:
> On Fri, Aug 02, 2019 at 11:09:58AM +0100, Will Deacon wrote:
> > In an effort to improve performance of the REFCOUNT_FULL implementation,
> > move the bulk of its functions into linux/refcount.h. This allows them
> > to be inlined in the same way as if they had been provided via
> > CONFIG_ARCH_HAS_REFCOUNT.
> 
> Hehe, they started out this way, then Linus said to stuff them in a C
> file :-)

I asked this at the time and didn't quite get a straight answer; Linus's
request was private:

https://lore.kernel.org/lkml/20170213180020.GK6500@twins.programming.kicks-ass.net/

It seemed sensible to me (then and now) to have them be inline if there
were so many performance concerns about it, etc. Was it just the image
size bloat due to the WARNs? So... since we're back to this topic. Why
should they not be inline?

-- 
Kees Cook