linux-kernel - Re: [PATCH 0/7] atomics: generate atomic headers

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Message-ID: <20180605142356.tje7h7sr67quxdju@lakrids.cambridge.arm.com>
Date:   Tue, 5 Jun 2018 15:23:57 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, boqun.feng@...il.com,
        will.deacon@....com, arnd@...db.de, aryabinin@...tuozzo.com,
        dvyukov@...gle.com, glider@...gle.com, gregkh@...uxfoundation.org,
        jslaby@...e.com, parri.andrea@...il.com
Subject: Re: [PATCH 0/7] atomics: generate atomic headers

On Tue, Jun 05, 2018 at 04:14:16PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 05, 2018 at 02:58:23PM +0100, Mark Rutland wrote:
> 
> > Sure, it all works, it's just less than optimal as above, and also means
> > that we have to duplicate the ifdeffery for optional atomics -- once in
> > the instrumented atomics, then in the "real" atomics.
> > 
> > Whereas if we filled in the raw atomics atop of the arch atomics,
> > everything above that can assume the whole API is present, no ifdeffery
> > required.
> 
> Aah, I see your point now. I don't think performance is a particular
> concern when you enable K*SAN, but getting rid of a fair bunch of
> ifdeffery is always nice.

I agree that performance isn't a concern there when debugging, but I
would like to keep the overhead down when fuzzing.

Regardless, we'd have to move arches over to arch_atomic_* first, and
once that's done the raw_atomic_* stuff is fairly easy to implement by
reworking the scripts.

Thanks,
Mark.