linux-kernel - Re: locking/atomic: Introduce atomic_try

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Message-ID: <CA+55aFwy+HsHZFvv0FtvnLGDEEGMxc5dz3hXQWjJ4nOdfFL1-Q@mail.gmail.com>
Date:   Sat, 25 Mar 2017 11:28:35 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: locking/atomic: Introduce atomic_try_cmpxchg()

On Sat, Mar 25, 2017 at 11:20 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>
> Added above, a few bytes smaller than the shiny new one actually.

Hmm. Sad. The label approach looked like it would match the semantics
of cmpxchg perfectly, but it's not as optimal as it superficially
would have seemed.

And I assume that register allocation etc is different enough that
there's no sane way to diff the asm to see what changed.

           Linus