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

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Message-ID: <20170324204615.GB5680@worktop>
Date:   Fri, 24 Mar 2017 21:46:15 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.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 Fri, Mar 24, 2017 at 12:08:32PM -0700, Linus Torvalds wrote:
> On Fri, Mar 24, 2017 at 10:23 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > I tried a few variants, but nothing really made it better.
> 
> So I really hate how your thing has two return values, and fakes the
> second one using the pointer value. 

Inspired by C11 I'm afraid..

> So how about we change the interface entirely, with the goal being
> both type safety and good code generation?

I certainly like it better, but so far I'm having trouble reproducing
your results. What compiler version are you on?