Date: Sat, 25 Mar 2017 19:20:23 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Josh Poimboeuf <jpoimboe@redhat.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: locking/atomic: Introduce atomic_try_cmpxchg()
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On Sat, Mar 25, 2017 at 11:00:44AM -0700, Linus Torvalds wrote:
> On Sat, Mar 25, 2017 at 12:51 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Fri, Mar 24, 2017 at 10:23:29PM +0100, Peter Zijlstra wrote:
> >
> >> I'll try and redo the patches that landed in tip and see what it does
> >> for total vmlinux size somewhere tomorrow.
> >
> >    text    data     bss     dec     hex filename
> > 10726413        4540256  843776 16110445         f5d36d defconfig-build/vmlinux.pre
> > 10730509        4540256  843776 16114541         f5e36d defconfig-build/vmlinux.post
    10730445        4540256  843776 16114477         f5e32d defconfig-build/vmlinux

> >
> > :-(
> 
> Hmm. But you are comparing against the *broken* version that did the
> unconditional store of the result.

Well, only broken if not used on stack local variables, but yes.

> You should at least compare against the fixed version with the
> conditional store. That's the one that was hard to get good code
> generation from, wasn't it?

Added above, a few bytes smaller than the shiny new one actually.