linux-kernel - Re: linux-next: manual merge of the akpm tree with the tip tree

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Date:   Fri, 24 Mar 2017 09:05:39 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
        linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: linux-next: manual merge of the akpm tree with the tip tree

On Fri, Mar 24, 2017 at 04:40:26PM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> Today's linux-next merge of the akpm tree got a conflict in:
> 
>   arch/x86/include/asm/atomic.h
> 
> between commit:
> 
>   e6790e4b5d5e ("locking/atomic/x86: Use atomic_try_cmpxchg()")
> 
> from the tip tree and patch:
> 
>   "x86/atomic: move __arch_atomic_add_unless out of line"
> 
> from the akpm tree.

Urgh, that patch shouldn't be in mm in any case. Also with the
try_cmpxchg() change, the text gain is reduced (about half).

Furthermore, micro-benchmarks show that turning cmpxchg loops like this
into a function makes them more expensive; see:

  https://lkml.kernel.org/r/20170322165144.dtidvvbxey7w5pbd@hirez.programming.kicks-ass.net