linux-kernel - Re: [PATCH v3] Avoid memory barrier in read

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Message-ID: <797cf697-83b2-7f45-4865-2ee394887dc8@gentwo.org>
Date: Fri, 25 Oct 2024 12:30:32 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Peter Zijlstra <peterz@...radead.org>
cc: Linus Torvalds <torvalds@...ux-foundation.org>, 
    Will Deacon <will@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
    Catalin Marinas <catalin.marinas@....com>, Ingo Molnar <mingo@...hat.com>, 
    Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
    linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
    linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load
 acquire

On Fri, 25 Oct 2024, Peter Zijlstra wrote:

> > atomic_inc_release(&seqcount)
>
> It would not be, making the increment itself atomic would make the whole
> thing far more expensive.

True. I was too much taken by a cool hw feature on ARM.