linux-kernel - Re: [RESEND PATCH v7 2/7] arm64: barrier: Support smp_cond_load_relaxed

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Message-ID: <82febb6d-ba14-6a23-1955-9d505372dc23@gentwo.org>
Date: Tue, 28 Oct 2025 09:21:50 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Arnd Bergmann <arnd@...db.de>
cc: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org, 
    Linux-Arch <linux-arch@...r.kernel.org>, 
    linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org, 
    bpf@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>, 
    Will Deacon <will@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Mark Rutland <mark.rutland@....com>, Haris Okanovic <harisokn@...zon.com>, 
    Alexei Starovoitov <ast@...nel.org>, 
    "Rafael J . Wysocki" <rafael@...nel.org>, 
    Daniel Lezcano <daniel.lezcano@...aro.org>, 
    Kumar Kartikeya Dwivedi <memxor@...il.com>, zhenglifeng1@...wei.com, 
    xueshuai@...ux.alibaba.com, Joao Martins <joao.m.martins@...cle.com>, 
    Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
    Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [RESEND PATCH v7 2/7] arm64: barrier: Support
 smp_cond_load_relaxed_timeout()

On Tue, 28 Oct 2025, Arnd Bergmann wrote:

> After I looked at the entire series again, this one feels like
> a missed opportunity. Especially on low-power systems but possibly
> on any ARMv9.2+ implementation including Cortex-A320, it would
> be nice to be able to both turn off the event stream and also
> make this function take fewer wakeups:

That is certainly something that should be done at some point but for now
this patchset does the best possible with the available systems.

Switching of the event stream is another set of complexities that should
be handled separately later.

Lets just get this one finally in. We have been working on this issue
now for more than 2 years.