linux-kernel - Re: [PATCH 27/34] sched_ext: Implement SCX_KICK

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wiT-nr-kRON8vToQSbMhijztp8LV=Y0PgjLJhgDPckxPA@mail.gmail.com>
Date:   Thu, 13 Jul 2023 11:32:37 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andrea Righi <andrea.righi@...onical.com>
Cc:     Tejun Heo <tj@...nel.org>, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...nel.org, joshdon@...gle.com, brho@...gle.com,
        pjt@...gle.com, derkling@...gle.com, haoluo@...gle.com,
        dvernet@...a.com, dschatzberg@...a.com, dskarlat@...cmu.edu,
        riel@...riel.com, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH 27/34] sched_ext: Implement SCX_KICK_WAIT

On Thu, 13 Jul 2023 at 06:46, Andrea Righi <andrea.righi@...onical.com> wrote:
>
> I'm not sure if we already have an equivalent of
> smp_store_release_u64/smp_load_acquire_u64(). Otherwise, it may be worth
> to add them to a more generic place.

Yeah, a 64-bit atomic load/store is not necessarily even possible on
32-bit architectures.

And when it *is* possible, it might be very very expensive indeed (eg
on 32-bit x86, the way to do a 64-bit load would be with "cmpxchg8b",
which is ridiculously slow)

              Linus