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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 13 Jul 2023 11:32:37 -0700
Message-ID: <CAHk-=wiT-nr-kRON8vToQSbMhijztp8LV=Y0PgjLJhgDPckxPA@mail.gmail.com>
Subject: Re: [PATCH 27/34] sched_ext: Implement SCX_KICK_WAIT
To:     Andrea Righi <andrea.righi@canonical.com>
Cc:     Tejun Heo <tj@kernel.org>, mingo@redhat.com, peterz@infradead.org,
        juri.lelli@redhat.com, vincent.guittot@linaro.org,
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On Thu, 13 Jul 2023 at 06:46, Andrea Righi <andrea.righi@canonical.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