Re: [PATCH 3/3] fork, vhost: Use CLONE_THREAD to fix freezer/ps regression

[Linus Torvalds]

On Fri, Jun 2, 2023 at 1:59 PM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> As I said from the very beginning, this code is fine on x86 because
> atomic ops are fully serialised on x86.

Yes. Other architectures require __smp_mb__{before,after}_atomic for
the bit setting ops to actually be memory barriers.

We *should* probably have acquire/release versions of the bit test/set
helpers, but we don't, so they end up being full memory barriers with
those things. Which isn't optimal, but I doubt it matters on most
architectures.

So maybe we'll some day have a "test_bit_acquire()" and a
"set_bit_release()" etc.

            Linus