Re: [PATCH v9 11/17] mm: replace vm_lock and detached flag with a reference count

Mateusz Guzik
2025-01-11T20:31:45Z

On Sat, Jan 11, 2025 at 9:14 PM Suren Baghdasaryan <surenb@google.com> wrote:
>
> On Sat, Jan 11, 2025 at 3:24 AM Mateusz Guzik <mjguzik@gmail.com> wrote:
> > The previous modification of this spot to raw_read_seqcount loses the
> > acquire fence, making the above comment not line up with the code.
>
> Is it? From reading the seqcount code
> (https://elixir.bootlin.com/linux/v6.13-rc3/source/include/linux/seqlock.h#L211):
>
> raw_read_seqcount()
> seqprop_sequence()
> __seqprop(s, sequence)
> __seqprop_sequence()
> smp_load_acquire()
>
> smp_load_acquire() still provides the acquire fence. Am I missing something?
>

That's fine indeed.

In a different project there is an equivalent API which skips
barriers, too quick glance suggested this is what's going on here. My
bad, sorry for false alarm on this front. :)

--
Mateusz Guzik <mjguzik gmail.com>