Re: [RFC 0/2] srcu: Remove pre-flip memory barrier

Frederic Weisbecker
2022-12-20T22:58:27Z

On Tue, Dec 20, 2022 at 02:01:30PM -0500, Mathieu Desnoyers wrote:
> On 2022-12-20 13:29, Joel Fernandes wrote:
> >
>
> > I do want to finish my memory barrier studies of SRCU over the holidays since I have been deep in the hole with that already. Back to the post flip memory barrier here since I think now even that might not be needed…
>
> I strongly suspect the memory barrier after flip is useless for the same
> reasons I mentioned explaining why the barrier before the flip is useless.
>
> However, we need to double-check that we have memory barriers at the
> beginning and end of synchronize_srcu, and between load of "unlock" counters
> and load of "lock" counters.
>
> Where is the barrier at the beginning of synchronize_srcu ?

rcu_seq_snap() ?

>
> Thanks,
>
> Mathieu
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
>