Re: [PATCH] ptrace: restore smp_rmb() in __ptrace_may_access()

[Oleg Nesterov <oleg@redhat.com>]

On 05/29, Jann Horn wrote:
>
> > (I am wondering if smp_acquire__after_ctrl_dep() could be used instead, just to
> >  make this code look more confusing)
>
> Uuh, I had no idea that that barrier type exists. The helper isn't
> even explicitly mentioned in Documentation/memory-barriers.rst. I
> don't really want to use dark magic in the middle of ptrace access
> logic...

Yes. and if it was not clear I didn't try to seriously suggest to use this
barrier. I was just curious if it can be used or not in this particular case.

> Anyway, looking at it, I think smp_acquire__after_ctrl_dep() doesn't
> make sense here;

Well I still _think_ it should work, it provides the LOAD-LOAD ordering
and this is what we need.

But I can be easily wrong, and again, I wasn't serious.

Oleg.