* Thomas Gleixner <t...@linutronix.de> wrote:
> On Thu, 4 Feb 2016, Davidlohr Bueso wrote:
>
> > On Thu, 04 Feb 2016, Thomas Gleixner wrote:
> >
> > > On Wed, 3 Feb 2016, Davidlohr Bueso wrote:
> > > > + * We are not calling into get_futex_key_refs() in
> > > > file-backed
> > > > + * cases, therefore a successful atomic_inc return
> > > > below will
> > > > + * guarantee that get_futex_key() will continue to
> > > > imply MB
> > > > (B).
> > >
> > > Can you please make that "MB (B)" part a bit more outstanding. I really
> > > had
> > > to
> > > search for it.
> >
> > Hmm as you know this is mostly explained at the begining of the file, and we
> > sprinkle MB (B) around the code based on that description. So I'm a bit
> > confused
> > as to why you don't like like that comment.
>
> The other "MB (B)" places are more outstanding. It did not spring in my eye
> immideately. So it's a pure cosmetic issue.
So I too didn't understand that sentence at first, because the capitalization
really throws off quick parsing of that comment, as 'MB' ususally denotes
megabytes.
So please change it to "mb(); (A)" or so - and I think all of these comments
should be changed to use a standard API name for the barrier they imply, as the
head of futex.c does:
* waiters++; (a)
* mb(); (A) <-- paired with -.
* |
* lock(hash_bucket(futex)); |
* |
* uval = *futex; |
* | *futex = newval;
* | sys_futex(WAKE, futex);
* | futex_wake(futex);
* |
* `-------> mb(); (B)
Btw., pedantic: shouldn't that be smp_mb()? Futexes don't operate on IO spaces,
so
on UP they only need compiler barriers.
Thanks,
Ingo
