Messages in this thread | | | Date | Thu, 4 Feb 2016 18:50:07 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH v5] futex: Remove requirement for lock_page in get_futex_key |
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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.
> > > + */ > > > + if (WARN_ON_ONCE(!atomic_inc_not_zero(&inode->i_count))) { > > > + rcu_read_unlock(); > > > + put_page(page); > > > + > > > + goto again; > > > + } > > > > Don't we need > > > > smp_mb__after_atomic(); > > > > here to make it a full barrier on all architectures? > > I had this initially but, as Peter mentioned, we get that barrier with the > successful atomic_inc_not_zero call anyway. Or is it something else you had > in mind?
Oh. I missed that comment from Peter. And yes, I missed that atomic_inc_not_zero() already has the barrier in the success case. :(
Thanks,
tglx
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