Re: [PATCH] rwsem: fix missed wakeup due to reordering of load

[Davidlohr Bueso]

On Wed, 20 Sep 2017, Andrea Parri wrote:

> > Instead, how about just removing the release from atomic_long_sub_return_release()
> > such that the osq load is not hoisted over the atomic compound (along with Peter's
> > comment):
>
> This solution will actually enforce a stronger (full) ordering w.r.t. the
> solution described by Prateek and Peter. Also, it will "trade" two lwsync
> for two sync (powerpc), one dmb.ld for one dmb (arm64).
>
> What are the reasons you would prefer this?

It was mainly to maintain consistency about dealing with sem->count, but sure
I won't argue with the above.