Re: [PATCH] locking/qspinlock: Use atomic_sub_return_release in queued_spin_unlock

[Davidlohr Bueso]

On Fri, 03 Jun 2016, Pan Xinhui wrote:

> The existing version uses a heavy barrier while only release semantics
> is required. So use atomic_sub_return_release instead.
>
> Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>

I just noticed this change in -tip and, while I know that saving a barrier
in core spinlock paths is perhaps a worthy exception, I cannot help but
wonder if this is the begging of the end for smp__{before,after}_atomic().