Re: sem_lock() vs qspinlocks

[Linus Torvalds]

On Mon, May 23, 2016 at 5:25 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Paul has smp_mb__after_unlock_lock() for the RCpc 'upgrade'. How about
> something like:
>
>         smp_mb__after_lock()

I'd much rather make the naming be higher level. It's not necessarily
going to be a "mb", and while the problem is about smp, the primitives
it is synchronizing aren't actually smp-specific (ie you're
synchronizing a lock that is relevant on UP too).

So I'd just call it something like

        spin_lock_sync_after_lock();

because different locks might have different levels of serialization
(ie maybe a spinlock needs one thing, and a mutex needs another - if
we start worrying about ordering between spin_lock and
mutex_is_locked(), for example, or between mutex_lock() and
spin_is_locked()).

Hmm?

                     Linus