Re: [RFC][PATCH 2/3] locking: Annotate spin_unlock_wait() users

[Peter Zijlstra]

On Tue, May 24, 2016 at 09:17:13AM -0700, Linus Torvalds wrote:

> This needs to be either hidden inside the basic spinlock functions,
> _or_ it needs to be a clear and unambiguous interface. Anything that
> starts talking about control dependencies is not it.
> 
> Note that this really is about naming and use, not about
> implementation. So something like "spin_sync_after_unlock_wait()" is
> acceptable, even if the actual _implementation_ were to be exactly the
> same as the "after_ctrl_dep()" crap.

OK; so I would prefer to keep the smp_acquire__after_ctrl_dep() crap for
common use in smp_cond_acquire() and such, but I'd be more than happy to
just stuff it unconditionally into spin_unlock_wait().

Most users really need it, and its restores intuitive semantics to the
primitive.

I'm assuming the explicit use then left in ipc/sem.c (as paired with the
spin_is_locked) is fine with you; that's certainly not driver code.

Todays series was really more about auditing all the spin_unlock_wait()
usage sites.