Re: [PATCH v2 0/9] Remove spin_unlock_wait()

From: Ingo Molnar
Date: Fri Jul 07 2017 - 04:06:33 EST

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> > It might even be that this is the defined semantics of spin_unlock_wait().
> As is, spin_unlock_wait() is somewhat ill defined. IIRC it grew from an
> optimization by Oleg and subsequently got used elsewhere. And it being the
> subtle bugger it is, there were bugs.

I believe the historical, original spin_unlock_wait() came from early SMP
optimizations of the networking code - and then spread elsewhere, step by step.
All but one of the networking uses went away since then - so I don't think there's
any original usecase left.