[PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop

[Peter Zijlstra]

On Tue, Dec 06, 2016 at 11:03:28AM -0500, Waiman Long wrote:
> 
> The mutex_spin_on_owner() function was originally marked noinline
> because it could be a major consumer of CPU cycles in a contended lock.
> Having it shown separately in the perf output will help the users have a
> better understanding of what is consuming all the CPU cycles. So I would
> still like to keep it this way.

ah!, I tried to dig through history but couldn't find a reason for it.

> 
> If you have concern about additional latency for non-ww_mutex calls, one
> alternative can be:

That's pretty horrific :/