On Wed, 2014-11-05 at 10:00 -0500, Steven Rostedt wrote: 

On Wed, 5 Nov 2014 15:43:24 +0100
Juerg Haefliger [off-list ref] wrote:

quoted

Thanks for the explanation. So is this considered a temporary failure
until multiple readers are allowed or does cpufreq need fixing or
something else? Just trying to figure out what to do next.

Good question. Unfortunately I don't know the answer to that.

[RFC PATCH RT] rwsem: The return of multi-reader PI rwsems

The above springs to mind.

-Mike