perf events ring buffer memory barrier on powerpc

[Victor Kaplansky]

"David Laight" <David.Laight at aculab.com> wrote on 11/01/2013 06:25:29 PM:
> gcc will do unexpected memory accesses for bit fields that are
> adjacent to volatile data.
> In particular it may generate 64bit sized (and aligned) RMW cycles
> when accessing bit fields.
> And yes, this has caused real problems.

Thanks, I am aware about this bug/feature in gcc.
-- Victor