Re: [GIT PULL] ring-buffer: Replace this_cpu_*() with __this_cpu_*()

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 19 May 2015 10:35:32 -0500 (CDT)
Christoph Lameter <cl@linux.com> wrote:

> On Thu, 19 Mar 2015, Steven Rostedt wrote:
> 
> > On Thu, 19 Mar 2015 15:16:25 -0700
> > Linus Torvalds <torvalds@linux-foundation.org> wrote:
> >
> > > So I don't think the ring-buffer change is necessarily _wrong_, but if
> > > this is a performance issue, why don't we just fix it up for the
> > > generic case rather than for just one user?
> >
> > I totally agree with your analysis, but it's up to Christoph to come up
> > with an answer to your questions.
> 
> Something beyond: Do not use this_cpu_* when preemption is already
> off but use __this_cpu_*?

I think the question was, why exactly does the generic this_cpu_read()
require disabling preemption? What breaks if it is not disabled?

-- Steve