On Mon, 25 Sep 2017, Peter Zijlstra wrote:
> On Thu, Aug 31, 2017 at 12:23:36PM -0000, Anna-Maria Gleixner wrote:
> > The hrtimer_cpu_base struct has the CONFIG_HIGH_RES_TIMERS conditional
> > struct member hres_active. All related functions to this member are
> > conditional as well.
> >
> > There is no functional change, when the hres_active member is unconditional
> > with all related functions and is set to zero during initialization. This
> > makes the code easier to read.
>
> But you make what was a compile time dead-code-elimination into a
> runtime load-and-branch.
>
> Unless the compiler is overly clever and is able to deduce from the lack
> of assignments that it must always be 0, is it?
Probably not. So the simple way to solve this is to make the new common
is_highres_active()
{
return IS_ENABLED(CONFIG_HIGH_RES) ? base->hres_active : 0;
}
Thanks,
tglx
