Re: [PATCH 00/22] add support for Clang LTO

Paul E. McKenney
2020-07-06T18:39:53Z

On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote:
>
> > And perhaps more constructively, we do need to prioritize address and data
> > dependencies over control dependencies. For one thing, there are a lot
> > more address/data dependencies in existing code than there are control
> > dependencies, and (sadly, perhaps more importantly) there are a lot more
> > people who are convinced that address/data dependencies are important.
>
> If they do not consider their Linux OS running correctly :-)

Many of them really do not care at all. In fact, some would consider
Linux failing to run as an added bonus.

> > For another (admittedly more theoretical) thing, the OOTA scenarios
> > stemming from control dependencies are a lot less annoying than those
> > from address/data dependencies.
> >
> > And address/data dependencies are as far as I know vulnerable to things
> > like conditional-move instructions that can cause problems for control
> > dependencies.
> >
> > Nevertheless, yes, control dependencies also need attention.
>
> Today I added one more \o/

Just make sure you continually check to make sure that compilers
don't break it, along with the others you have added. ;-)

Thanx, Paul