Re: [PATCH] x86/resctrl: avoid compiler optimization in __resctrl_sched_in

[Jakub Jelinek]

On Tue, Mar 07, 2023 at 12:43:16PM -0600, Segher Boessenkool wrote:
> On Tue, Mar 07, 2023 at 12:35:45PM +0100, Peter Zijlstra wrote:
> > So per that summary, I'm going to nit-pick and state we very much want
> > CSE. CSE good. What we don't want it violating store-load ordering.
> 
> So you need to describe exactly what you *do* want.  There is no way to
> forbid most otherwise valid things.  But you can express pretty much all
> dependencies.
> 
> > Oh, geez, what a twisty tale that... So Linus knew back in '09 that "p"
> > was icky, but it sorta was the only thing and it 'worked' -- until now
> > :/
> 
> The "p" constraint is just like any other address_constraint, in most
> aspects.  Since this is very specific to "p", that limits what is going
> on to really just one thing.

Are we actually talking here about "p" constraint or about p/P (x86) modifiers
(asm ("%p0" : : "i" (42));)?

	Jakub