Re: [PATCH v2] X86: Hook apic vector allocation domain only when interrupt routing are set to ignore

[Ingo Molnar <mingo@kernel.org>]

* Oren Twaig <oren@scalemp.com> wrote:

> Hi Andi,
> 
> On 04/25/2014 05:22 PM, Andi Kleen wrote:
> >> +static int irc = 1;
> >
> > Using a static for such state is very unusual. You need to 
> > describe what protects it against races and why that is needed 
> > over a cleaner solution.
> 
> The only reason I've used a static variable is because I wanted to 
> avoid inserting another code/functions which are depended on 
> CONFIG_PCI.  The code is used once during initialization and hence 
> cannot be racy.
> 
> But, if static variables are unusual (new at linux kernel), [...]

They aren't unusual at all - Andi Kleen is a known to troll x86 
discussions time and again with random input, just ignore it when you 
get bad advice.

> [...] I will change the flow to read the HW state again (using the 
> PCI functions).  Please let me know if that is desirable.

No, being slower is not desirable.

Maybe name the flag in a clearer fashion (the term 'irc' is used for 
something entirely different, most of the time), i.e. make sure it's 
very obvious that it's a set-once init flag.

Thanks,

	Ingo