What is the point of this function?

What is the point of this function?

[Andrea Benelli]

Hello, i was looking at the *linux/sched.h* (kernel version 4.6.2) source
code and i found this function at line *1174*:

static inline bool cpus_share_cache(int this_cpu, int that_cpu)
{
        return true;
}

I'm not able to understand the utility of a function that just return a
true value.
i've noticed that there are a lot of functions like this (function that
just return a constant).

so...why?
thanks.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20160621/5be09bcd/attachment.html 

What is the point of this function?

[Nathan Williams]

On Tue, 2016-06-21 at 00:48 +0200, Andrea Benelli wrote:
> Hello, i was looking at the linux/sched.h (kernel version 4.6.2)
> source code and i found this function at line 1174: 
> 
> static inline bool cpus_share_cache(int this_cpu, int that_cpu)
> {
>         return true;
> }
> 
> I'm not able to understand the utility of a function that just return
> a true value. 
> i've noticed that there are a lot of functions like this (function
> that just return a constant). 

Hi Andrea,

That's the case for when CONFIG_SMP isn't defined. What happens when
CONFIG_SMP is defined?

I suggest having a look through the code with a Linux cross reference:

http://lxr.free-electrons.com/ident?v=4.6;i=cpus_share_cache

Regards,
Nathan

What is the point of this function?

[Andrea Benelli]

So, it's just an override?
Why return true and not false?
Il 21 giu 2016 4:32 AM, "Nathan Williams" <ngwilliams@gmail.com> ha scritto:

> On Tue, 2016-06-21 at 00:48 +0200, Andrea Benelli wrote:
> > Hello, i was looking at the linux/sched.h (kernel version 4.6.2)
> > source code and i found this function at line 1174:
> >
> > static inline bool cpus_share_cache(int this_cpu, int that_cpu)
> > {
> >         return true;
> > }
> >
> > I'm not able to understand the utility of a function that just return
> > a true value.
> > i've noticed that there are a lot of functions like this (function
> > that just return a constant).
>
> Hi Andrea,
>
> That's the case for when CONFIG_SMP isn't defined. What happens when
> CONFIG_SMP is defined?
>
> I suggest having a look through the code with a Linux cross reference:
>
> http://lxr.free-electrons.com/ident?v=4.6;i=cpus_share_cache
>
> Regards,
> Nathan
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20160621/36e5606f/attachment-0001.html 

What is the point of this function?

[Daniel.]

The function body you see will be use only when CONFIG_SMP is not
present. Take a look at
https://www.kernel.org/doc/Documentation/CodingStyle
Chapter 20: Conditional Compilation

Regards,

2016-06-21 8:56 GMT-03:00 Andrea Benelli <andreabenelli77@gmail.com>:
> So, it's just an override?
> Why return true and not false?
>
> Il 21 giu 2016 4:32 AM, "Nathan Williams" <ngwilliams@gmail.com> ha scritto:
>>
>> On Tue, 2016-06-21 at 00:48 +0200, Andrea Benelli wrote:
>> > Hello, i was looking at the linux/sched.h (kernel version 4.6.2)
>> > source code and i found this function at line 1174:
>> >
>> > static inline bool cpus_share_cache(int this_cpu, int that_cpu)
>> > {
>> >         return true;
>> > }
>> >
>> > I'm not able to understand the utility of a function that just return
>> > a true value.
>> > i've noticed that there are a lot of functions like this (function
>> > that just return a constant).
>>
>> Hi Andrea,
>>
>> That's the case for when CONFIG_SMP isn't defined. What happens when
>> CONFIG_SMP is defined?
>>
>> I suggest having a look through the code with a Linux cross reference:
>>
>> http://lxr.free-electrons.com/ident?v=4.6;i=cpus_share_cache
>>
>> Regards,
>> Nathan
>>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>



-- 
"Do or do not. There is no try"
  Yoda Master

What is the point of this function?

[Andrea Benelli]

Ok, thank you!
Il 22 giu 2016 3:08 PM, "Daniel." <danielhilst@gmail.com> ha scritto:

> The function body you see will be use only when CONFIG_SMP is not
> present. Take a look at
> https://www.kernel.org/doc/Documentation/CodingStyle
> Chapter 20: Conditional Compilation
>
> Regards,
>
> 2016-06-21 8:56 GMT-03:00 Andrea Benelli <andreabenelli77@gmail.com>:
> > So, it's just an override?
> > Why return true and not false?
> >
> > Il 21 giu 2016 4:32 AM, "Nathan Williams" <ngwilliams@gmail.com> ha
> scritto:
> >>
> >> On Tue, 2016-06-21 at 00:48 +0200, Andrea Benelli wrote:
> >> > Hello, i was looking at the linux/sched.h (kernel version 4.6.2)
> >> > source code and i found this function at line 1174:
> >> >
> >> > static inline bool cpus_share_cache(int this_cpu, int that_cpu)
> >> > {
> >> >         return true;
> >> > }
> >> >
> >> > I'm not able to understand the utility of a function that just return
> >> > a true value.
> >> > i've noticed that there are a lot of functions like this (function
> >> > that just return a constant).
> >>
> >> Hi Andrea,
> >>
> >> That's the case for when CONFIG_SMP isn't defined. What happens when
> >> CONFIG_SMP is defined?
> >>
> >> I suggest having a look through the code with a Linux cross reference:
> >>
> >> http://lxr.free-electrons.com/ident?v=4.6;i=cpus_share_cache
> >>
> >> Regards,
> >> Nathan
> >>
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
>
>
>
> --
> "Do or do not. There is no try"
>   Yoda Master
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20160623/da155a5e/attachment.html