What is the point of this function?
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.
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
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
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
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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
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-- "Do or do not. There is no try" Yoda Master
participants (3)
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Andrea Benelli -
Daniel. -
Nathan Williams