irqdesc: Why the "__ref" is needed in __irq_alloc_descs() ?

[Dou Liyang]

Hi Maintainers,

I have a question about "__ref" in Linux kernel.

When I looked into the __irq_alloc_descs(), I found it tagged a
"__ref" mark, but I didn't find that it referenced code or data
from init section.

So, I confuse why the "__ref"  is needed in __irq_alloc_descs()?
any other reasons?

And after I tested, seems "__ref" just puts the code into a different
section that is not checked by modpost. It does not affect the
performance whether it is tagged or not. Is it right?

Thanks,
	dou.