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* irqdesc: Why the "__ref" is needed in __irq_alloc_descs() ?
@ 2018-03-09  7:07 Dou Liyang
  2018-03-09 11:39 ` Thomas Gleixner
  0 siblings, 1 reply; 2+ messages in thread
From: Dou Liyang @ 2018-03-09  7:07 UTC (permalink / raw)
  To: Thomas Gleixner, Kees Cook, re.emese, Marc Zyngier; +Cc: linux-kernel

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.

^ permalink raw reply	[flat|nested] 2+ messages in thread
* Re: irqdesc: Why the "__ref" is needed in __irq_alloc_descs() ?
  2018-03-09  7:07 irqdesc: Why the "__ref" is needed in __irq_alloc_descs() ? Dou Liyang
@ 2018-03-09 11:39 ` Thomas Gleixner
  0 siblings, 0 replies; 2+ messages in thread
From: Thomas Gleixner @ 2018-03-09 11:39 UTC (permalink / raw)
  To: Dou Liyang; +Cc: Kees Cook, re.emese, Marc Zyngier, linux-kernel

On Fri, 9 Mar 2018, Dou Liyang wrote:
> 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.

See the various

#define irq_alloc_desc* 

variants. That will give you enough use cases from init.

> 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?

Well having code in a different section can cause performance issues, but
that only matters in a hotpath. irq_alloc_desc* is not performance critical
at all, so nothing to worry about.

Thanks,

	tglx

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-03-09 11:40 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
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2018-03-09  7:07 irqdesc: Why the "__ref" is needed in __irq_alloc_descs() ? Dou Liyang
2018-03-09 11:39 ` Thomas Gleixner

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