linux-kernel - Re: can someone explain "inline" once and for all?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 19 Jan 2007 15:13:55 +0100
From:	Adrian Bunk <bunk@...sta.de>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: can someone explain "inline" once and for all?

On Fri, Jan 19, 2007 at 03:01:44PM +0200, Pekka Enberg wrote:
> On 1/19/07, Robert P. J. Day <rpjday@...dspring.com> wrote:
> >is there a simple explanation for how to *properly* define inline
> >routines in the kernel?  and maybe this can be added to the
> >CodingStyle guide (he mused, wistfully).
> 
> AFAIK __always_inline is the only reliable way to force inlining where
> it matters for correctness (for example, when playing tricks with
> __builtin_return_address like we do in the slab).
> 
> Anything else is just a hint to the compiler that might be ignored if
> the optimizer thinks it knows better.

With the current implementation in the kernel (and considering that 
CONFIG_FORCED_INLINING was implemented in a way that it never had any 
effect), __always_inline and inline are currently equivalent.

__always_inline is mostly an annotation that really bad things might 
happen if the code doesn't get inlined.

But I'm not sure whether such a distinction is required at all - the 
rule of thumb should be that static functions in headers should be 
inline (otherwise, they belong into a C file), and functions in C files 
should never be marked inline. [1]

cu
Adrian

[1] For the latter there might be a handful of exceptions in the whole 
    kernel in real fastpath code, but usually gcc knows best when to 
    inline a function - and we have a global CONFIG_CC_OPTIMIZE_FOR_SIZE 
    knob for influencing the decision.

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/