linux-kernel - Re: [RFC][PATCH] tree-wide: Remove __inline__ and _

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Message-ID: <20181106194149.GC9761@hirez.programming.kicks-ass.net>
Date:   Tue, 6 Nov 2018 20:41:49 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        bp@...en8.de, namit@...are.com, joe@...ches.com,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        segher@...nel.crashing.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC][PATCH] tree-wide: Remove __inline__ and __inline usage

On Tue, Nov 06, 2018 at 11:18:59AM -0800, Linus Torvalds wrote:
> On Tue, Nov 6, 2018 at 2:02 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > Therefore I'm proposing to run:
> >
> >   git grep -l "\<__inline\(\|__\)\>" | while read file
> >   do
> >         sed -i -e 's/\<__inline\(\|__\)\>/inline/g' $file
> >   done
> >
> > On your current tree, and apply the below fixup patch on top of that
> > result.
> 
> So I started doing this, and in fact fixed up a few more issues by
> hand on top of your patch, but then realized hat it's somewhat
> dangerous and possibly broken.
> 
> For the uapi header files in particular, __inline__ may actually be
> required. Depending on use, and compiler settings, "inline" can be a
> word reserved for the user, and shouldn't be used by system headers.

*groan*, indeed. Now obvious those headers need to compile without our
override, so we could simply exclude uapi from the transformation.

(and __inline is mostly in staging/ and a few stray places, we really
should get rid of that one I feel, there's so few of them)

> But we *could* get rid of these two lines in include/linux/compiler_types.h
> 
>   #define __inline__ inline
>   #define __inline   inline
> 
> and just say that "inline" for the kernel means "always_inline", but
> if you use __inline__ or __inline then you get the "raw" compiler
> inlining.
> 
> Then people can decide to get rid of __inline__ on a case-by-case basis.

Right, that gets us what we need; but makes a fair bunch of kernel code
compile differently.

It probably doesn't matter, and a fair amount of the __inline__ usage is
in fairly crusty code which will likely never get fixed up.

And that is probably still a safer option than removing the #define
inline entirely.

Do you want me to do that patch, or have you already just done it?