Re: [PATCH] compiler: enable CONFIG_OPTIMIZE_INLINING forcibly

[Nick Desaulniers]

On Tue, Oct 1, 2019 at 10:55 AM Russell King - ARM Linux admin
<linux@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Oct 01, 2019 at 10:44:43AM -0700, Nick Desaulniers wrote:
> > I apologize; I don't mean to be difficult.  I would just like to avoid
> > surprises when code written with the assumption that it will be
> > inlined is not.  It sounds like we found one issue in arm32 and one in
> > arm64 related to outlining.  If we fix those two cases, I think we're
> > close to proceeding with Masahiro's cleanup, which I view as a good
> > thing for the health of the Linux kernel codebase.
>
> Except, using the C preprocessor for this turns the arm32 code into
> yuck:
>
> 1. We'd need to turn get_domain() and set_domain() into multi-line
>    preprocessor macro definitions, using the GCC ({ }) extension
>    so that get_domain() can return a value.
>
> 2. uaccess_save_and_enable() and uaccess_restore() also need to
>    become preprocessor macro definitions too.
>
> So, we end up with multiple levels of nested preprocessor macros.
> When something goes wrong, the compiler warning/error message is
> going to be utterly _horrid_.

That's why I preferred V1 of Masahiro's patch, that fixed the inline
asm not to make use of caller saved registers before calling a
function that might not be inlined.
-- 
Thanks,
~Nick Desaulniers