linux-kernel - Re: [PATCH 7/7] context_tracking: Always inline empty stubs

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Message-ID: <Yo+cFQkX9fVTOmrv@FVFF77S0Q05N.cambridge.arm.com>
Date:   Thu, 26 May 2022 16:26:13 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        elver@...gle.com, jbaron@...mai.com, rostedt@...dmis.org,
        ardb@...nel.org
Subject: Re: [PATCH 7/7] context_tracking: Always inline empty stubs

On Thu, May 26, 2022 at 08:16:54AM -0700, Josh Poimboeuf wrote:
> On Thu, May 26, 2022 at 04:10:52PM +0100, Mark Rutland wrote:
> > On Thu, May 26, 2022 at 08:02:06AM -0700, Josh Poimboeuf wrote:
> > > On Thu, May 26, 2022 at 12:52:59PM +0200, Peter Zijlstra wrote:
> > > > Because GCC is seriously challenged..
> > > 
> > > Or are these CONFIG_DEBUG_SECTION_MISMATCH?
> > 
> > Does it matter?
> 
> Yes, because I believe the only thing this option is good for is
> creating a bunch of useless '__always_inline' patches:
> 
>   https://lore.kernel.org/all/7fad83ecde03540e65677959034315f8fbb3755e.1649434832.git.jpoimboe@redhat.com/

Sure, but as I said, there are other reasons why the compiler can generate code
in this way, even if that's unlikely. Without `__always_inline` we don't
actually have a guarantee of inlining, so those warning *is* legitimate, even
if 99.99% of the time the compiler doesn't decide to generate code in a silly
way.

Thanks,
Mark.