linux-kernel - Re: [PATCHv2 08/11] atomics: switch to generated fallbacks

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Message-ID: <20180704160145.kyzzymyufv3kt52l@lakrids.cambridge.arm.com>
Date:   Wed, 4 Jul 2018 17:01:46 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        boqun.feng@...il.com
Subject: Re: [PATCHv2 08/11] atomics: switch to generated fallbacks

On Wed, Jul 04, 2018 at 04:28:47PM +0100, Will Deacon wrote:
> On Mon, Jun 25, 2018 at 11:59:49AM +0100, Mark Rutland wrote:
> > As a step to ensuring the atomic* APIs are consistent, switch to fallbacks
> > generated by gen-atomic-fallback.sh.
> > 
> > These are checked in rather than generated with Kbuild, since:
> > 
> > * This allows inspection of the atomics with git grep and ctags on a
> >   pristine tree, which Linus strongly prefers being able to do.
> > 
> > * The fallbacks are not expected to change very often, and are not
> >   affected by machine details or configuration options, so regenerating
> >   them for *every* build is somewhat wasteful.
> > 
> > * These are included by files required *very* early in the build process
> >   (e.g. for generating bounds.h), and we'd rather not complicate the
> >   top-level Kbuild file.
> 
> Would it be worth checking that the generated output from the script doesn't
> differ from the file in tree at some point during the build, and issuing a
> warning if they do?

We could do that in the top-level Kbuild file. It would be less hideous
than the generation was, since we don't have to add dependencies to all
other targets.

I can take a look, if you'd like?

Thanks,
Mark.