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Date:   Fri, 13 Nov 2020 15:18:36 +0100
From:   Johan Hovold <johan@kernel.org>
To:     Jessica Yu <jeyu@kernel.org>
Cc:     Johan Hovold <johan@kernel.org>, linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Nick Desaulniers <ndesaulniers@gooogle.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        David Miller <davem@davemloft.net>,
        Jakub Jelinek <jakub@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Daniel Kurtz <djkurtz@chromium.org>,
        linux-arch@vger.kernel.org, linux-m68k@lists.linux-m68k.org
Subject: Re: [PATCH 0/8] linker-section array fix and clean ups
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References: <20201103175711.10731-1-johan@kernel.org>
 <20201106160344.GA12184@linux-8ccs.fritz.box>
 <20201106164537.GD4085@localhost>
 <20201111154716.GB5304@linux-8ccs>
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On Wed, Nov 11, 2020 at 04:47:16PM +0100, Jessica Yu wrote:

> Thanks for providing the links and references. Your explanation and
> this reply from Jakub [1] clarified things for me. I was not aware of
> the distinction gcc made between aligned attributes on types vs. on
> variables. So from what I understand now, gcc suppresses the
> optimization when the alignment is specified in the variable
> declaration, but not necessarily when the aligned attribute is just on
> the type.
> 
> Even though it's been in use for a long time, I think it would be
> really helpful if this gcc quirk was explained just a bit more in the
> patch changelogs, especially since this is undocumented behavior.
> I found the explanation in [1] (as well as in your cover letter) to be
> sufficient. Maybe something like "GCC suppresses any optimizations
> increasing alignment when the alignment is specified in the variable
> declaration, as opposed to just on the type definition. Therefore,
> explicitly specify type alignment when declaring entries to prevent
> gcc from increasing alignment."

Sure, I can try to expand the commit messages a bit.

> In any case, I can take the module and moduleparam.h patches through
> my tree, but I will wait a few days in case there are any objections.

Sounds good, thanks. I'll send a v2 next week then.

Johan

> [1] https://lore.kernel.org/lkml/20201021131806.GA2176@tucnak/