From: Johan Hovold <johan@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Johan Hovold <johan@kernel.org>, Jessica Yu <jeyu@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>,
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
Date: Fri, 6 Nov 2020 18:02:27 +0100 [thread overview]
Message-ID: <20201106170227.GE4085@localhost> (raw)
In-Reply-To: <20201106115523.41f7e2ed@gandalf.local.home>
On Fri, Nov 06, 2020 at 11:55:23AM -0500, Steven Rostedt wrote:
> On Fri, 6 Nov 2020 17:45:37 +0100
> Johan Hovold <johan@kernel.org> wrote:
>
> > It's simply specifying alignment when declaring the variable that
> > prevents this optimisation. The relevant code is in the function
> > align_variable() in [1] where DATA_ALIGNMENT() is never called in case
> > an alignment has been specified (!DECL_USER_ALIGN(decl)).
> >
> > There's no mention in the documentation of this that I'm aware of, but
> > this is the way the aligned attribute has worked since its introduction
> > judging from the commit history.
> >
> > As mentioned above, we've been relying on this for kernel parameters and
> > other structures since 2003-2004 so if it ever were to change we'd find
> > out soon enough.
> >
> > It's about to be used for scheduler classes as well. [2]
>
> Is this something that gcc folks are aware of? Yes, we appear to be relying
> on undocumented implementations, but that hasn't caused gcc to break the
> kernel in the past.
The scheduler change was suggested by Jakub so at least some of them
are.
Johan
next prev parent reply other threads:[~2020-11-06 17:02 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 17:57 [PATCH 0/8] linker-section array fix and clean ups Johan Hovold
2020-11-03 17:57 ` [PATCH 1/8] of: fix linker-section match-table corruption Johan Hovold
2020-11-03 17:57 ` [PATCH 2/8] earlycon: simplify earlycon-table implementation Johan Hovold
2020-11-03 17:57 ` [PATCH 3/8] module: drop version-attribute alignment Johan Hovold
2020-11-03 17:57 ` [PATCH 4/8] module: simplify version-attribute handling Johan Hovold
2020-11-03 17:57 ` [PATCH 5/8] init: use type alignment for kernel parameters Johan Hovold
2020-11-03 17:57 ` [PATCH 6/8] params: drop redundant "unused" attributes Johan Hovold
2020-11-03 17:57 ` [PATCH 7/8] params: use type alignment for kernel parameters Johan Hovold
2020-11-03 17:57 ` [PATCH 8/8] params: clean up module-param macros Johan Hovold
2020-11-04 9:16 ` get_maintainer.pl bug? (was: Re: [PATCH 0/8] linker-section array fix and clean ups) Johan Hovold
2020-11-04 12:04 ` Joe Perches
2020-11-04 15:31 ` Johan Hovold
2020-11-06 16:03 ` [PATCH 0/8] linker-section array fix and clean ups Jessica Yu
2020-11-06 16:45 ` Johan Hovold
2020-11-06 16:55 ` Steven Rostedt
2020-11-06 17:02 ` Johan Hovold [this message]
2020-11-11 15:47 ` Jessica Yu
2020-11-13 14:18 ` Johan Hovold
2020-11-23 10:39 ` Johan Hovold
2020-11-25 14:51 ` Jessica Yu
2020-11-27 9:59 ` Johan Hovold
2020-12-01 9:55 ` Jessica Yu
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