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From: Lukas Bulwahn <lukas.bulwahn@gmail.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Jann Horn <jannh@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>, Tom Rix <trix@redhat.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	kernel-janitors@vger.kernel.org,
	kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] zlib: define get_unaligned16() only when used
Date: Tue, 24 Nov 2020 13:00:30 +0100	[thread overview]
Message-ID: <CAKXUXMxfPqn4hG-QCtQM1qrK7Vck2hHRycb5VZBYHf4-ezkiGA@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a2rVKQ5UHzcycu=0QpjtSQ3Nne4Xre-7+V27vmCe9yfKg@mail.gmail.com>

On Tue, Nov 24, 2020 at 12:56 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig <hch@infradead.org> wrote:
> > On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > > pre-increment optimization"), get_unaligned16() is only used when
> > > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > > >
> > > > Hence, make CC=clang W=1 warns:
> > > >
> > > >   lib/zlib_inflate/inffast.c:20:1:
> > > >     warning: unused function 'get_unaligned16' [-Wunused-function]
> > > >
> > > > Define get_unaligned16() only when it is actually used.
> > > >
> > > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
> > >
> > > AFAICS a nicer option would be to "#include <asm/unaligned.h>" and
> > > then use "get_unaligned", which should automatically do the right
> > > thing everywhere and remove the need for defining get_unaligned16()
> > > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
> >
> > Yes, that is the right thing to do.
>
> It's possible that this didn't work when the code was originally added:
> The decompressor functions are called from the compressed boot path,
> which is a bit limited regarding which headers it can include, at least
> on some architectures.
>
> I would recommend test-building this for all architectures that include
> ../../../../lib/decompress_inflate.c from their boot code.
>

Jann, Christoph, Arnd, thanks for the advice. I will start to look
into this immediately.

Lukas

WARNING: multiple messages have this Message-ID (diff)
From: Lukas Bulwahn <lukas.bulwahn@gmail.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	Jann Horn <jannh@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>, Tom Rix <trix@redhat.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	kernel-janitors@vger.kernel.org,
	kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] zlib: define get_unaligned16() only when used
Date: Tue, 24 Nov 2020 12:00:30 +0000	[thread overview]
Message-ID: <CAKXUXMxfPqn4hG-QCtQM1qrK7Vck2hHRycb5VZBYHf4-ezkiGA@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a2rVKQ5UHzcycu=0QpjtSQ3Nne4Xre-7+V27vmCe9yfKg@mail.gmail.com>

On Tue, Nov 24, 2020 at 12:56 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Tue, Nov 24, 2020 at 12:51 PM Christoph Hellwig <hch@infradead.org> wrote:
> > On Tue, Nov 24, 2020 at 12:08:40PM +0100, Jann Horn wrote:
> > > > Since commit acaab7335bd6 ("lib/zlib: remove outdated and incorrect
> > > > pre-increment optimization"), get_unaligned16() is only used when
> > > > !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.
> > > >
> > > > Hence, make CC=clang W=1 warns:
> > > >
> > > >   lib/zlib_inflate/inffast.c:20:1:
> > > >     warning: unused function 'get_unaligned16' [-Wunused-function]
> > > >
> > > > Define get_unaligned16() only when it is actually used.
> > > >
> > > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
> > >
> > > AFAICS a nicer option would be to "#include <asm/unaligned.h>" and
> > > then use "get_unaligned", which should automatically do the right
> > > thing everywhere and remove the need for defining get_unaligned16()
> > > and checking CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS entirely?
> >
> > Yes, that is the right thing to do.
>
> It's possible that this didn't work when the code was originally added:
> The decompressor functions are called from the compressed boot path,
> which is a bit limited regarding which headers it can include, at least
> on some architectures.
>
> I would recommend test-building this for all architectures that include
> ../../../../lib/decompress_inflate.c from their boot code.
>

Jann, Christoph, Arnd, thanks for the advice. I will start to look
into this immediately.

Lukas

  reply	other threads:[~2020-11-24 12:01 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-24 10:40 [PATCH] zlib: define get_unaligned16() only when used Lukas Bulwahn
2020-11-24 10:40 ` Lukas Bulwahn
2020-11-24 11:08 ` Jann Horn
2020-11-24 11:08   ` Jann Horn
2020-11-24 11:50   ` Christoph Hellwig
2020-11-24 11:56     ` Arnd Bergmann
2020-11-24 11:56       ` Arnd Bergmann
2020-11-24 12:00       ` Lukas Bulwahn [this message]
2020-11-24 12:00         ` Lukas Bulwahn
2020-11-24 13:31       ` David Laight
2020-11-24 13:31         ` David Laight

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