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Sat, 06 Jul 2024 06:51:01 -0700 (PDT) MIME-Version: 1.0 References: <20240702234008.19101-1-richard.weiyang@gmail.com> <20240702234008.19101-2-richard.weiyang@gmail.com> <20240705065456.dogycpd37jun44p5@master> <20240706061236.snp4r2tixx3h7hfe@master> In-Reply-To: <20240706061236.snp4r2tixx3h7hfe@master> From: Masahiro Yamada Date: Sat, 6 Jul 2024 22:50:25 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/3] modpost: .meminit.* is not in init section when CONFIG_MEMORY_HOTPLUG set To: Wei Yang Cc: akpm@linux-foundation.org, nathan@kernel.org, nicolas@fjasle.eu, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, Mike Rapoport Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 77phh43zis91fp4o7tuuafr7spiam4wh X-Rspam-User: X-Rspamd-Queue-Id: 23C2A1A0011 X-Rspamd-Server: rspam02 X-HE-Tag: 1720273866-770643 X-HE-Meta: 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 +k9nPRwK 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Jul 6, 2024 at 3:12=E2=80=AFPM Wei Yang = wrote: > > On Fri, Jul 05, 2024 at 06:54:56AM +0000, Wei Yang wrote: > >On Wed, Jul 03, 2024 at 11:44:38PM +0900, Masahiro Yamada wrote: > >>On Wed, Jul 3, 2024 at 8:40=E2=80=AFAM Wei Yang wrote: > >>> > >>> .meminit.* is not put into init section when CONFIG_MEMORY_HOTPLUG is > >>> set, since we define MEM_KEEP()/MEM_DISCARD() according to > >>> CONFIG_MEMORY_HOTPLUG. > >>> > >>> Signed-off-by: Wei Yang > >>> CC: Mike Rapoport (IBM) > >>> --- > >>> scripts/mod/modpost.c | 10 ++++++++++ > >>> 1 file changed, 10 insertions(+) > >> > >> > >> > >>NACK. > >> > >> > >>The section mismatch is performed _unconditionally_. > >> > >> > >> > >>In the old days, we did this depending on relevant CONFIG options. > >>It was more than 15 years ago that we stopped doing that. > >> > >> > >>See this: > >> > >> > >>commit eb8f689046b857874e964463619f09df06d59fad > >>Author: Sam Ravnborg > >>Date: Sun Jan 20 20:07:28 2008 +0100 > >> > >> Use separate sections for __dev/__cpu/__mem code/data > >> > >> > >> > >> > >>So, if you wanted to check this only when CONFIG_MEMORY_HOTPLUG=3Dn, > >>you would need to add #ifdef CONFIG_MEMORY_HOTPLUG to include/linux/ini= t.h > >> > >>That is what we did in the Linux 2.6.* era, which had much worse > >>section mismatch coverage. > >> > > > >Masahiro > > > >If you would give me some suggestions, I'd appreciate it a lot. > > > >The original thing I want to do is to put function __free_pages_core() i= n > >__meminit section, since this function is only used by __init functions = and > >in memory_hotplug.c. This means it is save to release it if > >CONFIG_MEMORY_HOTPLUG is set. > > > >Then I add __meminit to function __free_pages_core() and face the warnin= g from > >modpost. > > > > WARNING: modpost: vmlinux: section mismatch in reference: generic_onli= ne_page+0xa (section: .text) -> __free_pages_core (section: .meminit.text) > > > >A .text function calls init code is not proper. Then I add __meminit to > >generic_online_page too. Then I face this warning from modpost. > > > > WARNING: modpost: vmlinux: generic_online_page: EXPORT_SYMBOL used for= init symbol. Remove __init or EXPORT_SYMBOL. > > > > I guess I found the correct way. > > Add __ref to generic_online_page to not issue a warning. Yes, __ref is used to bypass the section mismatch check. Some functions in mm/memory_hotplug.c are annotated as __ref to reference __meminit functions. Adding __ref is the easy solution. Having said that, I started to think eb8f689046b857874e964463619f09df06d59fad was the wrong decision. I will revert it. --=20 Best Regards Masahiro Yamada