linux-kernel - Re: [musl] [PATCH 1/1] uapi: Don't include <linux/sysinfo.h> in <linux/kernel.h>

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Date:   Thu, 1 Oct 2020 17:52:13 -0400
From:   Rich Felker <dalias@...ifal.cx>
To:     Petr Vorel <petr.vorel@...il.com>
Cc:     linux-kernel@...r.kernel.org, musl@...ts.openwall.com,
        linux-api@...r.kernel.org, libc-alpha@...rceware.org,
        Peter Korsgaard <peter@...sgaard.com>,
        Florian Weimer <fweimer@...hat.com>,
        Baruch Siach <baruch@...s.co.il>,
        "David S . Miller" <davem@...emloft.net>,
        Michal Kubecek <mkubecek@...e.cz>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [musl] [PATCH 1/1] uapi: Don't include <linux/sysinfo.h> in
 <linux/kernel.h>

On Thu, Oct 01, 2020 at 10:27:03PM +0200, Petr Vorel wrote:
> Hi Rich,
> 
> > On Thu, Oct 01, 2020 at 09:52:31PM +0200, Petr Vorel wrote:
> > > + update code where needed (include <linux/sysinfo.h> in code which
> > > included <linux/kernel.h> only to get struct sysinfo or SI_LOAD_SHIFT).
> 
> > > The reason is to avoid indirect <linux/sysinfo.h> include when using
> > > some network headers: <linux/netlink.h> or others [1] ->
> > > <linux/kernel.h> -> <linux/sysinfo.h>.
> 
> > > This indirect include causes redefinition of struct sysinfo when
> > > included both <sys/sysinfo.h> and some of network headers:
> 
> > > In file included from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/kernel.h:5,
> > >                  from x86_64-buildroot-linux-musl/sysroot/usr/include/linux/netlink.h:5,
> > >                  from ../include/tst_netlink.h:14,
> > >                  from tst_crypto.c:13:
> > > x86_64-buildroot-linux-musl/sysroot/usr/include/linux/sysinfo.h:8:8: error: redefinition of ‘struct sysinfo’
> > >  struct sysinfo {
> > >         ^~~~~~~
> > > In file included from ../include/tst_safe_macros.h:15,
> > >                  from ../include/tst_test.h:93,
> > >                  from tst_crypto.c:11:
> > > x86_64-buildroot-linux-musl/sysroot/usr/include/sys/sysinfo.h:10:8: note: originally defined here
> 
> > > [1] or <linux/sysctl.h>, <linux/ethtool.h>, <linux/mroute6.h>, <linux/ethtool.h>
> 
> > > Suggested-by: Rich Felker <dalias@...ifal.cx>
> > > Signed-off-by: Petr Vorel <petr.vorel@...il.com>
> > > ---
> > > Hi,
> 
> > > this looks to be long standing problem: python-psutil [2], iproute2 [3],
> > > even for glibc in the past [4] and it tried to be solved before [5].
> 
> > > This will require glibc fix after:
> 
> > You can't do this; it breaks the existing contract with glibc. New
> > kernel headers can't force a glibc upgrade.
> Right, got that.
> 
> > You just have to get rid
> > of use of <linux/kernel.h> elsewhere in the uapi headers. It was a
> > mistake that <linux/sysinfo.h> was ever separated out of
> > <linux/kernel.h> since it didn't (and couldn't) fix the contract that
> > <linux/kernel.h> exposes struct sysinfo (and that it's misnamed). But
> > it's no big deal. This can all be fixed without any breakage anywhere
> > just by not using it.
> Back to your original suggestion to move the alignment macros to a separate
> header. I was trying to avoid it not sure if introducing new header is
> acceptable, but we'll see.

Isn't there already another similar header with that type of macro
that they belong in?

Rich