linux-kernel - Re: [PATCH RFC] sched/headers: Fix sched_setattr userspace compilation issues

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Message-ID: <20200522133816.GB210175@google.com>
Date:   Fri, 22 May 2020 09:38:16 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Matthew Blecker <matthewb@...gle.com>,
        Jesse Barnes <jsbarnes@...gle.com>,
        Mike Frysinger <vapier@...gle.com>,
        Christian Brauner <christian@...uner.io>,
        Vineeth Remanan Pillai <vpillai@...italocean.com>,
        vineethrp@...il.com, Peter Zijlstra <peterz@...radead.org>,
        stable <stable@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH RFC] sched/headers: Fix sched_setattr userspace
 compilation issues

On Fri, May 22, 2020 at 03:13:55PM +0200, Christian Brauner wrote:
> On Thu, May 21, 2020 at 11:55:21AM -0400, Joel Fernandes wrote:
> > On Thu, May 21, 2020 at 11:53 AM Joel Fernandes (Google)
> > <joel@...lfernandes.org> wrote:
> > >
> > > On a modern Linux distro, compiling the following program fails:
> > >  #include<stdlib.h>
> > >  #include<stdint.h>
> > >  #include<pthread.h>
> > >  #include<linux/sched/types.h>
> > >
> > >  void main() {
> > >          struct sched_attr sa;
> > >
> > >          return;
> > >  }
> > >
> > > with:
> > > /usr/include/linux/sched/types.h:8:8: \
> > >                         error: redefinition of ‘struct sched_param’
> > >     8 | struct sched_param {
> > >       |        ^~~~~~~~~~~
> > > In file included from /usr/include/x86_64-linux-gnu/bits/sched.h:74,
> > >                  from /usr/include/sched.h:43,
> > >                  from /usr/include/pthread.h:23,
> > >                  from /tmp/s.c:4:
> > > /usr/include/x86_64-linux-gnu/bits/types/struct_sched_param.h:23:8:
> > > note: originally defined here
> > >    23 | struct sched_param
> > >       |        ^~~~~~~~~~~
> > >
> > > This is also causing a problem on using sched_attr Chrome. The issue is
> > > sched_param is already provided by glibc.
> > >
> > > Guard the kernel's UAPI definition of sched_param with __KERNEL__ so
> > > that userspace can compile.
> > >
> > > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > 
> > If it is more preferable, another option is to move sched_param to
> > include/linux/sched/types.h
> 
> Might it be worth Ccing libc-alpha here? Seems like one of those classic
> header conflicts.

sched_param is defined by POSIX from my reading of the manpage. Is the kernel
supposed to define it in the UAPI at all? I guarded it with __KERNEL__ as you
can see.

Resent with libc-alpha CC'd per your suggestion.

thanks,

 - Joel