svn commit: r354095 - in head/sys: amd64/amd64 amd64/include kern

[Antoine Brodin]

On Sat, Oct 26, 2019 at 10:27 AM Konstantin Belousov
<kostikbel at gmail.com> wrote:
> On Sat, Oct 26, 2019 at 08:24:09AM +0200, Antoine Brodin wrote:
> > On Fri, Oct 25, 2019 at 10:09 PM Konstantin Belousov <kib at freebsd.org> wrote:
> > >
> > > Author: kib
> > > Date: Fri Oct 25 20:09:42 2019
> > > New Revision: 354095
> > > URL: https://svnweb.freebsd.org/changeset/base/354095
> > >
> > > Log:
> > >   amd64: move pcb out of kstack to struct thread.
> > >
> > >   This saves 320 bytes of the precious stack space.
> > >
> > >   The only negative aspect of the change I can think of is that the
> > >   struct thread increased by 320 bytes obviously, and that 320 bytes are
> > >   not swapped out anymore. I believe the freed stack space is much more
> > >   important than that.  Also, current struct thread size is 1392 bytes
> > >   on amd64, so UMA will allocate two thread structures per (4KB) slab,
> > >   which leaves a space for pcb without increasing zone memory use.
> > >
> > >   Reviewed by:  alc, markj
> > >   Tested by:    pho
> > >   Sponsored by: The FreeBSD Foundation
> > >   MFC after:    2 weeks
> > >   Differential revision:        https://reviews.freebsd.org/D22138
> >
> > Hi,
> >
> > It seems that this breaks at least some versions of gcc:
> >
> > In file included from /usr/include/sys/proc.h:75,
> >                  from /usr/include/sys/user.h:51,
> >                  from ./md-unwind-support.h:34,
> >                  from
> > /wrkdirs/usr/ports/lang/gcc10-devel/work/gcc-10-20191020/libgcc/unwind-dw2.c:412:
> > /usr/include/machine/proc.h:76:13: error: field 'md_pcb' has incomplete type
> >    76 |  struct pcb md_pcb;
> >       |             ^~~~~~
> >
>
> It is very strange.  Are gcc 9 or 8 affected ?

gcc 8 and 9 are affected too.

> As a blind guess, please try this patch.
>
> diff --git a/sys/amd64/include/pcb.h b/sys/amd64/include/pcb.h
> index 44e34fa5c83..9758e684da2 100644
> --- a/sys/amd64/include/pcb.h
> +++ b/sys/amd64/include/pcb.h
> @@ -45,7 +45,7 @@
>  #include <machine/fpu.h>
>  #include <machine/segments.h>
>
> -#ifdef __amd64__
> +#if defined(__amd64__) || defined(__x86_64__)
>  /*
>   * NB: The fields marked with (*) are used by kernel debuggers.  Their
>   * ABI should be preserved.

I will test this.

Antoine