linux-kernel - Re: [PATCH] perf unwind: Limit warnings when asked for not supported unwind

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Date:   Mon, 19 Jun 2017 23:28:43 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     He Kuang <hekuang@...wei.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        David Ahern <dsahern@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH] perf unwind: Limit warnings when asked for not supported
 unwind

On Sun, Jun 18, 2017 at 08:01:38PM -0300, Arnaldo Carvalho de Melo wrote:
> Thanks!
> 
> On Jun 18, 2017 7:53 PM, "Jiri Olsa" <jolsa@...hat.com> wrote:
> 
> > On Fri, Jun 16, 2017 at 01:25:04PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Fri, Jun 16, 2017 at 02:12:53PM +0200, Jiri Olsa escreveu:
> > > > Ingo reported following warning flooding the report out:
> > > >
> > > >   unwind: target platform=x86 is not supported
> > > >
> > > > We trigger this warning when the dwarf unwinder is asked to
> > > > process architecture which wasn't compiled in, like when you
> > > > get 32bit application samples on your 64bit server and you
> > > > don't have the 32bit remote unwind support compiled in.
> > > >
> > > > This patch limits the warning to single message for arch,
> > > > and adds bits info. Above message is changed to:
> > > >
> > > >   unwind: target platform=x86 32bit is not supported
> > >
> > > Can we have a more informative message telling the user what is
> > > necessary to have this feature supported?
> > >
> > > The way you phrased it looks like it is not supported at all, while what
> > > I read in the discussion is that one needs to have specific versions of
> > > support libraries installed to have this working, right?
> >
> > exactly, I'll dig out from changelogs needed libunwind version
> > and change the changelog in v2

He Kuang,
could you please give me details on how to enable x86 remote unwind
on x86_64 server? can't find that in the libunwind's ./configure script

the feature tool detection example needs libunwind-x86.h header
and -lunwind-x86..  which is provided by libunwind-devel.i686 pkg,
but it conflicts with x86_64 libunwind-devel on fedora:

Error: Transaction check error:
  file /usr/include/libunwind.h from install of libunwind-devel-1.2-1.fc25.i686 conflicts with file from package libunwind-devel-1.2-1.fc25.x86_64

jirka