[lttng-dev] Debian specific userspace RCU configure override

[Jon Bernard]

* Thibault, Daniel <Daniel.Thibault at drdc-rddc.gc.ca> wrote:
> ----------------------------------------------------------------------
> Date: Wed, 28 May 2014 14:10:50 -0400
> 
> > As I currently understand, the debian build problem is that although the
> > package is compiled on armv7 hardware, it is expected to target armv4t.
> > And this is not correctly detected at configure-time.  The folks on
> > #debian-arm suggested that this could be solved in configure.ac.  I can
> > explicitly pass '--build <target>' to ./configure to get around this,
> > but arm users that build from source will need to remember this.
> >
> > Jon
> ----------------------------------------------------------------------
>    I need to revive this thread.  Although the original build failure
>    may have been on ARMv7 wanting ARMv4, I've run into the same
>    failure with a pure ARMv7 architecture.  Specifically, Beagle Bone
>    Black.
> 
>    I built userspace-rcu without trouble (except for that clock
>    business reported earlier), but when I then tried to build
>    lttng-ust, I ran into the same 'Error: selected processor does not
>    support ARM mode `dmb'.  Taking a look at the userspace-rcu and
>    lttng-ust config.logs, they *both* report 'uname -m = armv7l'.  The
>    core tests *both* report a build system type of
>    'armv7l-unknown-linux-gnueabi'.  However, userspace-rcu tests for
>    dmb and finds it, while lttng-ust omits this test.
> 
>    The make error occurs during the CCLD of libringbuffer.la.
> 
>    Besides the make, config and configure logs, what should I post
>    here?

It sounds like you might be hitting the same issue that I had.  When
building urcu on this particular host, ./configure will detect an armv7
target even though userland is armv4.  I was able to get around this by
explicitly passing '--build' and '--host' flags to configure.  There is
also a pre-built armel deb for the latest version of urcu at:

    https://packages.debian.org/sid/armel/liburcu2/download

In my particular case, the build machine is v7 hardware running a v7
kernel but with a v4 userland.  You can confirm this with

    gcc -dumpmachine

Maybe this will help, I'm curious to know how it goes.

Cheers,

-- 
Jon