[lttng-dev] Debian specific userspace RCU configure override

[Jon Bernard]

* Mathieu Desnoyers <mathieu.desnoyers at efficios.com> wrote:
> ----- Original Message -----
> > From: "Jon Bernard" <jbernard at debian.org>
> > To: "Ondřej Surý" <ondrej at sury.org>
> > Cc: "Mathieu Desnoyers" <mathieu.desnoyers at efficios.com>, "Michael Jeanson" <mjeanson at efficios.com>, "lttng-dev"
> > <lttng-dev at lists.lttng.org>
> > Sent: Tuesday, May 27, 2014 4:18:48 PM
> > Subject: Re: Debian specific userspace RCU configure override
> > 
> > * Ondřej Surý <ondrej at sury.org> wrote:
> > > On Sun, May 25, 2014, at 2:59, Mathieu Desnoyers wrote:
> > > > Why are each package compiled against completely different targets ?
> > > 
> > > urcu invokes ./configure manually while ltt-control uses
> > > dh_auto_configure wrapper and that makes the difference
> > 
> > This is correct.  When I first saw the difference, I assumed they would
> > both invoke configure in a way that wouldn't effect the target.  But now
> > I remember having a similar problem on sparc (which is why urcu includes
> > this override) where the target discovery was not correct.
> > 
> > It looks to me like a bug related to debhelper (which provides
> > dh_auto_configure).  For now, I think this override applied to
> > lttng-tools will correctly fix the build without disabling dmb.  I will
> > let the existing transition into testing complete and then submit new
> > packages.
> 
> The big question here: is it OK to generate "dmb" instruction ? If the
> intent of this architecture support is to cover earlier-than-armv7 ARM
> processors, then "dmb" should not be explicitly generated, and therefore
> URCU configuration would need fixing. If the intent of this Debian arch
> is to cover only ARMv7 and better, then it's lttng-tools that needs
> fixing.

I was assuming the latter, that only ARMv7 and better would be covered,
but this is a very good point and I will seek clarification before
I make any changes.  I will let you know what I find out.

-- 
Jon