[lttng-dev] [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not set via debugfs

[Andi Kleen]

On Wed, Mar 12, 2014 at 08:47:07PM +0000, Mathieu Desnoyers wrote:
> ----- Original Message -----
> > From: "Andi Kleen" <andi at firstfloor.org>
> > To: "Mathieu Desnoyers" <mathieu.desnoyers at efficios.com>
> > Cc: "Steven Rostedt" <rostedt at goodmis.org>, "Frank Ch. Eigler" <fche at redhat.com>, linux-kernel at vger.kernel.org, "Ingo
> > Molnar" <mingo at kernel.org>, "Frederic Weisbecker" <fweisbec at gmail.com>, "Andrew Morton" <akpm at linux-foundation.org>,
> > "Johannes Berg" <johannes.berg at intel.com>, "Linus Torvalds" <torvalds at linux-foundation.org>, "Peter Zijlstra"
> > <peterz at infradead.org>, "Thomas Gleixner" <tglx at linutronix.de>, "Greg Kroah-Hartman" <gregkh at linuxfoundation.org>,
> > "lttng-dev" <lttng-dev at lists.lttng.org>, "Rusty Russell" <rusty at rustcorp.com.au>, "Andi Kleen" <andi at firstfloor.org>
> > Sent: Wednesday, March 12, 2014 4:35:15 PM
> > Subject: Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not set via debugfs
> > 
> > > So I understand that you wish to banish tracepoints from static inline
> > > functions within headers to ensure they only appear within a single module.
> > > This seems to be a step backward, but let's assume we stick to that rule.
> > > Then how do you envision dealing with Link-Time Optimisations (LTO) ?
> > 
> > I assume it uses the file name defines set by Kbuild?
> 
> Just to make sure I understand your question: I understand that you are asking
> whether tracepoints use file name defines at all in the naming of a tracepoint.
> The answer to this question is: No, they do not.

Ok. It uses kallsyms? That can change of course.
> 
> > These don't change with
> > LTO. It's whatever was specified at compile time. Also LTO doesn't
> > inline over module boundaries (if the module is not built in)
> 
> Good to know. Can it inline core kernel functions into a module ?

Each module and the main kernel are currently LTO'ed separately.

In theory it would be possible to change this, but likely at some
compile time cost.

-Andi