Re: [PATCH v3] ftrace: add a tracepoint for __raise_softirq_irqoff()

Steven Rostedt
2009-05-11T14:53:19Z

On Mon, 11 May 2009, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@goodmis.org) wrote:
> >
> > On Mon, 11 May 2009, Mathieu Desnoyers wrote:
> > >
> > > Yes, we should try to fix TRACE_EVENT, but we should fix it _before_ we
> > > start using it widely. Circular header dependencies is a real problem
> > > with TRACE_EVENT right now.
> > >
> > > Until we fix this, I will be tempted to stay with a known-good solution,
> > > which is DECLARE/DEFINE_TRACE.
> >
> > The majority of tracepoints happen is C files. Those few cases where they
> > are used in headers is where the issues arise.
> >
> > But...
> >
> > I did not want to uglify all trace event headers with:
> >
> > #ifdef CREATE_FOO_TRACE_POINTS
> > #undef CREATE_FOO_TRACE_POINTS
> > #include <trace/define_trace.h>
> > #endif
> >
> > We would only need to do that for those trace points that need to be
> > included in header files. Then the declaration C file would need to define
> > both CREATE_FOO_TRACE_POINTS and CREATE_TRACE_POINTS
> >
> > #define CREATE_FOO_TRACE_POINTS
> > #define CRATE_TRACE_POINTS
> > #include <trace/events/foo.h>
> >
> >
> > But this is pretty trivial to solve, and I do not consider it a show
> > stopper or a major header dependency problem.
> >
> > -- Steve
> >
>
> Hrm, is there any way to solve it elegantly ?
>
> What we really need is to see the cases where TRACE_EVENT() is used as a
> declaration vs the case where it expands
> TP_STRUCT__entry/TP_fast_assign/TP_printk as having different
> dependencies. The problem comes when we bring the include dependencies
> of the TP_fast_assign part into the tracepoint header and it becomes
> a dependency of the TRACE_EVENT() declaration-only part.
>
> Can we do the following ?
>
> All tracepoint headers could surround the include dependencies by :
>
> #ifdef BUILD_EVENTS
> #include <veryannoyingheaderdependency.h>
> #endif
>
> And then we follow this by the TRACE_EVENT() declarations.
>
> BUILD_EVENTS would only be defined in kernel/trace/events.c.

That file no longer exists. All the events are created with the
define_trace.h or ftrace.h file.

We could do something like your

#ifdef BUILD_EVENTS /* or better name BUILDING_EVENTS ?? */
#include <allmyannoyingheaders.h>
[...]
#endif

And then have the define_trace.h file add define it. But this again adds
more annoying CPP commands to all trace_event headers.

-- Steve

>
> I think it should work, but it looks a bit too simple, so I may have
> missed something... ?
>
> Mathieu
>
>
> --
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
>