Re: [tip:perf/urgent] tracing: Include module.h in define_trace.h

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 2011-01-10 at 14:49 +0100, Peter Zijlstra wrote:
> After I got everything building on that tree I was working on, the above
> was found to compile but not to link, since it makes every:
> 
>  #define CREATE_TRACE_POINTS
>  #include <trace/event/foo.h>
> 
> site also create the trace/event/module.h tracepoints, thus confusing
> the linker with tons of duplicate symbols.
> 
> The below patch makes things compile and link:
> 
> ---
>  include/trace/define_trace.h |   23 +++++++++++++----------
>  1 files changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
> index da39b22..9ebd0d3 100644
> --- a/include/trace/define_trace.h
> +++ b/include/trace/define_trace.h
> @@ -21,16 +21,6 @@
>  #undef CREATE_TRACE_POINTS

But here we undefine CREATE_TRACE_POINTS, why would this cause a problem
in module.h?

-- Steve

>  
>  #include <linux/stringify.h>
> -/*
> - * module.h includes tracepoints, and because ftrace.h
> - * pulls in module.h:
> - *  trace/ftrace.h -> linux/ftrace_event.h -> linux/perf_event.h ->
> - *  linux/ftrace.h -> linux/module.h
> - * we must include module.h here before we play with any of
> - * the TRACE_EVENT() macros, otherwise the tracepoints included
> - * by module.h may break the build.
> - */
> -#include <linux/module.h>
>  
>  #undef TRACE_EVENT
>  #define TRACE_EVENT(name, proto, args, tstruct, assign, print)	\
> @@ -120,4 +110,17 @@
>  /* We may be processing more files */
>  #define CREATE_TRACE_POINTS
>  
> +#else /* CREATE_TRACE_POINTS */
> +
> +/*
> + * module.h includes tracepoints, and because ftrace.h
> + * pulls in module.h:
> + *  trace/ftrace.h -> linux/ftrace_event.h -> linux/perf_event.h ->
> + *  linux/ftrace.h -> linux/module.h
> + * we must include module.h here before we play with any of
> + * the TRACE_EVENT() macros, otherwise the tracepoints included
> + * by module.h may break the build.
> + */
> +#include <linux/module.h>
> +
>  #endif /* CREATE_TRACE_POINTS */