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SubjectRe: [PATCH][GIT PULL] tracing: add handler to trace_stat

On Wed, 25 Mar 2009, Frederic Weisbecker wrote:
> >
> > diff --git a/kernel/trace/trace_stat.h b/kernel/trace/trace_stat.h
> > index 202274c..f3546a2 100644
> > --- a/kernel/trace/trace_stat.h
> > +++ b/kernel/trace/trace_stat.h
> > @@ -12,7 +12,7 @@ struct tracer_stat {
> > /* The name of your stat file */
> > const char *name;
> > /* Iteration over statistic entries */
> > - void *(*stat_start)(void);
> > + void *(*stat_start)(struct tracer_stat *trace);
>
>
>
> In that case, shoudn't we pass another thing than the struct tracer_stat?
> Because nothing really private can be stored in it. Moreover, most of the
> time the handler is dedicated to this tracer_stat so it is able to have
> an access to it.
>
> May be we could add a void *private inside struct trace_stat and then pass
> it to stat_start() ?
>


Very few tracers need a private field so adding one would be a waste for
them. I just used the old container_of trick.


struct ftrace_profile_stat {
atomic_t disabled;
struct hlist_head *hash;
struct ftrace_profile_page *pages;
struct ftrace_profile_page *start;
struct tracer_stat stat;
};

static void *function_stat_start(struct tracer_stat *trace)
{
struct ftrace_profile_stat *stat =
container_of(trace, struct ftrace_profile_stat, stat);

[...]

And there you have it. I have everything I need unique to the tracer and
no need of a private pointer.

-- Steve



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