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SubjectRe: [PATCH 2/4] tracing: add trace_export support for event trace
On Tue, 21 Jul 2020 12:37:33 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 20 Jul 2020 10:21:15 +0800
> Tingwei Zhang <tingwei@codeaurora.org> wrote:
>
> > Only function traces can be exported to other destinations currently.
> > This patch exports event trace as well.
> >
> > Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
> > ---
> > kernel/trace/trace.c | 24 +++++++++++++-----------
> > 1 file changed, 13 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index bb62269724d5..aef6330836e2 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -2697,17 +2697,6 @@ int tracepoint_printk_sysctl(struct ctl_table *table, int write,
> > return ret;
> > }
> >
> > -void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
> > -{
> > - if (static_key_false(&tracepoint_printk_key.key))
> > - output_printk(fbuffer);
> > -
> > - event_trigger_unlock_commit_regs(fbuffer->trace_file, fbuffer->buffer,
> > - fbuffer->event, fbuffer->entry,
> > - fbuffer->flags, fbuffer->pc, fbuffer->regs);
> > -}
> > -EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
> > -
>
> Please move the ftrace_exports routines up, instead of moving the
> trace_event_buffer_commit() down. As it fits better where it is (next
> to the other buffer_commit code).
>
> -- Steve
>
>
> > /*
> > * Skip 3:
> > *
> > @@ -2868,6 +2857,19 @@ int unregister_ftrace_export(struct
> > trace_export *export) }
> > EXPORT_SYMBOL_GPL(unregister_ftrace_export);
> >
> > +void trace_event_buffer_commit(struct trace_event_buffer *fbuffer)
> > +{
> > + if (static_key_false(&tracepoint_printk_key.key))
> > + output_printk(fbuffer);
> > +
> > + if (static_branch_unlikely(&ftrace_exports_enabled))
> > + ftrace_exports(fbuffer->event);

I would also recommend making each static branch a separate variable.
That way you could pick and choose what you want to enable. If you only
want events, and functions are being traced, it will add a bit of
overhead to handle the functions to just ignore them.

That is:

ftrace_exports_enabled, trace_event_exports_enabled,
trace_marker_exports_enabled.

-- Steve


> > + event_trigger_unlock_commit_regs(fbuffer->trace_file,
> > fbuffer->buffer,
> > + fbuffer->event, fbuffer->entry,
> > + fbuffer->flags, fbuffer->pc,
> > fbuffer->regs); +}
> > +EXPORT_SYMBOL_GPL(trace_event_buffer_commit);
> > +
> > void
> > trace_function(struct trace_array *tr,
> > unsigned long ip, unsigned long parent_ip, unsigned
> > long flags,
>

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