linux-kernel - Re: [PATCH v1] PM: runtime: add tracepoint for runtime

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Date: Wed, 21 Feb 2024 09:57:03 -0800
From: Vilas Bhat <vilasbhat@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Saravana Kannan <saravanak@...gle.com>, 
	kernel-team@...roid.com, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v1] PM: runtime: add tracepoint for runtime_status changes

On Wed, Feb 21, 2024 at 9:12 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 21 Feb 2024 16:41:10 +0000
> Vilas Bhat <vilasbhat@...gle.com> wrote:
>
>
> > diff --git a/include/trace/events/rpm.h b/include/trace/events/rpm.h
> > index 3c716214dab1..f1dc4e95dbce 100644
> > --- a/include/trace/events/rpm.h
> > +++ b/include/trace/events/rpm.h
> > @@ -101,6 +101,42 @@ TRACE_EVENT(rpm_return_int,
> >               __entry->ret)
> >  );
> >
> > +#define RPM_STATUS_STRINGS \
> > +     { RPM_INVALID, "RPM_INVALID" }, \
> > +     { RPM_ACTIVE, "RPM_ACTIVE" }, \
> > +     { RPM_RESUMING, "RPM_RESUMING" }, \
> > +     { RPM_SUSPENDED, "RPM_SUSPENDED" }, \
> > +     { RPM_SUSPENDING, "RPM_SUSPENDING" }
> > +
> > +/*
> > + * ftrace's __print_symbolic requires that all enum values be wrapped in the
> > + * TRACE_DEFINE_ENUM macro so that the enum value can be encoded in the ftrace
> > + * ring buffer.
> > + */
> > +TRACE_DEFINE_ENUM(RPM_INVALID);
> > +TRACE_DEFINE_ENUM(RPM_ACTIVE);
> > +TRACE_DEFINE_ENUM(RPM_RESUMING);
> > +TRACE_DEFINE_ENUM(RPM_SUSPENDED);
> > +TRACE_DEFINE_ENUM(RPM_SUSPENDING);
>
> You could do what everyone else does:
>
> #define RPM_STATUS_STRINGS                      \
>         EM( RPM_INVALID, "RPM_INVALID" )        \
>         EM( RPM_ACTIVE, "RPM_ACTIVE" )          \
>         EM( RPM_RESUMING, "RPM_RESUMING" )      \
>         EM( RPM_SUSPENDED, "RPM_SUSPENDED" )    \
>         EMe( RPM_SUSPENDING, "RPM_SUSPENDING" )
>
> #undef EM
> #undef EMe
> #define EM(a, b)        TRACE_DEFINE_ENUM(a);
> #define EMe(a, b)       TRACE_DEFINE_ENUM(a);
>
> RPM_STATUS_STRINGS
>
> #undef EM
> #undef EMe
> #define EM(a, b)        { a, b },
> #define EMe(a, b)       { a, b }
>

Thanks for the comment, Steven. I did notice both methods of defining
enum values for tracepoints and chose this method because it felt
clearer. Could you clarify on why the method you suggested is
preferred?

> > +
> > +TRACE_EVENT(rpm_status,
> > +     TP_PROTO(struct device *dev, enum rpm_status status),
> > +     TP_ARGS(dev, status),
> > +
> > +     TP_STRUCT__entry(
> > +             __string(name,  dev_name(dev))
> > +             __field(int,    status)
> > +     ),
> > +
> > +     TP_fast_assign(
> > +             __assign_str(name, dev_name(dev));
> > +             __entry->status = status;
> > +     ),
> > +
> > +     TP_printk("%s status=%s", __get_str(name),
> > +             __print_symbolic(__entry->status, RPM_STATUS_STRINGS))
>
> This will be what you want with that last redefine of EM*()
>
> -- Steve
>
>
> > +);
> > +
> >  #endif /* _TRACE_RUNTIME_POWER_H */
> >
> >  /* This part must be outside protection */
>