Hi Masami,
On Wed, 2018-09-19 at 03:54 +0900, Masami Hiramatsu wrote:
> Hi Tom,
>
> On Mon, 10 Sep 2018 14:10:46 -0500
> Tom Zanussi <zanussi@xxxxxxxxxx> wrote:
>
> > From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
> >
> > Add a 'trace(synthetic_event_name, params)' alternative to
> > synthetic_event_name(params).
> >
> > Currently, the syntax used for generating synthetic events is to
> > invoke synthetic_event_name(params) i.e. use the synthetic event
> > name
> > as a function call.
> >
> > Users requested a new form that more explicitly shows that the
> > synthetic event is in effect being traced. In this version, a new
> > 'trace()' keyword is used, and the synthetic event name is passed
> > in
> > as the first argument.
>
> Hmm, what is the advantage of adding this new form?
>
There's no real advantage other than user preference - Namhyung thought
that since the event-name-as-function-call actions are all defined as
ACTION_TRACE, there should also be an explicit 'trace' action.
So I added it as alternative syntax - the event-name-as-function-call
form remains unchanged.
By the way, I also have a patch implementing your alternative syntax
change, where if you have only one handler, you can do away with the
explicit action.handler form e.g.
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-ts0: \
onmax($wakeup_lat): \
save(next_prio,next_comm,prev_pid,prev_prio,prev_comm):snapshot() \
if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
It just wasn't ready to go in with the v4 patches yet, so I decided
to submit it later as a follow-on.
Tom
> Thanks,
>
