Re: [PATCH v3 01/17] tools/rv: Do not skip idle in trace

[Gabriele Monaco <gmonaco@redhat.com>]

On Wed, 2025-07-16 at 13:50 +0200, Peter Zijlstra wrote:
> On Tue, Jul 15, 2025 at 09:14:18AM +0200, Gabriele Monaco wrote:
> > Currently, the userspace RV tool skips trace events triggered by
> > the RV
> > tool itself, this can be changed by passing the parameter -s, which
> > sets
> > the variable config_my_pid to 0 (instead of the tool's PID).
> > The current condition for per-task monitors (config_has_id) does
> > not
> > check that config_my_pid isn't 0 to skip. In case we pass -s, we
> > show
> > events triggered by RV but don't show those triggered by idle (PID
> > 0).
> > 
> > Fix the condition to account this scenario.
> 
> The distinction between !my_pid and has_id is that you can in fact
> trace
> pid-0 if you want?
> 

Yes pretty much, no flag is meant to skip events from pid-0.


has_id is used to distinguish between per-cpu/global monitors (they
don't have id) and per-task monitors (the id is the pid).

The case with !has_id is correctly checking for both my_pid != 0 while
skipping events associated to my_pid (rv thread's PID).

In the other case we end up with:
* -s skipping events generated by the tool (correct)
* omitting -s skips events generated by pid-0 (undesired)


> > Fixes: 6d60f89691fc ("tools/rv: Add in-kernel monitor interface")
> > Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
> > ---
> >  tools/verification/rv/src/in_kernel.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/verification/rv/src/in_kernel.c
> > b/tools/verification/rv/src/in_kernel.c
> > index c0dcee795c0de..72b03bae021cd 100644
> > --- a/tools/verification/rv/src/in_kernel.c
> > +++ b/tools/verification/rv/src/in_kernel.c
> > @@ -429,7 +429,7 @@ ikm_event_handler(struct trace_seq *s, struct
> > tep_record *record,
> >  
> >  	tep_get_common_field_val(s, trace_event, "common_pid",
> > record, &pid, 1);
> >  
> > -	if (config_has_id && (config_my_pid == id))
> > +	if (config_my_pid && config_has_id && (config_my_pid ==
> > id))
> >  		return 0;
> >  	else if (config_my_pid && (config_my_pid == pid))
> >  		return 0;
> > -- 
> > 2.50.1
> >