Re: [PATCH v2 9/9] perf,tracing: Allow function tracing when !RCU

Steven Rostedt
2020-02-14T22:48:49Z

On Fri, 14 Feb 2020 14:38:14 -0600
Kim Phillips <kim.phillips@amd.com> wrote:

> On 2/12/20 3:01 PM, Peter Zijlstra wrote:
> > Since perf is now able to deal with !rcu_is_watching() contexts,
> > remove the restraint.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > ---
> > kernel/trace/trace_event_perf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- a/kernel/trace/trace_event_perf.c
> > +++ b/kernel/trace/trace_event_perf.c
> > @@ -477,7 +477,7 @@ static int perf_ftrace_function_register
> > {
> > struct ftrace_ops *ops = &event->ftrace_ops;
> >
> > - ops->flags = FTRACE_OPS_FL_RCU;
> > + ops->flags = 0;
> > ops->func = perf_ftrace_function_call;
> > ops->private = (void *)(unsigned long)nr_cpu_ids;
>
> If this is the last user of the flag, should all remaining
> FTRACE_OPS_FL_RCU references be removed, too?

Let's wait till Peter's patches goes through a merge cycle or two. I
want to make sure there's no other RCU issues that pop up before we
remove this infrastructure.

-- Steve