On Sat, Nov 14, 2020 at 08:07:29AM -0800, Alexei Starovoitov wrote: > On Sat, Nov 14, 2020 at 5:53 AM Florian Lehner <dev@xxxxxxxxxxx> wrote: > > > > At the moment it is not possible to attach a bpf handler to a perf event > > of type PERF_TYPE_SOFTWARE with a configuration of PERF_COUNT_SW_DUMMY. > > It is possible or it is not possible? > > Such "commit log as an abstract statement" patches are a mystery to a reader. > Please explain what problem you're trying to solve and how it's being addressed. Perf events of type software/dummy are just placeholder events and don't require a counting event. So attaching the bpf handler to the overflow_handler of this event does not trigger the execution of the bpf handler. So the idea of this fix was to indicate to the user that attaching a bpf handler to such a perf event is not (yet) supported. > > Signed-off-by: Florian Lehner <dev@xxxxxxxxxxx> > > --- > > kernel/events/core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index da467e1dd49a..4e8846b7ceda 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -9668,6 +9668,10 @@ static int perf_event_set_bpf_handler(struct perf_event *event, u32 prog_fd) > > if (event->prog) > > return -EEXIST; > > > > + if (event->attr.type == PERF_TYPE_SOFTWARE && > > + event->attr.config == PERF_COUNT_SW_DUMMY) > > + return -EOPNOTSUPP; > > Is it a fix or a feature? > If it is a fix please add 'Fixes:' tag. I was not sure how to address it and so I have chosen PATCH. As bpf handlers are still not executed on such events, I also would not call it a feature.
