Re: [PATCH] perf/core: Fix perf_sample_data not properly initialized for different swevents in perf_tp_event()

[Yang Jihong]

Hello,

On 2023/4/18 18:25, Peter Zijlstra wrote:
> On Tue, Apr 18, 2023 at 09:35:23AM +0800, Yang Jihong wrote:
>
> > > I'm thinking perhaps those flags that update ->dyn_size are the problem?
> > > At the same time, Should you not also then clear dyn_size?
>
> > Yes, according to the code, dyn_size should also be cleared.
> > Maybe we need to change it to the following, which would be more
> > appropriate?
> >
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -10144,14 +10144,14 @@ void perf_tp_event(u16 event_type, u64 count, void
> > *record, int entry_size,
> >                  },
> >          };
> >
> > -       perf_sample_data_init(&data, 0, 0);
> > -       perf_sample_save_raw_data(&data, &raw);
> > -
> >          perf_trace_buf_update(record, event_type);
> >
> >          hlist_for_each_entry_rcu(event, head, hlist_entry) {
> > -               if (perf_tp_event_match(event, &data, regs))
> > +               if (perf_tp_event_match(event, &data, regs)) {
> > +                       perf_sample_data_init(&data, 0, 0);
> > +                       perf_sample_save_raw_data(&data, &raw);
> >                          perf_swevent_event(event, count, &data, regs);
> > +               }
> >          }
>
> That is certainly the safe option. I just went through the list and
> while there's certainly a number of options we'll recompute for naught,
> most of them are indeed either dyn_size or event specific :/
>
> So yeah, please send the above as v2.
OK, will send v2 according to above fix solution.

Thanks,
Yang.