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SubjectRe: [PATCH 1/5] perf top: Use active evsel for non-sample events on old kernel
Em Sun, Jan 29, 2012 at 05:55:52PM +0900, Namhyung Kim escreveu:
> If multiple events are specified on old kernel,
> perf_evlist__id2evsel() returns NULL for non-sampling events
> since the sample.id doesn't contain valid value, and it triggers
> assert below. If only one event is given, the function returns
> the evsel regardless of sample.id, this is why most case cause
> no problem on old kernel.
>
> Fix it by using active evsel.

How about this one instead:

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index a6d50e3..3ffb320 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -349,6 +349,10 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
hlist_for_each_entry(sid, pos, head, node)
if (sid->id == id)
return sid->evsel;
+
+ if (!perf_evlist__sample_id_all(evlist))
+ return list_entry(evlist->entries.next, struct perf_evsel, node);
+
return NULL;
}

That way we won't have to patch other tools that would get the same
problem in such new tool/old kernel combos, right?
Do you see any problem with not checking the header type?

Also please try to avoid using perf_session fields, prefer to use
perf_{evlist,evsel} when possible, in this case you could use
perf_evlist__sample_id_all(evlist), for instance.
- Arnaldo

> Signed-off-by: Namhyung Kim <namhyung@gmail.com>
> ---
> tools/perf/builtin-top.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index e8b033c074f9..f68fba52c8d8 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -771,6 +771,14 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
> }
>
> evsel = perf_evlist__id2evsel(session->evlist, sample.id);
> + if (evsel == NULL && !session->sample_id_all &&
> + event->header.type != PERF_RECORD_SAMPLE) {
> + /*
> + * Old kernel, no sample_id_all field.
> + * Just use active evsel.
> + */
> + evsel = top->sym_evsel;
> + }
> assert(evsel != NULL);
>
> origin = event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
> --
> 1.7.8.2


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