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Subject[tip:perf/core] perf python: Fix pyrf_evlist__read_on_cpu event consuming
Commit-ID:  e8968e654191390a1300f0847250353a1c9da30d
Gitweb: http://git.kernel.org/tip/e8968e654191390a1300f0847250353a1c9da30d
Author: Jiri Olsa <jolsa@kernel.org>
AuthorDate: Sun, 10 Jul 2016 13:07:56 +0200
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 12 Jul 2016 16:16:44 -0300

perf python: Fix pyrf_evlist__read_on_cpu event consuming

We can't consume the event before parsing it. Under heavy load we could
get caught by kernel writer overwriting the event we're trying to parse.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1468148882-10362-5-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/python.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index d0c1267..c68ef03 100644
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -865,12 +865,14 @@ static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist,
PyObject *pyevent = pyrf_event__new(event);
struct pyrf_event *pevent = (struct pyrf_event *)pyevent;

- perf_evlist__mmap_consume(evlist, cpu);
-
if (pyevent == NULL)
return PyErr_NoMemory();

err = perf_evlist__parse_sample(evlist, event, &pevent->sample);
+
+ /* Consume the even only after we parsed it out. */
+ perf_evlist__mmap_consume(evlist, cpu);
+
if (err)
return PyErr_Format(PyExc_OSError,
"perf: can't parse sample, err=%d", err);
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