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    Subject[PATCH 04/10] perf python: Fix pyrf_evlist__read_on_cpu event consuming
    Date
    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.

    Link: http://lkml.kernel.org/n/tip-8dbalvrufeisa4cioyd9k65i@git.kernel.org
    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    ---
    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 d0c1267741ee..c68ef0319114 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);
    --
    2.4.11
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