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    Subject[PATCH 2/2] perf evsel: Improve error message for uncore events
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    When a group has multiple events and the leader fails it can yield
    errors like:

    $ perf stat -e '{uncore_imc/cas_count_read/},instructions' /bin/true
    Error:
    The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (uncore_imc/cas_count_read/).
    /bin/dmesg | grep -i perf may provide additional information.

    However, when not the group leader <not supported> is given:

    $ perf stat -e '{instructions,uncore_imc/cas_count_read/}' /bin/true
    ...
    1,619,057 instructions
    <not supported> MiB uncore_imc/cas_count_read/

    This is necessary because get_group_fd will fail if the leader fails and
    is the direct result of the check on line 750 of builtin-stat.c in
    stat_handle_error that returns COUNTER_SKIP for the latter case.

    This patch improves the error message to:

    $ perf stat -e '{uncore_imc/cas_count_read/},instructions' /bin/true
    Error:
    Invalid event (uncore_imc/cas_count_read/) in per-thread mode, enable system wide with '-a'.

    Signed-off-by: Ian Rogers <irogers@google.com>
    ---
    tools/perf/util/evsel.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
    index a59fb2ecb84e..48696ff4bddb 100644
    --- a/tools/perf/util/evsel.c
    +++ b/tools/perf/util/evsel.c
    @@ -2950,6 +2950,11 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
    return scnprintf(msg, size, "wrong clockid (%d).", clockid);
    if (perf_missing_features.aux_output)
    return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
    + if ((evsel__leader(evsel) == evsel) &&
    + (evsel->core.leader->nr_members > 1))
    + return scnprintf(msg, size,
    + "Invalid event (%s) in per-thread mode, enable system wide with '-a'.",
    + evsel__name(evsel));
    break;
    case ENODATA:
    return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
    --
    2.34.0.rc2.393.gf8c9666880-goog
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