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    Subject[PATCH 4.9 162/241] perf stat: Fix bug in handling events in error state
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Stephane Eranian <eranian@google.com>


    [ Upstream commit db49a71798a38f3ddf3f3462703328dca39b1ac7 ]

    (This is a patch has been sitting in the Intel CQM/CMT driver series for
    a while, despite not depend on it. Sending it now independently since
    the series is being discarded.)

    When an event is in error state, read() returns 0 instead of sizeof()
    buffer. In certain modes, such as interval printing, ignoring the 0
    return value may cause bogus count deltas to be computed and thus
    invalid results printed.

    This patch fixes this problem by modifying read_counters() to mark the
    event as not scaled (scaled = -1) to force the printout routine to show
    <NOT COUNTED>.

    Signed-off-by: Stephane Eranian <eranian@google.com>
    Reviewed-by: David Carrillo-Cisneros <davidcc@google.com>
    Acked-by: Jiri Olsa <jolsa@redhat.com>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Cc: Paul Turner <pjt@google.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Wang Nan <wangnan0@huawei.com>
    Link: http://lkml.kernel.org/r/20170412182301.44406-1-davidcc@google.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    tools/perf/builtin-stat.c | 12 +++++++++---
    tools/perf/util/evsel.c | 4 ++--
    2 files changed, 11 insertions(+), 5 deletions(-)

    --- a/tools/perf/builtin-stat.c
    +++ b/tools/perf/builtin-stat.c
    @@ -311,8 +311,12 @@ static int read_counter(struct perf_evse
    struct perf_counts_values *count;

    count = perf_counts(counter->counts, cpu, thread);
    - if (perf_evsel__read(counter, cpu, thread, count))
    + if (perf_evsel__read(counter, cpu, thread, count)) {
    + counter->counts->scaled = -1;
    + perf_counts(counter->counts, cpu, thread)->ena = 0;
    + perf_counts(counter->counts, cpu, thread)->run = 0;
    return -1;
    + }

    if (STAT_RECORD) {
    if (perf_evsel__write_stat_event(counter, cpu, thread, count)) {
    @@ -337,12 +341,14 @@ static int read_counter(struct perf_evse
    static void read_counters(void)
    {
    struct perf_evsel *counter;
    + int ret;

    evlist__for_each_entry(evsel_list, counter) {
    - if (read_counter(counter))
    + ret = read_counter(counter);
    + if (ret)
    pr_debug("failed to read counter %s\n", counter->name);

    - if (perf_stat_process_counter(&stat_config, counter))
    + if (ret == 0 && perf_stat_process_counter(&stat_config, counter))
    pr_warning("failed to process counter %s\n", counter->name);
    }
    }
    --- a/tools/perf/util/evsel.c
    +++ b/tools/perf/util/evsel.c
    @@ -1221,7 +1221,7 @@ int perf_evsel__read(struct perf_evsel *
    if (FD(evsel, cpu, thread) < 0)
    return -EINVAL;

    - if (readn(FD(evsel, cpu, thread), count, sizeof(*count)) < 0)
    + if (readn(FD(evsel, cpu, thread), count, sizeof(*count)) <= 0)
    return -errno;

    return 0;
    @@ -1239,7 +1239,7 @@ int __perf_evsel__read_on_cpu(struct per
    if (evsel->counts == NULL && perf_evsel__alloc_counts(evsel, cpu + 1, thread + 1) < 0)
    return -ENOMEM;

    - if (readn(FD(evsel, cpu, thread), &count, nv * sizeof(u64)) < 0)
    + if (readn(FD(evsel, cpu, thread), &count, nv * sizeof(u64)) <= 0)
    return -errno;

    perf_evsel__compute_deltas(evsel, cpu, thread, &count);

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