[PATCH v3 45/46] perf/stat: fix bug in handling events in error state

[David Carrillo-Cisneros]

From: Stephane Eranian <eran...@google.com>

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 <eran...@google.com>
---
 tools/perf/builtin-stat.c | 12 +++++++++---
 tools/perf/util/evsel.c   |  4 ++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 688dea7..c3c4b49 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -310,8 +310,12 @@ static int read_counter(struct perf_evsel *counter)
                        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)) {
@@ -336,12 +340,14 @@ static int read_counter(struct perf_evsel *counter)
 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);
        }
 }
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 8bc2711..d54efb5 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1221,7 +1221,7 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu, 
int thread,
        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 perf_evsel *evsel,
        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);
-- 
2.8.0.rc3.226.g39d4020