[PATCH 02/11] perf: Do not get values from disabled counters in group format read

[Jiri Olsa <jolsa@redhat.com>]

It's possible some of the counters in the group could be
disabled when sampling member of the event group is reading
the rest via PERF_SAMPLE_READ sample type processing. Disabled
counters could then produce wrong numbers.

Fixing that by reading only enabled counters for PERF_SAMPLE_READ
sample type processing.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
---
 kernel/events/core.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 32aec40..5220d01 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4012,12 +4012,24 @@ static void perf_output_read_group(struct perf_output_handle *handle,
 	__output_copy(handle, values, n * sizeof(u64));
 
 	list_for_each_entry(sub, &leader->sibling_list, group_entry) {
+		u64 value = 0;
 		n = 0;
 
-		if (sub != event)
-			sub->pmu->read(sub);
+		/*
+		 * We are NOT interested in disabled counters,
+		 * giving us strange values and keeping us from
+		 * good night sleep!!!
+		 */
+		if (sub->state > PERF_EVENT_STATE_OFF) {
+
+			if (sub != event)
+				sub->pmu->read(sub);
+
+			value = perf_event_count(sub);
+		}
+
+		values[n++] = value;
 
-		values[n++] = perf_event_count(sub);
 		if (read_format & PERF_FORMAT_ID)
 			values[n++] = primary_event_id(sub);
 
-- 
1.7.11.4