[tip:perf/core] perf: Do not get values from disabled counters in group format read

[tip-bot for Jiri Olsa <tipbot@zytor.com>]

Commit-ID:  6f5ab0019fd328b50a8488c9e5193fc1dbd8d6ed
Gitweb:     http://git.kernel.org/tip/6f5ab0019fd328b50a8488c9e5193fc1dbd8d6ed
Author:     Jiri Olsa <jolsa@redhat.com>
AuthorDate: Mon, 15 Oct 2012 20:13:45 +0200
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 7 Aug 2013 17:35:19 -0300

perf: Do not get values from disabled counters in group format read

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>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-wwkjb0bbcuslnz0klrmqi26r@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 kernel/events/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5200b60..e82e700 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4388,7 +4388,8 @@ static void perf_output_read_group(struct perf_output_handle *handle,
 	list_for_each_entry(sub, &leader->sibling_list, group_entry) {
 		n = 0;
 
-		if (sub != event)
+		if ((sub != event) &&
+		    (sub->state == PERF_EVENT_STATE_ACTIVE))
 			sub->pmu->read(sub);
 
 		values[n++] = perf_event_count(sub);