[PATCH] perf stat: Fix event grouping on forked task

[Namhyung Kim]

When event group is enabled for forked task (i.e. no target task was
specified) all events were disabled and marked ->enable_on_exec.
However they are not counted at all since only group leader will be
enabled on exec actually. So the result looked like below:

 $ ./perf stat --group -- sleep 1

 Performance counter stats for 'sleep 1':

          0.554926 task-clock                #    0.001 CPUs utilized
     <not counted> context-switches
     <not counted> CPU-migrations
     <not counted> page-faults
     <not counted> cycles
   <not supported> stalled-cycles-frontend
   <not supported> stalled-cycles-backend
     <not counted> instructions
     <not counted> branches
     <not counted> branch-misses

       1.001228093 seconds time elapsed

Fix it by disabling group leader only.

Signed-off-by: Namhyung Kim <namhyung.kim@xxxxxxx>
---
 tools/perf/builtin-stat.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index d14b37ad7638..b2fa61e539c0 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -296,7 +296,8 @@ static int create_perf_stat_counter(struct perf_evsel *evsel,
 	if (system_wide)
 		return perf_evsel__open_per_cpu(evsel, evsel_list->cpus,
 						group, group_fd);
-	if (target_pid == -1 && target_tid == -1) {
+	if (target_pid == -1 && target_tid == -1 &&
+	    (!group || evsel == first)) {
 		attr->disabled = 1;
 		attr->enable_on_exec = 1;
 	}
-- 
1.7.9

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