perf_event: Clean up perf_event_init_task()

While at it: we can traverse ctx->group_list to get all
group leader, it should be safe since we hold ctx->mutex.

Changlog v1->v2:

  - remove WARN_ON_ONCE() according to Peter Zijlstra's suggestion

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <4ABC5AF9.6060808@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 3 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index e50543db642a..e491fb087939 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4767,9 +4767,7 @@ int perf_event_init_task(struct task_struct *child)
          * We dont have to disable NMIs - we are only looking at
          * the list, not manipulating it:
          */
-        list_for_each_entry_rcu(event, &parent_ctx->event_list, event_entry) {
-                if (event != event->group_leader)
-                        continue;
+        list_for_each_entry(event, &parent_ctx->group_list, group_entry) {
 
                 if (!event->attr.inherit) {
                         inherited_all = 0;