perf: Round robin flexible groups of events using list_rotate_left()

This is more proper that doing it through a list_for_each_entry()
that breaks after the first entry.

v2: Don't rotate pinned groups as its not needed to time share
them.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>

1 files changed, 4 insertions, 13 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c9f8a757649..bbebe283263 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1454,25 +1454,16 @@ static void perf_ctx_adjust_freq(struct perf_event_context *ctx)
  */
 static void rotate_ctx(struct perf_event_context *ctx)
 {
-        struct perf_event *event;
-
         if (!ctx->nr_events)
                 return;
 
         raw_spin_lock(&ctx->lock);
-        /*
-         * Rotate the first entry last (works just fine for group events too):
-         */
+
+        /* Rotate the first entry last of non-pinned groups */
         perf_disable();
-        list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
-                list_move_tail(&event->group_entry, &ctx->pinned_groups);
-                break;
-        }
 
-        list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
-                list_move_tail(&event->group_entry, &ctx->flexible_groups);
-                break;
-        }
+        list_rotate_left(&ctx->flexible_groups);
+
         perf_enable();
 
         raw_spin_unlock(&ctx->lock);