perf: New helper to prevent full dynticks CPUs from stopping tick

Provide a new helper that help full dynticks CPUs to prevent
from stopping their tick in case there are events in the local
rotation list.

This way we make sure that perf_event_task_tick() is serviced
on demand.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Geoff Levand <[email protected]>
Cc: Gilad Ben Yossef <[email protected]>
Cc: Hakan Akkan <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kevin Hilman <[email protected]>
Cc: Li Zhong <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Jiri Olsa <[email protected]>

1 files changed, 10 insertions, 0 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 75b58bb75b32..ddb993b52190 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2560,6 +2560,16 @@ done:
 		list_del_init(&cpuctx->rotation_list);
 }
 
+#ifdef CONFIG_NO_HZ_FULL
+bool perf_event_can_stop_tick(void)
+{
+	if (list_empty(&__get_cpu_var(rotation_list)))
+		return true;
+	else
+		return false;
+}
+#endif
+
 void perf_event_task_tick(void)
 {
 	struct list_head *head = &__get_cpu_var(rotation_list);