From 026249ef100b5384b6c74c360db46728e98354da Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Sat, 20 Apr 2013 15:58:34 +0200
Subject: 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 <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
---
 kernel/events/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'kernel/events')

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 75b58bb..ddb993b 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);
-- 
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