[PATCH V2] cpuidle: Add missing checks to the exit condition of cpu_idle_poll()

Preeti U Murthy preeti at linux.vnet.ibm.com
Wed Jan 21 21:57:25 AEDT 2015

cpu_idle_poll() is entered into when either the cpu_idle_force_poll is set or
tick_check_broadcast_expired() returns true. The exit condition from
cpu_idle_poll() is tif_need_resched().

However this does not take into account scenarios where cpu_idle_force_poll
changes or tick_check_broadcast_expired() returns false, without setting
the resched flag. So a cpu will be caught in cpu_idle_poll() needlessly,
thereby wasting power. Add an explicit check on cpu_idle_force_poll and
tick_check_broadcast_expired() to the exit condition of cpu_idle_poll()
to avoid this.

Signed-off-by: Preeti U Murthy <preeti at linux.vnet.ibm.com>
Changes from V1: Modified the Changelog

 kernel/sched/idle.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index c47fce7..aaf1c1d 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -47,7 +47,8 @@ static inline int cpu_idle_poll(void)
 	trace_cpu_idle_rcuidle(0, smp_processor_id());
-	while (!tif_need_resched())
+	while (!tif_need_resched() &&
+		(cpu_idle_force_poll || tick_check_broadcast_expired()))
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());

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