From: Preeti U Murthy Date: Wed, 21 Jan 2015 10:57:25 +0000 (+0530) Subject: sched/idle: Add missing checks to the exit condition of cpu_idle_poll() X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ff6f2d29bd31cdfa1ac494a8b26d2af8ba887d59;p=linux-beck.git sched/idle: Add missing checks to the exit condition of cpu_idle_poll() 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 Reviewed-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Cc: linuxppc-dev@lists.ozlabs.org Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20150121105655.15279.59626.stgit@preeti.in.ibm.com Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index c47fce75e666..aaf1c1d5cf5d 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -47,7 +47,8 @@ static inline int cpu_idle_poll(void) rcu_idle_enter(); trace_cpu_idle_rcuidle(0, smp_processor_id()); local_irq_enable(); - while (!tif_need_resched()) + while (!tif_need_resched() && + (cpu_idle_force_poll || tick_check_broadcast_expired())) cpu_relax(); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); rcu_idle_exit();