From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e8.ny.us.ibm.com (e8.ny.us.ibm.com [32.97.182.138]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 041441A0CFA for ; Mon, 19 Jan 2015 16:28:11 +1100 (AEDT) Received: from /spool/local by e8.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 19 Jan 2015 00:28:09 -0500 Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id DA9186E8047 for ; Mon, 19 Jan 2015 00:19:59 -0500 (EST) Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t0J5S73026149068 for ; Mon, 19 Jan 2015 05:28:07 GMT Received: from d01av01.pok.ibm.com (localhost [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t0J5S6X1001224 for ; Mon, 19 Jan 2015 00:28:06 -0500 Subject: [PATCH] idle/tick-broadcast: Exit cpu idle poll loop when cleared from tick_broadcast_force_mask From: Preeti U Murthy To: tglx@linutronix.de Date: Mon, 19 Jan 2015 10:57:54 +0530 Message-ID: <20150119052754.20256.54721.stgit@preeti.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Cc: peterz@infradead.org, linuxppc-dev@lists.ozlabs.org, mingo@kernel.org, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , An idle cpu enters cpu_idle_poll() if it is set in the tick_broadcast_force_mask. This is so that it does not incur the overhead of entering idle states when it is expected to be woken up anytime then through a broadcast IPI. The condition that forces an exit out of the idle polling is the check on setting of the TIF_NEED_RESCHED flag for the idle thread. When the broadcast IPI does arrive, it is not guarenteed that the handler sets the TIF_NEED_RESCHED flag. Hence although the cpu is cleared in the tick_broadcast_force_mask, it continues to loop in cpu_idle_poll unnecessarily wasting power. Hence exit the idle poll loop if the tick_broadcast_force_mask gets cleared and enter idle states. Of course if the cpu has entered cpu_idle_poll() on being asked to poll explicitly, it continues to poll till it is asked to reschedule. Signed-off-by: Preeti U Murthy --- 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) 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();