From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932163AbeCKKPN (ORCPT ); Sun, 11 Mar 2018 06:15:13 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:41952 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932116AbeCKKPM (ORCPT ); Sun, 11 Mar 2018 06:15:12 -0400 From: "Rafael J. Wysocki" To: Linux PM Cc: Peter Zijlstra , Frederic Weisbecker , Thomas Gleixner , Paul McKenney , Thomas Ilsche , Doug Smythies , Rik van Riel , Aubrey Li , Mike Galbraith , LKML Subject: [PATCH] cpuidle: poll_state: Add time limit to poll_idle() Date: Sun, 11 Mar 2018 11:15:49 +0100 Message-ID: <6734090.QOs8nIFVJO@aspire.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rafael J. Wysocki If poll_idle() is allowed to spin until need_resched() returns 'true', it may actually spin for a much longer time than expected by the idle governor, since set_tsk_need_resched() is not always called by the timer interrupt handler. If that happens, the CPU may spend much more time than anticipated in the "polling" state. To prevent that from happening, limit the time of the spinning loop in poll_idle(). Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/poll_state.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) Index: linux-pm/drivers/cpuidle/poll_state.c =================================================================== --- linux-pm.orig/drivers/cpuidle/poll_state.c +++ linux-pm/drivers/cpuidle/poll_state.c @@ -5,16 +5,31 @@ */ #include +#include #include #include +#define POLL_IDLE_TIME_CHECK_COUNT 10000 +#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16) + static int __cpuidle poll_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + ktime_t start = ktime_get(); + local_irq_enable(); if (!current_set_polling_and_test()) { - while (!need_resched()) + unsigned int time_check_counter = 0; + + while (!need_resched()) { cpu_relax(); + if (time_check_counter++ < POLL_IDLE_TIME_CHECK_COUNT) + continue; + + time_check_counter = 0; + if (ktime_sub(ktime_get(), start) > POLL_IDLE_TIME_LIMIT) + break; + } } current_clr_polling();