From patchwork Wed Mar 14 14:08:57 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 10282237 X-Patchwork-Delegate: rjw@sisk.pl Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 594BD60211 for ; Wed, 14 Mar 2018 14:08:37 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4941F28968 for ; Wed, 14 Mar 2018 14:08:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3D33E2896E; Wed, 14 Mar 2018 14:08:37 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3D89B28968 for ; Wed, 14 Mar 2018 14:08:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751408AbeCNOIZ (ORCPT ); Wed, 14 Mar 2018 10:08:25 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:50625 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751366AbeCNOIY (ORCPT ); Wed, 14 Mar 2018 10:08:24 -0400 Received: from 79.184.254.228.ipv4.supernova.orange.pl (79.184.254.228) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83) id e8fc3f4d14658717; Wed, 14 Mar 2018 15:08:22 +0100 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 v3] cpuidle: poll_state: Add time limit to poll_idle() Date: Wed, 14 Mar 2018 15:08:57 +0100 Message-ID: <3111105.SmgpqUHPkp@aspire.rjw.lan> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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(). Suggested-by: Peter Zijlstra Signed-off-by: Rafael J. Wysocki --- v2 -> v3: Use local_clock() for time measurements and drop the counter, since that should be lightweight enough (as suggested by Peter). --- drivers/cpuidle/poll_state.c | 11 ++++++++++- 1 file changed, 10 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 @@ -6,15 +6,24 @@ #include #include +#include #include +#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16) + static int __cpuidle poll_idle(struct cpuidle_device *dev, struct cpuidle_driver *drv, int index) { + u64 time_start = local_clock(); + local_irq_enable(); if (!current_set_polling_and_test()) { - while (!need_resched()) + while (!need_resched()) { cpu_relax(); + + if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT) + break; + } } current_clr_polling();