From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753816AbbGFQGN (ORCPT ); Mon, 6 Jul 2015 12:06:13 -0400 Received: from www.linutronix.de ([62.245.132.108]:56048 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752670AbbGFQGK (ORCPT ); Mon, 6 Jul 2015 12:06:10 -0400 Date: Mon, 6 Jul 2015 18:06:03 +0200 (CEST) From: Thomas Gleixner To: Sudeep Holla cc: LKML , Ingo Molnar , Peter Zijlstra , Preeti U Murthy , Suzuki Poulose , Lorenzo Pieralisi , Catalin Marinas , "Rafael J. Wysocki" Subject: Re: [patch 1/2] tick/broadcast: Prevent deep idle states if no broadcast device available In-Reply-To: <559AA256.5040305@arm.com> Message-ID: References: <20150705205032.103910828@linutronix.de> <20150705205221.724282507@linutronix.de> <559A9A2B.2030705@arm.com> <559AA256.5040305@arm.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 6 Jul 2015, Sudeep Holla wrote: > On 06/07/15 16:35, Thomas Gleixner wrote: > > Well, we should figure out what happens while we are at it before > > everything gets paged out again. > > > > True. I just wanted to mention that this patch works for all the > practical purposes. > > > In the case of CONFIG_NOHZ=n and CONFIG_HIGHRES=n the broadcast > > hrtimer is not compiled as it depends on CONFIG_TICK_ONESHOT, so it > > works via the bc.evtdev == NULL check. > > > > With either option enabled CONFIG_TICK_ONESHOT gets set, so the > > broadcast timer gets installed but somehow does not work proper if > > nohz and highres are disabled on the kernel command line. > > > > Let me know if you want to test something to help debug this configuration. Can you try the following delta patch? Thanks, tglx --- Index: tip/kernel/time/tick-broadcast.c =================================================================== --- tip.orig/kernel/time/tick-broadcast.c +++ tip/kernel/time/tick-broadcast.c @@ -360,14 +360,15 @@ void tick_broadcast_control(enum tick_br cpumask_set_cpu(cpu, tick_broadcast_on); if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) { /* - * Only shutdown the cpu local device, if the - * broadcast device exists and is in periodic - * mode. The latter check prevents a hickup - * during the switch from periodic to oneshot - * mode. + * Only shutdown the cpu local device, if: + * + * - the broadcast device exists + * - the broadcast device is not a hrtimer based one + * - the broadcast device is in periodic mode to + * avoid a hickup during switch to oneshot mode */ - if (bc != NULL && tick_broadcast_device.mode == - TICKDEV_MODE_PERIODIC) + if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) && + tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) clockevents_shutdown(dev); } break; @@ -697,14 +698,18 @@ int __tick_broadcast_oneshot_control(enu * shutdown. */ ret = broadcast_needs_cpu(bc, cpu); + if (ret) + goto out; /* - * If the hrtimer broadcast check tells us that the - * cpu cannot go deep idle, or if the broadcast device - * is in periodic mode, we just return. + * If the broadcast device is in periodic mode, we + * return. */ - if (ret || tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) - goto out; + if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) { + /* If it is a hrtimer based broadcast, return busy */ + if (bc->features & CLOCK_EVT_FEAT_HRTIMER) + ret = -EBUSY; + } if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) { WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));