From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Wagner Subject: Re: [RFC v0 2/9] suspend: Add getter function to report if freezing is active Date: Tue, 8 Sep 2015 10:19:35 +0200 Message-ID: <55EE9A17.4010601@bmw-carit.de> References: <1441373702-31796-1-git-send-email-daniel.wagner@bmw-carit.de> <1683655.HLd9k04Slu@vostro.rjw.lan> <55ED510F.7090702@bmw-carit.de> <1597290.WZUafm8kGW@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mail.bmw-carit.de ([62.245.222.98]:51348 "EHLO mail.bmw-carit.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753308AbbIHITm (ORCPT ); Tue, 8 Sep 2015 04:19:42 -0400 In-Reply-To: <1597290.WZUafm8kGW@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: linux-kernel@vger.kernel.org, Len Brown , Pavel Machek , linux-pm@vger.kernel.org On 09/07/2015 11:44 PM, Rafael J. Wysocki wrote: > On Monday, September 07, 2015 10:55:43 AM Daniel Wagner wrote: >> On 09/05/2015 04:11 AM, Rafael J. Wysocki wrote: >>> On Friday, September 04, 2015 03:34:55 PM Daniel Wagner wrote: >>>> Instead encode the FREEZE state via the CPU state we allow the >>>> interesting subsystems (MCE, microcode) to query the power >>>> subsystem directly. >>> >>> A use case, please. >> >> The motivation for this change is to reduce the complexity in the >> hotplug code. As tried to point out in the cover letter, the FROZEN >> bits have only a bunch of users after all those years (2007). So it is >> worth to have all the notifier users to handle the FROZEN state? >> >> Don't know if that counts as use case. > > Well, the code you're changing has nothing to do with CPU hotplug and > CPU_TASKS_FROZEN. It is about suspend-to-idle. > > Please grep for suspend_freeze_state and see what it is used for. > > There is some confusion in the naming, but that is about the freezing of > the whole system, while CPU_TASKS_FROZEN is about the freezing of user space. You are right. I got confused by all those frozen/freezing naming scheme. >>>> Most notifiers are not interested at all >>>> in this information so rather have explicit calls to freeze_active() >>>> instead adding complexity to the rest of the users of the CPU >>>> notifiers. >>> >>> Why does it has anything to do with CPU notifiers? >> >> cpu_{down|up} will call the notifiers with the CPU_TASK_FROZEN bit set >> and so most notifiers are doing >> >> switch (actcion ~CPU_TASK_FROZEN) >> >> to filter it out because they don't need to handle the system wide >> ongoing freeze operations. >> >>> We don't offline CPUs for suspend-to-idle. >> >> Sure. As I said the motivation is to reduce the complexity in the >> hotplug code. > > You need to fine a different way to do that. I'll try something else. Thanks for taking the time explaining! cheers, Daniel