From mboxrd@z Thu Jan 1 00:00:00 1970 From: joeyli Subject: Re: A udev rule to serve the change event of ACPI container? Date: Thu, 3 Aug 2017 17:52:57 +0800 Message-ID: <20170803095257.GD5730@linux-l9pv.suse> References: <20170714144414.GM2901@linux-l9pv.suse> <20170717090525.GF12888@dhcp22.suse.cz> <20170719090910.GK26098@linux-l9pv.suse> <20170724085702.GE25221@dhcp22.suse.cz> <20170724092921.GF3034@linux-l9pv.suse> <20170725124837.GH26723@dhcp22.suse.cz> <20170731073845.GC2946@linux-l9pv.suse> <20170802090143.GG2524@dhcp22.suse.cz> <20170803092237.GC5730@linux-l9pv.suse> <20170803093153.GG12521@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from smtp.nue.novell.com ([195.135.221.5]:48644 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751775AbdHCJxI (ORCPT ); Thu, 3 Aug 2017 05:53:08 -0400 Content-Disposition: inline In-Reply-To: <20170803093153.GG12521@dhcp22.suse.cz> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Michal Hocko Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Yasuaki Ishimatsu On Thu, Aug 03, 2017 at 11:31:53AM +0200, Michal Hocko wrote: > On Thu 03-08-17 17:22:37, Joey Lee wrote: > > On Wed, Aug 02, 2017 at 11:01:43AM +0200, Michal Hocko wrote: > > > On Mon 31-07-17 15:38:45, Joey Lee wrote: > [...] > > > > So, the behavior is: > > > > > > > > Kernel received ejection event, set _Eject_ flag on container object > > > > -> Kernel sends offline events to all children devices > > > > -> User space performs cleaning jobs and offlines each child device > > > > -> Kernel detects all children offlined > > > > -> Kernel removes objects and calls power off(_EJ0) > > > > > > Yes this is what I've had in mind. It is the "kernel detects..." part > > > which is not implemented now and that requires us to do the explicit > > > eject from userspace, correct? > > > > > > > Yes, the _Eject_ flag and _detects_ part are not implemented now. > > > > In this approach, kernel still relies on user space to trigger the > > offline. The ejection process is still not transparent to user space. > > Is it what you want? > > But as long as there is no auto-offlining then there is no other choice > no? Besides that userspace even shouldn't care about the fact that the If Yasuaki's problem is already fixed in mainline, then the auto-offlining will be possible. > eject is in progress. That is a BIOS->OS deal AFAIU. All the userspace > cares about is the proper cleanup of the resources and that happens at > the offline time. > I agree! User space doesn't need to know the detail of kobject cleaning and ejection stages. > > > > If anyone onlined one of the children devices in the term of waiting > > > > userland offlines all children, then the _Eject_ flag will be clean > > > > and ejection process will be interrupted. In this situation, administrator > > > > needs to trigger ejection event again. > > > > > > yes > > > > > > > Do you think that the race hurts anything? > > > > > > What kind of race? > > > > User space set a child online before all childreen offlined, then > > the _Eject_ flag is cleaned and the ejection process is interrupted. > > Is this really a race though? Kernel will always have a full picture and > if userspace wants to online some part then the eject cannot succeed. > This is something that a userspace driver eject cannot possibly handle. Then I agree. I am waiting Yasuaki's response and want to know Rafael's and Yasuaki's opinions about the _Eject_ flag approach. Thanks a lot! Joey Lee