From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41LH576nTlzF0ZD for ; Wed, 4 Jul 2018 20:18:34 +1000 (AEST) From: "Rafael J. Wysocki" To: Pingfan Liu Cc: Grygorii Strashko , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Christoph Hellwig , Bjorn Helgaas , Dave Young , linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Linux PM Subject: Re: [PATCHv3 3/4] drivers/base: clean up the usage of devices_kset_move_last() Date: Wed, 04 Jul 2018 12:17:06 +0200 Message-ID: <2842715.a5PfnD4e6X@aspire.rjw.lan> In-Reply-To: References: <1530600642-25090-1-git-send-email-kernelfans@gmail.com> <3375966.ydPZj5TMVj@aspire.rjw.lan> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wednesday, July 4, 2018 6:40:09 AM CEST Pingfan Liu wrote: > On Tue, Jul 3, 2018 at 10:28 PM Rafael J. Wysocki wrote: > > > > On Tuesday, July 3, 2018 8:50:41 AM CEST Pingfan Liu wrote: > > > Clean up the referring to the code in commit 52cdbdd49853 ("driver core: > > > correct device's shutdown order"). So later we can revert it safely. > > > > > > Cc: Greg Kroah-Hartman > > > Cc: Rafael J. Wysocki > > > Cc: Grygorii Strashko > > > Cc: Christoph Hellwig > > > Cc: Bjorn Helgaas > > > Cc: Dave Young > > > Cc: linux-pci@vger.kernel.org > > > Cc: linuxppc-dev@lists.ozlabs.org > > > Signed-off-by: Pingfan Liu > > > --- > > > drivers/base/core.c | 7 ------- > > > 1 file changed, 7 deletions(-) > > > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > > index 684b994..db3deb8 100644 > > > --- a/drivers/base/core.c > > > +++ b/drivers/base/core.c > > > @@ -127,13 +127,6 @@ static int device_reorder_to_tail(struct device *dev, void *not_used) > > > { > > > struct device_link *link; > > > > > > - /* > > > - * Devices that have not been registered yet will be put to the ends > > > - * of the lists during the registration, so skip them here. > > > - */ > > > - if (device_is_registered(dev)) > > > - devices_kset_move_last(dev); > > > - > > > if (device_pm_initialized(dev)) > > > device_pm_move_last(dev); > > > > You can't do this. > > > > If you do it, that will break power management in some situations. > > > Could you shed light on it? I had a quick browsing of pm code, but it > is a big function, and I got lost in it. > If the above code causes failure, then does it imply that the seq in > devices_kset should be the same as dpm_list? Generally, yes it should. > But in device_shutdown(), it only intersect with pm by > pm_runtime_get_noresume(dev) and pm_runtime_barrier(dev). How do these > function affect the seq in dpm_list? They are not related to dpm_list directly. However, if you shut down a supplier device before its consumer and that involves power management, then the consumer shutdown may fail and lock up the system I asked you elsewhere to clearly describe the problem you are trying to address. Please do that in the first place. Thanks, Rafael