From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 41FPb85Lt1zF1D8 for ; Tue, 26 Jun 2018 21:54:11 +1000 (AEST) Date: Tue, 26 Jun 2018 19:54:02 +0800 From: Greg Kroah-Hartman To: Pingfan Liu Cc: linux-kernel@vger.kernel.org, Grygorii Strashko , Christoph Hellwig , Bjorn Helgaas , Dave Young , linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCHv2 2/2] drivers/base: reorder consumer and its children behind suppliers Message-ID: <20180626115402.GB30256@kroah.com> References: <1529912859-10475-1-git-send-email-kernelfans@gmail.com> <1529912859-10475-3-git-send-email-kernelfans@gmail.com> <20180625104505.GA3058@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jun 26, 2018 at 11:29:48AM +0800, Pingfan Liu wrote: > On Mon, Jun 25, 2018 at 6:45 PM Greg Kroah-Hartman > wrote: > > > > On Mon, Jun 25, 2018 at 03:47:39PM +0800, Pingfan Liu wrote: > > > commit 52cdbdd49853 ("driver core: correct device's shutdown order") > > > introduces supplier<-consumer order in devices_kset. The commit tries > > > to cleverly maintain both parent<-child and supplier<-consumer order by > > > reordering a device when probing. This method makes things simple and > > > clean, but unfortunately, breaks parent<-child order in some case, > > > which is described in next patch in this series. > > > > There is no "next patch in this series" :( > > > Oh, re-arrange the patches, and forget the comment in log > > > > Here this patch tries to resolve supplier<-consumer by only reordering a > > > device when it has suppliers, and takes care of the following scenario: > > > [consumer, children] [ ... potential ... ] supplier > > > ^ ^ > > > After moving the consumer and its children after the supplier, the > > > potentail section may contain consumers whose supplier is inside > > > children, and this poses the requirement to dry out all consumpers in > > > the section recursively. > > > > > > Cc: Greg Kroah-Hartman > > > 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 > > > --- > > > note: there is lock issue in this patch, should be fixed in next version > > > > Please send patches that you know are correct, why would I want to > > review this if you know it is not correct? > > > > And if the original commit is causing problems for you, why not just > > revert that instead of adding this much-increased complexity? > > > Revert the original commit, then it will expose the error order > "consumer <- supplier" again. > This patch tries to resolve the error and fix the following scenario: > step0: before the consumer device's probing, (note child_a is a > supplier of consumer_a, etc) > [ consumer-X, child_a, ...., child_z] [.... consumer_a, ..., > consumer_z, ....] supplier-X > ^^^ > affected range during moving^^^ > step1: When probing, moving consumer-X after supplier-X > [ child_a, ...., child_z] [.... consumer_a, ..., consumer_z, > ....] supplier-X, consumer-X > But it breaks "parent <-child" seq now, and should be fixed like: > step2: > [.... consumer_a, ..., consumer_z, ....] supplier-X [ > consumer-X, child_a, ...., child_z] <--- > descendants_reorder_after_pos() does it. > Again, the seq "consumer_a <- child_a" breaks the "supplier<-consumer" > order, should be fixed like: > step3: > [.... consumer_z, .....] supplier-X [ consumer-X, child_a, > consumer_a ...., child_z] <--- __device_reorder_consumer() does it. > ^^ affected range^^ > The moving of consumer_a brings us to face the same scenario of step1, > hence we need an external recursion. Something really got messed up here, and this all does not make any sense :( Can you try again? Also, please cc: Rafael on all of this, as he wrote all of this consumer/supplier logic and I am not that familiar with it at all. thanks, greg k-h