From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66056C433E0 for ; Thu, 4 Feb 2021 22:24:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16BD764FAD for ; Thu, 4 Feb 2021 22:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229613AbhBDWYw (ORCPT ); Thu, 4 Feb 2021 17:24:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:33222 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229534AbhBDWYv (ORCPT ); Thu, 4 Feb 2021 17:24:51 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A10F664FAA; Thu, 4 Feb 2021 22:24:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612477449; bh=JutpsfoRnwZiwX9WSRX+9vPCxj9lG7YuiARSCN/pfb8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=R4EZehMHVo5fn0vaQZAo7gB2GbIMgL9Qiush/t7IxMNPcsOg65YtqQLWvt4bMJG5r 9lA0cGGOXqj2x+6Sp6C+nsCP9UpoVG7H2Kxadl5eCcGEWjM0L1VWnTD+yhLy8bbnsj U4aqcqXxREXCmyDZNMlany8b0SXougiBRi6sN4iQGcB5bfs1R3oWkHK+yVzaMfmSXq rZsWXNB+48T84kW+wWsLjJRqtCcgMiozGaAzlgcOvMHWIqJm9nQDeLygHVBngpqhMd m0VgANBrq/FqFnSDuQpzpaQ4th8XfYs1SbCzwN0SE6+YWLxM1aHUhPjKLibKF95OFJ oFe7uv9RQ7SFw== Received: by pali.im (Postfix) id 42B99736; Thu, 4 Feb 2021 23:24:07 +0100 (CET) Date: Thu, 4 Feb 2021 23:24:07 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Bjorn Helgaas Cc: Daniel Vetter , LKML , Stephen Rothwell , linux-samsung-soc@vger.kernel.org, Jan Kara , Kees Cook , Greg Kroah-Hartman , linux-pci@vger.kernel.org, linux-mm@kvack.org, Jason Gunthorpe , =?utf-8?B?SsOpcsO0bWU=?= Glisse , John Hubbard , Bjorn Helgaas , Daniel Vetter , Dan Williams , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, Oliver O'Halloran , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= Subject: Re: [PATCH 1/2] PCI: also set up legacy files only after sysfs init Message-ID: <20210204222407.pkx7wvmcvugdwqdd@pali> References: <20210204165831.2703772-2-daniel.vetter@ffwll.ch> <20210204215019.GA104698@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210204215019.GA104698@bjorn-Precision-5520> User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thursday 04 February 2021 15:50:19 Bjorn Helgaas wrote: > [+cc Oliver, Pali, Krzysztof] Just to note that extending or using sysfs_initialized introduces another race condition into kernel code which results in PCI fatal errors. Details are in email discussion which Bjorn already sent. > s/also/Also/ in subject > > On Thu, Feb 04, 2021 at 05:58:30PM +0100, Daniel Vetter wrote: > > We are already doing this for all the regular sysfs files on PCI > > devices, but not yet on the legacy io files on the PCI buses. Thus far > > now problem, but in the next patch I want to wire up iomem revoke > > support. That needs the vfs up an running already to make so that > > iomem_get_mapping() works. > > s/now problem/no problem/ > s/an running/and running/ > s/so that/sure that/ ? > > iomem_get_mapping() doesn't exist; I don't know what that should be. > > > Wire it up exactly like the existing code. Note that > > pci_remove_legacy_files() doesn't need a check since the one for > > pci_bus->legacy_io is sufficient. > > I'm not sure exactly what you mean by "the existing code." I could > probably figure it out, but it would save time to mention the existing > function here. > > This looks like another instance where we should really apply Oliver's > idea of converting these to attribute_groups [1]. > > The cover letter mentions options discussed with Greg in [2], but I > don't think the "sysfs_initialized" hack vs attribute_groups was part > of that discussion. > > It's not absolutely a show-stopper, but it *is* a shame to extend the > sysfs_initialized hack if attribute_groups could do this more cleanly > and help solve more than one issue. > > Bjorn > > [1] https://lore.kernel.org/r/CAOSf1CHss03DBSDO4PmTtMp0tCEu5kScn704ZEwLKGXQzBfqaA@mail.gmail.com > [2] https://lore.kernel.org/dri-devel/CAKMK7uGrdDrbtj0OyzqQc0CGrQwc2F3tFJU9vLfm2jjufAZ5YQ@mail.gmail.com/ > > > Signed-off-by: Daniel Vetter > > Cc: Stephen Rothwell > > Cc: Jason Gunthorpe > > Cc: Kees Cook > > Cc: Dan Williams > > Cc: Andrew Morton > > Cc: John Hubbard > > Cc: Jérôme Glisse > > Cc: Jan Kara > > Cc: Dan Williams > > Cc: Greg Kroah-Hartman > > Cc: linux-mm@kvack.org > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-samsung-soc@vger.kernel.org > > Cc: linux-media@vger.kernel.org > > Cc: Bjorn Helgaas > > Cc: linux-pci@vger.kernel.org > > --- > > drivers/pci/pci-sysfs.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > > index fb072f4b3176..0c45b4f7b214 100644 > > --- a/drivers/pci/pci-sysfs.c > > +++ b/drivers/pci/pci-sysfs.c > > @@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b) > > { > > int error; > > > > + if (!sysfs_initialized) > > + return; > > + > > b->legacy_io = kcalloc(2, sizeof(struct bin_attribute), > > GFP_ATOMIC); > > if (!b->legacy_io) > > @@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev) > > static int __init pci_sysfs_init(void) > > { > > struct pci_dev *pdev = NULL; > > + struct pci_bus *pbus = NULL; > > int retval; > > > > sysfs_initialized = 1; > > @@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void) > > } > > } > > > > + while ((pbus = pci_find_next_bus(pbus))) > > + pci_create_legacy_files(pbus); > > + > > return 0; > > } > > late_initcall(pci_sysfs_init); > > -- > > 2.30.0 > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel