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=-6.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 223E2C4338F for ; Fri, 30 Jul 2021 19:50:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 02BBD60F9B for ; Fri, 30 Jul 2021 19:50:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230408AbhG3TuU (ORCPT ); Fri, 30 Jul 2021 15:50:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:54252 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230402AbhG3TuU (ORCPT ); Fri, 30 Jul 2021 15:50:20 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 04FAA60230; Fri, 30 Jul 2021 19:50:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627674615; bh=KzWfUjXOKFMxakJ70IwzSJ9xOJKRqhVhpS6tY3Ge/Jw=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=DCcKUjcwlqwnG3gHktNa5qiz+s2cMXHLVhO/Be+n3VJlbeCNa94qqIzE8MKClb1ln qNEdbBnKCtfDTLkNjcRcneWa0GZwDE1SkAZdbok+YgtN2QNHCeOo0pa7yStd48vbhw EYGrmPhN0RHFli8IZayFu1mwImBXP930afu/dToq4+X8ERFLjB1iMCh3e0MuSbd8uO aCLmkHNjmWM4vO+kCeS5DGdVEJYJbIVB1vcC486f+NMB4w+XK52LWJMLtMVDiLanHK WdNdy4sA5gMXjDz42HvmXpXYqnaKnpukJ4MyaNIlMpZBu9Lrknk8BEVnN12lRZ0K/N pIrfzPD1VqmqQ== Date: Fri, 30 Jul 2021 14:50:13 -0500 From: Bjorn Helgaas To: Greg Kroah-Hartman Cc: Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Bjorn Helgaas , Dan Williams , Daniel Vetter , Kees Cook , Pali =?iso-8859-1?Q?Roh=E1r?= , Oliver O'Halloran , linux-pci@vger.kernel.org Subject: Re: [PATCH v3 0/2] Allow deferred execution of iomem_get_mapping() Message-ID: <20210730195013.GA1090988@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Jul 30, 2021 at 07:06:26AM +0200, Greg Kroah-Hartman wrote: > On Thu, Jul 29, 2021 at 11:32:33PM +0000, Krzysztof Wilczyński wrote: > > Hello, > > > > At the moment, the dependency on iomem_get_mapping() that is currently > > used in the pci_create_resource_files() and pci_create_legacy_files() > > stops us from completely retiring the late_initcall() that is used to > > invoke pci_sysfs_init() when creating sysfs object for PCI devices. > > > > This dependency on iomem_get_mapping() stops us from retiring the > > late_initcall at the moment as when we convert dynamically added sysfs > > objects, that are primarily added in the pci_create_resource_files() and > > pci_create_legacy_files(), as these attributes are added before the VFS > > completes its initialisation, and since most of the PCI devices are > > typically enumerated in subsys_initcall this leads to a failure and an > > Oops related to iomem_get_mapping() access. > > > > See relevant conversations: > > https://lore.kernel.org/linux-pci/20210204165831.2703772-1-daniel.vetter@ffwll.ch/ > > https://lore.kernel.org/linux-pci/20210313215747.GA2394467@bjorn-Precision-5520/ > > > > After some deliberation about the problem at hand, Dan Williams > > suggested a solution to the problem, as per: > > https://lore.kernel.org/linux-pci/CAPcyv4i0y_4cMGEpNVShLUyUk3nyWH203Ry3S87BqnDJE0Rmxg@mail.gmail.com/ > > > > The idea is to defer execution of the iomem_get_mapping() to only when > > the sysfs open callback is run, and thus removing the reliance of > > fs_initcalls to complete before any other sub-system that uses the > > iomem_get_mapping(). > > > > Currently, the PCI sub-system will benefit the most from this change > > allowing for it to complete the transition from dynamically created to > > static sysfs objects. > > > > This series aims to take Dan Williams' idea through the finish line. > > > > Related to: > > https://lore.kernel.org/linux-pci/20210527205845.GA1421476@bjorn-Precision-5520/ > > https://lore.kernel.org/linux-pci/20210507102706.7658-1-danijel.slivka@amd.com/ > > https://lore.kernel.org/linux-pci/20200716110423.xtfyb3n6tn5ixedh@pali/ > > > > Krzysztof > > > > No objection from me on these, Bjorn, mind if I take them through my > driver core tree? That'd be great! Is your tree immutable? I'm hoping we can take advantage of this to get rid of pci_sysfs_init(), which will fix a race that people seem to be hitting frequently now [1]. I think Krzysztof is getting pretty close. [1] https://lore.kernel.org/r/m3eebg9puj.fsf@t19.piap.pl