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=-10.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 1D0F8C2D0A3 for ; Wed, 4 Nov 2020 16:46:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9E28206DB for ; Wed, 4 Nov 2020 16:46:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604508411; bh=8tGL6oAMB7wNHUqKWEHZkOjh160kXJWJi2X2a6dNbEQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=boyOO/ECvME6kaMQx2vAdR5kvhxjMTj2FwUQDeGp4DAXBYH43OWM9sK/u2Um6CRBX IWmzGb4IlOhcX4r9O5KV1ltblzxLI/iMKLzQJo1EkCVRbpOvt91TrbChi+50dp4Yae mcTKSHHGwjBYfnwnpUgHttXbu5jKpR/g/ayk1qMY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731377AbgKDQqv (ORCPT ); Wed, 4 Nov 2020 11:46:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:44112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730987AbgKDQqu (ORCPT ); Wed, 4 Nov 2020 11:46:50 -0500 Received: from pali.im (pali.im [31.31.79.79]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CD6A0206CA; Wed, 4 Nov 2020 16:46:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604508410; bh=8tGL6oAMB7wNHUqKWEHZkOjh160kXJWJi2X2a6dNbEQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hOgdTjs+nwzvdCfQagJ17N1ywbLm/ip4XjMB5SKjmGVacXB9WGZRdsYe8FHdQyPdf vHNpC3mtnuUeXiozagw/6T4SaZxwTQRciQO+0b2ZF+53fkl69gGudVpfAJXdAsClWc Tq8xDNYxuU4GSrtmbFC54Frj4gMkh1/H582iOvBw= Received: by pali.im (Postfix) id 56D8A53E; Wed, 4 Nov 2020 17:46:47 +0100 (CET) Date: Wed, 4 Nov 2020 17:46:47 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Bjorn Helgaas Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Lorenzo Pieralisi , Gregory Clement , Andrew Lunn , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Yinghai Lu Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files Message-ID: <20201104164647.pctgyk2cbhjcq65z@pali> References: <20200909112850.hbtgkvwqy2rlixst@pali> <20201006222222.GA3221382@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201006222222.GA3221382@bjorn-Precision-5520> User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tuesday 06 October 2020 17:22:22 Bjorn Helgaas wrote: > It's not obvious from the code why we need pci_sysfs_init(), but > Yinghai hinted [1] that we need to create sysfs after assigning > resources. I experimented by removing pci_sysfs_init() and skipping > the ROM BAR sizing. In that case, we create sysfs files in > pci_bus_add_device() and later assign space for the ROM BAR, so we > fail to create the "rom" sysfs file. > > The current solution to that is to delay the sysfs files until > pci_sysfs_init(), a late_initcall(), which runs after resource > assignments. But I think it would be better if we could create the > sysfs file when we assign the BAR. Then we could get rid of the > late_initcall() and that implicit ordering requirement. > > But I haven't tried to code it up, so it's probably more complicated > than this. I guess ideally we would assign all the resources before > pci_bus_add_device(). If we could do that, we could just remove > pci_sysfs_init() and everything would just work, but I think that's a > HUGE can of worms. > > [1] https://lore.kernel.org/linux-pci/CAE9FiQWBXHgz-gWCmpWLaBOfQQJwtRZemV6Ut9GVw_KJ-dTGTA@mail.gmail.com/ I found out that pci_sysfs_init() function was introduced in kernel version 2.6.10 by this historic commit: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=f6d553444da20cd1e44f2c4864c2d0c56c934e0a So it was really due to PCI ROM BAR and accessing it from sysfs.