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=-7.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 E83F6C4363D for ; Mon, 5 Oct 2020 13:54:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1C0820774 for ; Mon, 5 Oct 2020 13:54:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601906074; bh=BLBK9GcYOTgyQfZfGPZdQxfDZtCxXiUa4Ew5RCkk7ac=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=I26hcxz4exvJPa85xSlp2GvdyUSE//cw/bJy9L903XAgfqIi9QhMqJ8FG1dyFAfyV 6RaVwwdz32P8ScDRTN64nNXmcKasLyZDmlVjfT3p3CW/HFjlrY3yiUUErGDGjpAjBD KfWExAJsLWvbeMQnw99WS3uJjsKsOirk54JadjZQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726060AbgJENyd (ORCPT ); Mon, 5 Oct 2020 09:54:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:48890 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgJENyc (ORCPT ); Mon, 5 Oct 2020 09:54:32 -0400 Received: from localhost (170.sub-72-107-125.myvzw.com [72.107.125.170]) (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 E69D920774; Mon, 5 Oct 2020 13:54:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601906071; bh=BLBK9GcYOTgyQfZfGPZdQxfDZtCxXiUa4Ew5RCkk7ac=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=xWXO9k8hotDaxWVegw42sZpMZHxR9w6VJRiTgbcv0UFmIX1f7UmK86u96vyaxMFUU 2va33gP+csqMm1D9/XmR+yd05OkJZyHHZ0xRmyd0WSPdsc0lNSWNrYdwu2hMCv8c31 dZDWFKPdtE1Z4wxurBkxFH6Ykjju6x2QzlkWFQ/k= Date: Mon, 5 Oct 2020 08:54:29 -0500 From: Bjorn Helgaas To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Lorenzo Pieralisi , Gregory Clement , Andrew Lunn Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files Message-ID: <20201005135429.GA3007344@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20201005082018.rowqpfifyyrilxma@pali> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2020 at 10:20:18AM +0200, Pali Rohár wrote: > PING? Sorry, I guess nobody has had the right combination of time, interest, and knowledge to work on this. I'll try to take a look this week. > On Wednesday 09 September 2020 13:28:50 Pali Rohár wrote: > > Hello! I'm adding more people to loop. > > > > Can somebody look at these race conditions and my patch? > > > > On Friday 14 August 2020 10:08:24 Pali Rohár wrote: > > > Hello! I would like to remind this issue which I reported month ago. > > > > > > On Thursday 16 July 2020 13:04:23 Pali Rohár wrote: > > > > Hello Bjorn! > > > > > > > > I see following error message in dmesg which looks like a race condition: > > > > > > > > sysfs: cannot create duplicate filename '/devices/platform/soc/d0070000.pcie/pci0000:00/0000:00:00.0/config' > > > > > > > > I looked at it deeper and found out that in PCI subsystem code is race > > > > condition between pci_bus_add_device() and pci_sysfs_init() calls. Both > > > > of these functions calls pci_create_sysfs_dev_files() and calling this > > > > function more times for same pci device throws above error message. > > > > > > > > There can be two different race conditions: > > > > > > > > 1. pci_bus_add_device() called pcibios_bus_add_device() or > > > > pci_fixup_device() but have not called pci_create_sysfs_dev_files() yet. > > > > Meanwhile pci_sysfs_init() is running and pci_create_sysfs_dev_files() > > > > was called for newly registered device. In this case function > > > > pci_create_sysfs_dev_files() is called two times, ones from > > > > pci_bus_add_device() and once from pci_sysfs_init(). > > > > > > > > 2. pci_sysfs_init() is called. It first sets sysfs_initialized to 1 > > > > which unblock calling pci_create_sysfs_dev_files(). Then another bus > > > > registers new PCI device and calls pci_bus_add_device() which calls > > > > pci_create_sysfs_dev_files() and registers sysfs files. Function > > > > pci_sysfs_init() continues execution and calls function > > > > pci_create_sysfs_dev_files() also for this newly registered device. So > > > > pci_create_sysfs_dev_files() is again called two times. > > > > > > > > > > > > I workaround both race conditions I created following hack patch. After > > > > applying it I'm not getting that 'sysfs: cannot create duplicate filename' > > > > error message anymore. > > > > > > > > Can you look at it how to fix both race conditions in proper way? > > > > > > Is this workaround diff enough? Or are you going to prepare something better? > > > > > > Please let me know if I should send this diff as regular patch. > > > > > > > > > > > diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c > > > > index 8e40b3e6da77..691be2258c4e 100644 > > > > --- a/drivers/pci/bus.c > > > > +++ b/drivers/pci/bus.c > > > > @@ -316,7 +316,7 @@ void pci_bus_add_device(struct pci_dev *dev) > > > > */ > > > > pcibios_bus_add_device(dev); > > > > pci_fixup_device(pci_fixup_final, dev); > > > > - pci_create_sysfs_dev_files(dev); > > > > + pci_create_sysfs_dev_files(dev, false); > > > > pci_proc_attach_device(dev); > > > > pci_bridge_d3_update(dev); > > > > > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c > > > > index 6d78df981d41..b0c4852a51dd 100644 > > > > --- a/drivers/pci/pci-sysfs.c > > > > +++ b/drivers/pci/pci-sysfs.c > > > > @@ -1328,13 +1328,13 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev) > > > > return retval; > > > > } > > > > > > > > -int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev) > > > > +int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev, bool sysfs_initializing) > > > > { > > > > int retval; > > > > int rom_size; > > > > struct bin_attribute *attr; > > > > > > > > - if (!sysfs_initialized) > > > > + if (!sysfs_initializing && !sysfs_initialized) > > > > return -EACCES; > > > > > > > > if (pdev->cfg_size > PCI_CFG_SPACE_SIZE) > > > > @@ -1437,18 +1437,21 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev) > > > > static int __init pci_sysfs_init(void) > > > > { > > > > struct pci_dev *pdev = NULL; > > > > - int retval; > > > > + int retval = 0; > > > > > > > > - sysfs_initialized = 1; > > > > for_each_pci_dev(pdev) { > > > > - retval = pci_create_sysfs_dev_files(pdev); > > > > + if (!pci_dev_is_added(pdev)) > > > > + continue; > > > > + retval = pci_create_sysfs_dev_files(pdev, true); > > > > if (retval) { > > > > pci_dev_put(pdev); > > > > - return retval; > > > > + goto out; > > > > } > > > > } > > > > > > > > - return 0; > > > > +out: > > > > + sysfs_initialized = 1; > > > > + return retval; > > > > } > > > > late_initcall(pci_sysfs_init); > > > > > > > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > > > > index 6d3f75867106..304294c7171e 100644 > > > > --- a/drivers/pci/pci.h > > > > +++ b/drivers/pci/pci.h > > > > @@ -19,7 +19,7 @@ bool pcie_cap_has_rtctl(const struct pci_dev *dev); > > > > > > > > /* Functions internal to the PCI core code */ > > > > > > > > -int pci_create_sysfs_dev_files(struct pci_dev *pdev); > > > > +int pci_create_sysfs_dev_files(struct pci_dev *pdev, bool sysfs_initializing); > > > > void pci_remove_sysfs_dev_files(struct pci_dev *pdev); > > > > #if !defined(CONFIG_DMI) && !defined(CONFIG_ACPI) > > > > static inline void pci_create_firmware_label_files(struct pci_dev *pdev) > > > >