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[23.128.96.18]) by mx.google.com with ESMTP id l27si2822074ejg.613.2020.07.16.04.04.59; Thu, 16 Jul 2020 04:05:22 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=XZ3ghstQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728100AbgGPLEe (ORCPT + 99 others); Thu, 16 Jul 2020 07:04:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:57816 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726350AbgGPLE0 (ORCPT ); Thu, 16 Jul 2020 07:04:26 -0400 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 DD050206C1; Thu, 16 Jul 2020 11:04:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594897466; bh=+BWVY0M3N/+15ufR38OrEUTc1Bb2RjAi8T49lW+iWL8=; h=Date:From:To:Subject:From; b=XZ3ghstQul/6AUijuC/HF36st0HagoPiJKiYdr917iYAwsYj5Lq309VEAr8GfufaE 2PgflYqIlXipTbIdIU3kVDIkLxigL7k44bOLnbw9og7hARnW83HbpdQ6QMCvzMrCyG oq1yNp95hHiVxZzux04iJAundJ7ecYsgp1lDaITs= Received: by pali.im (Postfix) id DDFEFE7A; Thu, 16 Jul 2020 13:04:23 +0200 (CEST) Date: Thu, 16 Jul 2020 13:04:23 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: PCI: Race condition in pci_create_sysfs_dev_files Message-ID: <20200716110423.xtfyb3n6tn5ixedh@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? 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)