From patchwork Fri Aug 16 16:50:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergei Miroshnichenko X-Patchwork-Id: 1148333 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pci-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=yadro.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=yadro.com header.i=@yadro.com header.b="LJT+ElBP"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 4698Tt40tsz9sML for ; Sat, 17 Aug 2019 02:51:14 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726557AbfHPQvO (ORCPT ); Fri, 16 Aug 2019 12:51:14 -0400 Received: from mta-02.yadro.com ([89.207.88.252]:51292 "EHLO mta-01.yadro.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725956AbfHPQvN (ORCPT ); Fri, 16 Aug 2019 12:51:13 -0400 Received: from localhost (unknown [127.0.0.1]) by mta-01.yadro.com (Postfix) with ESMTP id 9CD5D42EDE; Fri, 16 Aug 2019 16:51:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=yadro.com; h= content-type:content-type:content-transfer-encoding:mime-version :references:in-reply-to:x-mailer:message-id:date:date:subject :subject:from:from:received:received:received; s=mta-01; t= 1565974270; x=1567788671; bh=DAI3gRiSUwjuoITu07sLg9XHSeUz3NxP+X7 I4SwWqEw=; b=LJT+ElBPPsS3Tz1AYyCgd29UF/orAeDovDCYJsxp5Hc4jIZDvSp QDY+e7yG6OUm6GaeJPPvmgCdTKVF2kp85VA/5xWbG/zWgohuonJI6kJzhvnvQOHh Mp3aH/bP5/EoQFEpaEt0YyghOmMMIJaGW84+RU+6pZOm/mb/3kUc3JaY= X-Virus-Scanned: amavisd-new at yadro.com Received: from mta-01.yadro.com ([127.0.0.1]) by localhost (mta-01.yadro.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id eLmb1s1nUXNs; Fri, 16 Aug 2019 19:51:10 +0300 (MSK) Received: from T-EXCH-02.corp.yadro.com (t-exch-02.corp.yadro.com [172.17.10.102]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mta-01.yadro.com (Postfix) with ESMTPS id D7BF5412D2; Fri, 16 Aug 2019 19:51:08 +0300 (MSK) Received: from NB-148.yadro.com (172.17.15.60) by T-EXCH-02.corp.yadro.com (172.17.10.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.669.32; Fri, 16 Aug 2019 19:51:08 +0300 From: Sergey Miroshnichenko To: , CC: Bjorn Helgaas , , Sergey Miroshnichenko , Srinath Mannam , Marta Rybczynska Subject: [PATCH v5 01/23] PCI: Fix race condition in pci_enable/disable_device() Date: Fri, 16 Aug 2019 19:50:39 +0300 Message-ID: <20190816165101.911-2-s.miroshnichenko@yadro.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190816165101.911-1-s.miroshnichenko@yadro.com> References: <20190816165101.911-1-s.miroshnichenko@yadro.com> MIME-Version: 1.0 X-Originating-IP: [172.17.15.60] X-ClientProxiedBy: T-EXCH-01.corp.yadro.com (172.17.10.101) To T-EXCH-02.corp.yadro.com (172.17.10.102) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org This is a yet another approach to fix an old [1-2] concurrency issue, when: - two or more devices are being hot-added into a bridge which was initially empty; - a bridge with two or more devices is being hot-added; - during boot, if BIOS/bootloader/firmware doesn't pre-enable bridges. The problem is that a bridge is reported as enabled before the MEM/IO bits are actually written to the PCI_COMMAND register, so another driver thread starts memory requests through the not-yet-enabled bridge: CPU0 CPU1 pci_enable_device_mem() pci_enable_device_mem() pci_enable_bridge() pci_enable_bridge() pci_is_enabled() return false; atomic_inc_return(enable_cnt) Start actual enabling the bridge ... pci_is_enabled() ... return true; ... Start memory requests <-- FAIL ... Set the PCI_COMMAND_MEMORY bit <-- Must wait for this Protect the pci_enable/disable_device() and pci_enable_bridge(), which is similar to the previous solution from commit 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges"), but adding a per-device mutexes and preventing the dev->enable_cnt from from incrementing early. CC: Srinath Mannam CC: Marta Rybczynska Signed-off-by: Sergey Miroshnichenko [1] https://lore.kernel.org/linux-pci/1501858648-22228-1-git-send-email-srinath.mannam@broadcom.com/T/#u [RFC PATCH v3] pci: Concurrency issue during pci enable bridge [2] https://lore.kernel.org/linux-pci/744877924.5841545.1521630049567.JavaMail.zimbra@kalray.eu/T/#u [RFC PATCH] nvme: avoid race-conditions when enabling devices --- drivers/pci/pci.c | 26 ++++++++++++++++++++++---- drivers/pci/probe.c | 1 + include/linux/pci.h | 1 + 3 files changed, 24 insertions(+), 4 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 1b27b5af3d55..e7f8c354e644 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1645,6 +1645,8 @@ static void pci_enable_bridge(struct pci_dev *dev) struct pci_dev *bridge; int retval; + mutex_lock(&dev->enable_mutex); + bridge = pci_upstream_bridge(dev); if (bridge) pci_enable_bridge(bridge); @@ -1652,6 +1654,7 @@ static void pci_enable_bridge(struct pci_dev *dev) if (pci_is_enabled(dev)) { if (!dev->is_busmaster) pci_set_master(dev); + mutex_unlock(&dev->enable_mutex); return; } @@ -1660,11 +1663,14 @@ static void pci_enable_bridge(struct pci_dev *dev) pci_err(dev, "Error enabling bridge (%d), continuing\n", retval); pci_set_master(dev); + mutex_unlock(&dev->enable_mutex); } static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) { struct pci_dev *bridge; + /* Enable-locking of bridges is performed within the pci_enable_bridge() */ + bool need_lock = !dev->subordinate; int err; int i, bars = 0; @@ -1680,8 +1686,13 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); } - if (atomic_inc_return(&dev->enable_cnt) > 1) + if (need_lock) + mutex_lock(&dev->enable_mutex); + if (pci_is_enabled(dev)) { + if (need_lock) + mutex_unlock(&dev->enable_mutex); return 0; /* already enabled */ + } bridge = pci_upstream_bridge(dev); if (bridge) @@ -1696,8 +1707,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags) bars |= (1 << i); err = do_pci_enable_device(dev, bars); - if (err < 0) - atomic_dec(&dev->enable_cnt); + if (err >= 0) + atomic_inc(&dev->enable_cnt); + if (need_lock) + mutex_unlock(&dev->enable_mutex); return err; } @@ -1941,15 +1954,20 @@ void pci_disable_device(struct pci_dev *dev) if (dr) dr->enabled = 0; + mutex_lock(&dev->enable_mutex); dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0, "disabling already-disabled device"); - if (atomic_dec_return(&dev->enable_cnt) != 0) + if (atomic_dec_return(&dev->enable_cnt) != 0) { + mutex_unlock(&dev->enable_mutex); return; + } do_pci_disable_device(dev); dev->is_busmaster = 0; + + mutex_unlock(&dev->enable_mutex); } EXPORT_SYMBOL(pci_disable_device); diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index a3c7338fad86..2e58ece820e8 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2427,6 +2427,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus) INIT_LIST_HEAD(&dev->bus_list); dev->dev.type = &pci_dev_type; dev->bus = pci_bus_get(bus); + mutex_init(&dev->enable_mutex); return dev; } diff --git a/include/linux/pci.h b/include/linux/pci.h index 9e700d9f9f28..d3a72159722d 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -425,6 +425,7 @@ struct pci_dev { unsigned int no_vf_scan:1; /* Don't scan for VFs after IOV enablement */ pci_dev_flags_t dev_flags; atomic_t enable_cnt; /* pci_enable_device has been called */ + struct mutex enable_mutex; u32 saved_config_space[16]; /* Config space saved at suspend time */ struct hlist_head saved_cap_space;