From patchwork Thu Jun 11 11:12:14 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yijing Wang X-Patchwork-Id: 6587691 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: patchwork-linux-pci@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id F3D1FC0020 for ; Thu, 11 Jun 2015 11:17:29 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 70F9A204D1 for ; Thu, 11 Jun 2015 11:17:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49C2E2047B for ; Thu, 11 Jun 2015 11:17:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751047AbbFKLR0 (ORCPT ); Thu, 11 Jun 2015 07:17:26 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:61315 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbbFKLRZ (ORCPT ); Thu, 11 Jun 2015 07:17:25 -0400 Received: from 172.24.2.119 (EHLO SZXEML429-HUB.china.huawei.com) ([172.24.2.119]) by szxrg01-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id CPJ51265; Thu, 11 Jun 2015 19:17:07 +0800 (CST) Received: from localhost.localdomain (10.175.100.166) by SZXEML429-HUB.china.huawei.com (10.82.67.184) with Microsoft SMTP Server id 14.3.158.1; Thu, 11 Jun 2015 19:16:55 +0800 From: Yijing Wang To: CC: , , Yijing Wang Subject: [PATCH] PCI: Use a local mutex instead of pci_bus_sem to avoid deadlock Date: Thu, 11 Jun 2015 19:12:14 +0800 Message-ID: <1434021134-6519-1-git-send-email-wangyijing@huawei.com> X-Mailer: git-send-email 1.7.1 MIME-Version: 1.0 X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Rajat Jain reported a deadlock when a hierarchical hot plug thread and aer recovery thread both run. https://lkml.org/lkml/2015/3/11/861 thread 1: pciehp_enable_slot() pciehp_configure_device() pci_bus_add_devices() device_attach(dev) device_lock(dev) //acquire device mutex successfully ... pciehp_probe(dev) __pci_hp_register() pci_create_slot() down_write(pci_bus_sem) //deadlock here thread 2: aer_isr_one_error() aer_process_err_device() do_recovery() broadcast_error_message() pci_walk_bus() down_read(&pci_bus_sem) //acquire pci_bus_sem successfully report_error_detected(dev) device_lock(dev) // deadlock here Now we use pci_bus_sem to protect pci_slot creation and destroy, it's unnecessary. We could introduce a new local mutex instead of pci_bus_sem to avoid the deadlock. Signed-off-by: Yijing Wang Tested-by: Guenter Roeck --- drivers/pci/slot.c | 11 ++++++----- 1 files changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c index 396c200..feb08de 100644 --- a/drivers/pci/slot.c +++ b/drivers/pci/slot.c @@ -14,6 +14,7 @@ struct kset *pci_slots_kset; EXPORT_SYMBOL_GPL(pci_slots_kset); +static DEFINE_MUTEX(pci_slot_mutex); static ssize_t pci_slot_attr_show(struct kobject *kobj, struct attribute *attr, char *buf) @@ -195,7 +196,7 @@ static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr) { struct pci_slot *slot; /* - * We already hold pci_bus_sem so don't worry + * We already hold pci_slot_mutex so don't worry */ list_for_each_entry(slot, &parent->slots, list) if (slot->number == slot_nr) { @@ -253,7 +254,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr, int err = 0; char *slot_name = NULL; - down_write(&pci_bus_sem); + mutex_lock(&pci_slot_mutex); if (slot_nr == -1) goto placeholder; @@ -310,7 +311,7 @@ placeholder: out: kfree(slot_name); - up_write(&pci_bus_sem); + mutex_unlock(&pci_slot_mutex); return slot; err: kfree(slot); @@ -332,9 +333,9 @@ void pci_destroy_slot(struct pci_slot *slot) dev_dbg(&slot->bus->dev, "dev %02x, dec refcount to %d\n", slot->number, atomic_read(&slot->kobj.kref.refcount) - 1); - down_write(&pci_bus_sem); + mutex_lock(&pci_slot_mutex); kobject_put(&slot->kobj); - up_write(&pci_bus_sem); + mutex_unlock(&pci_slot_mutex); } EXPORT_SYMBOL_GPL(pci_destroy_slot);