From patchwork Fri Feb 15 22:22:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alex Williamson X-Patchwork-Id: 10816041 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3D91B1575 for ; Fri, 15 Feb 2019 22:22:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2AB3930114 for ; Fri, 15 Feb 2019 22:22:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1EA8E3011D; Fri, 15 Feb 2019 22:22:18 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A57A330114 for ; Fri, 15 Feb 2019 22:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728593AbfBOWWQ (ORCPT ); Fri, 15 Feb 2019 17:22:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39648 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726000AbfBOWWQ (ORCPT ); Fri, 15 Feb 2019 17:22:16 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 91AE7C04D293; Fri, 15 Feb 2019 22:22:15 +0000 (UTC) Received: from gimli.home (ovpn-116-24.phx2.redhat.com [10.3.116.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 14F7D101E841; Fri, 15 Feb 2019 22:22:13 +0000 (UTC) Subject: [PATCH] PCI: Fix "try" semantics of bus and slot reset From: Alex Williamson To: linux-pci@vger.kernel.org Cc: linux-kernel@vger.kernel.org, bhelgaas@google.com, hch@lst.de, okaya@kernel.org Date: Fri, 15 Feb 2019 15:22:12 -0700 Message-ID: <155026928113.22063.9297300688702894514.stgit@gimli.home> User-Agent: StGit/0.19-dirty MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 15 Feb 2019 22:22:15 +0000 (UTC) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The commit referenced below introduced device locking around save and restore of state for each device during a PCI bus "try" reset, making it decidely non-"try" and prone to deadlock in the event that a device is already locked. Restore __pci_reset_bus() and __pci_reset_slot() to their advertised locking semantics by pushing the save and restore functions into the branch where the entire tree is already locked. Extend the helper function names with "_locked" and update the comment to reflect this calling requirement. Fixes: b014e96d1abb ("PCI: Protect pci_error_handlers->reset_notify() usage with device_lock()") Signed-off-by: Alex Williamson --- drivers/pci/pci.c | 53 ++++++++++++++++++++++++++--------------------------- 1 file changed, 26 insertions(+), 27 deletions(-) diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c25acace7d91..870834cb6672 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5058,39 +5058,42 @@ static int pci_slot_trylock(struct pci_slot *slot) return 0; } -/* Save and disable devices from the top of the tree down */ -static void pci_bus_save_and_disable(struct pci_bus *bus) +/* + * Save and disable devices from the top of the tree down while holding + * the @dev mutex lock for the entire tree. + */ +static void pci_bus_save_and_disable_locked(struct pci_bus *bus) { struct pci_dev *dev; list_for_each_entry(dev, &bus->devices, bus_list) { - pci_dev_lock(dev); pci_dev_save_and_disable(dev); - pci_dev_unlock(dev); if (dev->subordinate) - pci_bus_save_and_disable(dev->subordinate); + pci_bus_save_and_disable_locked(dev->subordinate); } } /* - * Restore devices from top of the tree down - parent bridges need to be - * restored before we can get to subordinate devices. + * Restore devices from top of the tree down while holding @dev mutex lock + * for the entire tree. Parent bridges need to be restored before we can + * get to subordinate devices. */ -static void pci_bus_restore(struct pci_bus *bus) +static void pci_bus_restore_locked(struct pci_bus *bus) { struct pci_dev *dev; list_for_each_entry(dev, &bus->devices, bus_list) { - pci_dev_lock(dev); pci_dev_restore(dev); - pci_dev_unlock(dev); if (dev->subordinate) - pci_bus_restore(dev->subordinate); + pci_bus_restore_locked(dev->subordinate); } } -/* Save and disable devices from the top of the tree down */ -static void pci_slot_save_and_disable(struct pci_slot *slot) +/* + * Save and disable devices from the top of the tree down while holding + * the @dev mutex lock for the entire tree. + */ +static void pci_slot_save_and_disable_locked(struct pci_slot *slot) { struct pci_dev *dev; @@ -5099,26 +5102,25 @@ static void pci_slot_save_and_disable(struct pci_slot *slot) continue; pci_dev_save_and_disable(dev); if (dev->subordinate) - pci_bus_save_and_disable(dev->subordinate); + pci_bus_save_and_disable_locked(dev->subordinate); } } /* - * Restore devices from top of the tree down - parent bridges need to be - * restored before we can get to subordinate devices. + * Restore devices from top of the tree down while holding @dev mutex lock + * for the entire tree. Parent bridges need to be restored before we can + * get to subordinate devices. */ -static void pci_slot_restore(struct pci_slot *slot) +static void pci_slot_restore_locked(struct pci_slot *slot) { struct pci_dev *dev; list_for_each_entry(dev, &slot->bus->devices, bus_list) { if (!dev->slot || dev->slot != slot) continue; - pci_dev_lock(dev); pci_dev_restore(dev); - pci_dev_unlock(dev); if (dev->subordinate) - pci_bus_restore(dev->subordinate); + pci_bus_restore_locked(dev->subordinate); } } @@ -5177,16 +5179,15 @@ static int __pci_reset_slot(struct pci_slot *slot) if (rc) return rc; - pci_slot_save_and_disable(slot); - if (pci_slot_trylock(slot)) { + pci_slot_save_and_disable_locked(slot); might_sleep(); rc = pci_reset_hotplug_slot(slot->hotplug, 0); + pci_slot_restore_locked(slot); pci_slot_unlock(slot); } else rc = -EAGAIN; - pci_slot_restore(slot); return rc; } @@ -5273,17 +5274,15 @@ static int __pci_reset_bus(struct pci_bus *bus) if (rc) return rc; - pci_bus_save_and_disable(bus); - if (pci_bus_trylock(bus)) { + pci_bus_save_and_disable_locked(bus); might_sleep(); rc = pci_bridge_secondary_bus_reset(bus->self); + pci_bus_restore_locked(bus); pci_bus_unlock(bus); } else rc = -EAGAIN; - pci_bus_restore(bus); - return rc; }