From patchwork Fri Jan 15 18:30:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 364219 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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham 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 67D1CC433E0 for ; Fri, 15 Jan 2021 18:31:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3900323A5A for ; Fri, 15 Jan 2021 18:31:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726519AbhAOSbe (ORCPT ); Fri, 15 Jan 2021 13:31:34 -0500 Received: from cloudserver094114.home.pl ([79.96.170.134]:59974 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726151AbhAOSbe (ORCPT ); Fri, 15 Jan 2021 13:31:34 -0500 Received: from 89-64-81-100.dynamic.chello.pl (89.64.81.100) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.537) id 3e720a1ca388cf11; Fri, 15 Jan 2021 19:30:51 +0100 From: "Rafael J. Wysocki" To: Greg Kroah-Hartman Cc: LKML , Linux PM , Stephan Gerhold , Saravana Kannan Subject: [PATCH v2] driver core: Extend device_is_dependent() Date: Fri, 15 Jan 2021 19:30:51 +0100 Message-ID: <17705994.d592GUb2YH@kreacher> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: Rafael J. Wysocki If the device passed as the target (second argument) to device_is_dependent() is not completely registered (that is, it has been initialized, but not added yet), but the parent pointer of it is set, it may be missing from the list of the parent's children and device_for_each_child() called by device_is_dependent() cannot be relied on to catch that dependency. For this reason, modify device_is_dependent() to check the ancestors of the target device by following its parent pointer in addition to the device_for_each_child() walk. Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support") Signed-off-by: Rafael J. Wysocki Reported-by: Stephan Gerhold Tested-by: Stephan Gerhold Reviewed-by: Saravana Kannan --- -> v2: * Improve the changelog. * Add a comment to explain the reason for the extra check. * Add tags. No code changes. --- drivers/base/core.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) Index: linux-pm/drivers/base/core.c =================================================================== --- linux-pm.orig/drivers/base/core.c +++ linux-pm/drivers/base/core.c @@ -208,6 +208,16 @@ int device_links_read_lock_held(void) #endif #endif /* !CONFIG_SRCU */ +static bool device_is_ancestor(struct device *dev, struct device *target) +{ + while (target->parent) { + target = target->parent; + if (dev == target) + return true; + } + return false; +} + /** * device_is_dependent - Check if one device depends on another one * @dev: Device to check dependencies for. @@ -221,7 +231,12 @@ int device_is_dependent(struct device *d struct device_link *link; int ret; - if (dev == target) + /* + * The "ancestors" check is needed to catch the case when the target + * device has not been completely initialized yet and it is still + * missing from the list of children of its parent device. + */ + if (dev == target || device_is_ancestor(dev, target)) return 1; ret = device_for_each_child(dev, target, device_is_dependent);