From mboxrd@z Thu Jan 1 00:00:00 1970 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=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 6093CC433F5 for ; Wed, 15 Sep 2021 08:12:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 498E2608FB for ; Wed, 15 Sep 2021 08:12:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237124AbhIOIN1 (ORCPT ); Wed, 15 Sep 2021 04:13:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56924 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236882AbhIOINM (ORCPT ); Wed, 15 Sep 2021 04:13:12 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9D42C0613EE for ; Wed, 15 Sep 2021 01:11:46 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 83-20020a251956000000b0059948f541cbso2628343ybz.7 for ; Wed, 15 Sep 2021 01:11:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=WuAb6MBtSzivvvxQ/9C3pYrE2NS/OY1FoVAPECcMVH8=; b=K9Yt53VW22oqgQL+/rMGeYCH6nAlDx+0sOi3uZ6egzz66Ue1dohvyJJVcpfqKb9MYT juYS7Kyo38+lI7/M1iZ0Z4LP1zO/geJkWdmbjD+VW46+r72EWzdWXBBjv6lwUPpwVOLJ RKWsGAW/YqC9HI2ozQ1evL2equN9q9opQg87fjJ1w12AJHd3SeeNoSWY3xTcAF3iCPc3 7dMTUMxxWAs0XGTMOqf7mzVoy4VO8rAgkUmbhH7W4fbEoBAz+uanJZUcidlE8FgcVkQh F1Ce0/hd6ycGUBSU+woVOxO9EyU6qcaYuMYcMbN0CeJ4TKjsBOuHQ6WAbs15fhFdbdLx phAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=WuAb6MBtSzivvvxQ/9C3pYrE2NS/OY1FoVAPECcMVH8=; b=VpH1sfrSC7vYxdfjfWglZnS66AkD0ziHt2H7M7lzQ025JT8oBDmt5btDEFpAj4xvXC SI2fjLDvg9QlUL5y2xBOyjH2wLFHbEYuTB+hjmk2uD1C9yA96iuaDbdN2ENONTvhQaN9 X+bvcbAk52Rwy4apFoU5XAU2dhiJSn9XLuDNqBqlxtTQBRYTVn9MQiJavrav2UfVAr5s WRc2rBs5zPRh7hDovGTK9lmOeOdqQl4YS3Ce6imJFY+VyfvOYJrchbMXpKyj/KgBkt5m kPkm7niGaeVncR3aTtNUrCezRRfl6u6GccP1AtX3w88uO1CMwr/5pNdtsZFoqyaHFpsE 1eBg== X-Gm-Message-State: AOAM531qm0qVZD8maulWPz4WUK0YxlUCT/GYuXvlxzzsmHBXaYtfPsQh drb4o+1E60om9G5nQpQxo2AOdQiCWuvYMcw= X-Google-Smtp-Source: ABdhPJzpQv0MpGydkOw27weKviy+9CiEfXH7nqPp8EFl39Q7uzmFnDgg1XrIHMmEKRbkXD/TsDULRd1KM9blN14= X-Received: from saravanak.san.corp.google.com ([2620:15c:2d:3:16d1:ab0e:fc4a:b9b1]) (user=saravanak job=sendgmr) by 2002:a25:1b89:: with SMTP id b131mr4526177ybb.40.1631693506005; Wed, 15 Sep 2021 01:11:46 -0700 (PDT) Date: Wed, 15 Sep 2021 01:11:33 -0700 In-Reply-To: <20210915081139.480263-1-saravanak@google.com> Message-Id: <20210915081139.480263-2-saravanak@google.com> Mime-Version: 1.0 References: <20210915081139.480263-1-saravanak@google.com> X-Mailer: git-send-email 2.33.0.309.g3052b89438-goog Subject: [PATCH v2 1/6] driver core: fw_devlink: Improve handling of cyclic dependencies From: Saravana Kannan To: Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Lunn , Heiner Kallweit , Russell King , "David S. Miller" , Jakub Kicinski , Len Brown , Saravana Kannan Cc: John Stultz , Marek Szyprowski , Rob Herring , Geert Uytterhoeven , Vladimir Oltean , kernel-team@android.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-acpi@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When we have a dependency of the form: Device-A -> Device-C Device-B Device-C -> Device-B Where, * Indentation denotes "child of" parent in previous line. * X -> Y denotes X is consumer of Y based on firmware (Eg: DT). We have cyclic dependency: device-A -> device-C -> device-B -> device-A fw_devlink current treats device-C -> device-B dependency as an invalid dependency and doesn't enforce it but leaves the rest of the dependencies as is. While the current behavior is necessary, it is not sufficient if the false dependency in this example is actually device-A -> device-C. When this is the case, device-C will correctly probe defer waiting for device-B to be added, but device-A will be incorrectly probe deferred by fw_devlink waiting on device-C to probe successfully. Due to this, none of the devices in the cycle will end up probing. To fix this, we need to go relax all the dependencies in the cycle like we already do in the other instances where fw_devlink detects cycles. A real world example of this was reported[1] and analyzed[2]. [1] - https://lore.kernel.org/lkml/0a2c4106-7f48-2bb5-048e-8c001a7c3fda@samsung.com/ [2] - https://lore.kernel.org/lkml/CAGETcx8peaew90SWiux=TyvuGgvTQOmO4BFALz7aj0Za5QdNFQ@mail.gmail.com/ Fixes: f9aa460672c9 ("driver core: Refactor fw_devlink feature") Reported-by: Marek Szyprowski Signed-off-by: Saravana Kannan --- drivers/base/core.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index e65dd803a453..316df6027093 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1772,14 +1772,21 @@ static int fw_devlink_create_devlink(struct device *con, * be broken by applying logic. Check for these types of cycles and * break them so that devices in the cycle probe properly. * - * If the supplier's parent is dependent on the consumer, then - * the consumer-supplier dependency is a false dependency. So, - * treat it as an invalid link. + * If the supplier's parent is dependent on the consumer, then the + * consumer and supplier have a cyclic dependency. Since fw_devlink + * can't tell which of the inferred dependencies are incorrect, don't + * enforce probe ordering between any of the devices in this cyclic + * dependency. Do this by relaxing all the fw_devlink device links in + * this cycle and by treating the fwnode link between the consumer and + * the supplier as an invalid dependency. */ sup_dev = fwnode_get_next_parent_dev(sup_handle); if (sup_dev && device_is_dependent(con, sup_dev)) { - dev_dbg(con, "Not linking to %pfwP - False link\n", - sup_handle); + dev_info(con, "Fixing up cyclic dependency with %pfwP (%s)\n", + sup_handle, dev_name(sup_dev)); + device_links_write_lock(); + fw_devlink_relax_cycle(con, sup_dev); + device_links_write_unlock(); ret = -EINVAL; } else { /* -- 2.33.0.309.g3052b89438-goog