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=-12.8 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 D20C2C433E6 for ; Tue, 1 Sep 2020 18:44:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4A942078B for ; Tue, 1 Sep 2020 18:44:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=google.com header.i=@google.com header.b="g0AbURRG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730652AbgIASow (ORCPT ); Tue, 1 Sep 2020 14:44:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726102AbgIASou (ORCPT ); Tue, 1 Sep 2020 14:44:50 -0400 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42665C061244 for ; Tue, 1 Sep 2020 11:44:50 -0700 (PDT) Received: by mail-qv1-xf49.google.com with SMTP id l29so1655528qve.18 for ; Tue, 01 Sep 2020 11:44:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=lzhpqq8bzD/FsaCTfkvt8bsW4hhopaei7M9mtOQ3b7A=; b=g0AbURRGuByGLoi+yDQWo3qk5VT8Y8gTd1nXll8yg8pR3A+kjAmWplpHcfk0+zOGIo KsLMPMVlxScwnCLKfSMCqdWD8+iX8p/onFM8QmcSZH6utZKed3sd+z7uBRmLahFsIjj/ MlTzqniO6cUe9Q3GS8H7BAbdlCo+tqw4EiHXiSbagNyyxRS9yH615tjjaORSHXIYP2LV VMoJMegISpjs4KPE7XAnCybNiFW/D/Wr4LYRQHqZm1we9HhO0xLOBXT3v5oP7mT9O8/U VJ/CprcRHopb0GP1Ftlf0jI3ZEdfiHhgTWpv+Vf1hlhQvH/aE0Kz+C5pp16/DqKIpohL YmBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=lzhpqq8bzD/FsaCTfkvt8bsW4hhopaei7M9mtOQ3b7A=; b=FuEWidKiv1/1VBQRi+UA3hjaHDJytGIbRyQv2kCiacbhLU6S7vlalCa+GNNj/2Qeb0 +DTfuxKh3ZQRLuzDAVT6M/kIl3d8DviAxnbg8ZQIe/lris0axuU709M+6P3JeTwV2y3Y 7nanIb2jX/G8VJmwAwpfxCRF5vBOCBA+Tb5C2u1nKSz5MLfjpfmA/DDZ2I074mGHURnW ckir/ppKB22APlu/9ZPdj2d9n/i9cJeLWZKu5sLQHN/qHKcwPhVNy10sWTXYiv4kxS3s kisU9LI3wqq0KScH0YEQuhIU1zNdclY3AL35Wu0VXu5buCHN1XyX7D55KLDWL0UWMLze Gqvw== X-Gm-Message-State: AOAM532u9STylfKD3F7OoYRuH7YXvWnN/XjH67Mvsjjx3i8F+YLHNdHD Kv0s6z2bRs2AI8IWzI0JQdAhgsEBEWVO4Jc= X-Google-Smtp-Source: ABdhPJzh8gaRFmSXXD1HZfckYU1uQH2CHBg2Z8WbzU3UOWT8yr6hfKlXtXxkxUNQSHLtC6QtkJxinFdWAK4L6OQ= X-Received: from saravanak.san.corp.google.com ([2620:15c:2d:11:7220:84ff:fe09:fedc]) (user=saravanak job=sendgmr) by 2002:a0c:9b89:: with SMTP id o9mr3313403qve.77.1598985889330; Tue, 01 Sep 2020 11:44:49 -0700 (PDT) Date: Tue, 1 Sep 2020 11:44:44 -0700 Message-Id: <20200901184445.1736658-1-saravanak@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.402.g5ffc5be6b7-goog Subject: [PATCH v2] driver core: Fix device_pm_lock() locking for device links From: Saravana Kannan To: Greg Kroah-Hartman , "Rafael J. Wysocki" , Saravana Kannan Cc: linux-imx@nxp.com, linux-arm-kernel@lists.infradead.org, Dong Aisheng , Shawn Guo , Sascha Hauer , linux@roeck-us.net, m.szyprowski@samsung.com, naresh.kamboju@linaro.org, Peng Fan , Stephen Boyd , Dong Aisheng , kernel-team@android.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit fixes two issues: 1. The lockdep warning reported by Dong Aisheng [1]. It is a warning about a cycle (dpm_list_mtx --> kn->active#3 --> fw_lock) that was introduced when device-link devices were added to expose device link information in sysfs. The patch that "introduced" this cycle can't be reverted because it's fixes a real SRCU issue and also ensures that the device-link device is deleted as soon as the device-link is deleted. This is important to avoid sysfs name collisions if the device-link is create again immediately (this can happen a lot with deferred probing). 2. Inconsistency in grabbing device_pm_lock() during device link deletion Some device link deletion code paths grab device_pm_lock(), while others don't. The device_pm_lock() is grabbed during device_link_add() because it checks if the supplier is in the dpm_list and also reorders the dpm_list. However, when a device link is deleted, it does not do either of those and therefore device_pm_lock() is not necessary. Dropping the device_pm_lock() in all the device link deletion paths removes the inconsistency in locking. Thanks to Stephen Boyd for helping me understand the lockdep splat. Fixes: 843e600b8a2b ("driver core: Fix sleeping in invalid context during device link deletion") [1] - https://lore.kernel.org/lkml/CAA+hA=S4eAreb7vo69LAXSk2t5=DEKNxHaiY1wSpk4xTp9urLg@mail.gmail.com/ Reported-by: Dong Aisheng Signed-off-by: Saravana Kannan --- Cc'ing everyone from the original thread [1] -Saravana drivers/base/core.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index f6f620aa9408..07e5ceb40bb1 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -807,9 +807,7 @@ static void device_link_put_kref(struct device_link *link) void device_link_del(struct device_link *link) { device_links_write_lock(); - device_pm_lock(); device_link_put_kref(link); - device_pm_unlock(); device_links_write_unlock(); } EXPORT_SYMBOL_GPL(device_link_del); @@ -830,7 +828,6 @@ void device_link_remove(void *consumer, struct device *supplier) return; device_links_write_lock(); - device_pm_lock(); list_for_each_entry(link, &supplier->links.consumers, s_node) { if (link->consumer == consumer) { @@ -839,7 +836,6 @@ void device_link_remove(void *consumer, struct device *supplier) } } - device_pm_unlock(); device_links_write_unlock(); } EXPORT_SYMBOL_GPL(device_link_remove); -- 2.28.0.402.g5ffc5be6b7-goog