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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 A3FBDC63793 for ; Thu, 22 Jul 2021 09:30:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 91CE46121E for ; Thu, 22 Jul 2021 09:30:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231428AbhGVIth (ORCPT ); Thu, 22 Jul 2021 04:49:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231187AbhGVItg (ORCPT ); Thu, 22 Jul 2021 04:49:36 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAE22C061575 for ; Thu, 22 Jul 2021 02:30:11 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id e14so3774978plh.8 for ; Thu, 22 Jul 2021 02:30:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=RSgVdB0+HpET8iLINuWOoeOWDDxUJjmmluxZNEz35KA=; b=o6LJ/myMP6JO8ChH8dYoqq21TZnuVfWqQC7aMNZVbEwvgt/wmupSJe5X7mUycZZ1OP wZUOpxPzR0Di4iK476owf2txOnd8aRvZIuWOSyNSQwF8qAfJx1gZjc1rqQNENDcoU4k8 pWfm16Rm2AyVdjC+e3kTofDMg7W/f1X4eU9NPEhv7mUcvN6ebC/kCdQLgGMJIgNOCd38 Z79Cpgk8vmBkJLmcW9tTTfCW8TJv/6nRrpzuj2HycvK3LMZlVo0xpmCpHif6k1kmeqBf /hzT0Pmizi11dqx4L91lE1OKq6ULDL3w/A5pjP58k83vlOPYfDR9I9UDXt06Iw0JzA4O hv7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=RSgVdB0+HpET8iLINuWOoeOWDDxUJjmmluxZNEz35KA=; b=kbRH1U9nwf1U1DWF7u1bHeefg5kPHvAo3Uvf2cXwAx+Sh0L5x9WRg8Xq5KbutYjtt0 Chv2Iu5+9ZQLx3QcZdIo+WiFlM6z3w8UQAj9mdvVJYJ9wahNIXAWEd8SPdKGfG9Ys+7y 1Tt4xpcHPtI9jtbUo/PkUVkMBLx7cEBFqMhSOVtgSGcFbGYAub/T4+sQ0gHC9uMfsKvj PS+CcOWk59vt51+5ciPyzhUMum2M4SVEHuUUC/wPyuxxVTyk7ExZBQwIh3V83XcUB7yM hCg/WHcLe35WGbf9eg+7cZi3ljPvf+dD3rf+GQK4Tqc8BAi2K3XAg+3FvaU2HcRLNuBE QTYA== X-Gm-Message-State: AOAM532FOpIITt2YX4M5WE7LC4IHFxd+C+TlyJ3/R/aHpuW+zsFbsETH YiQoyr60xnBqhVz5FLiFKDM= X-Google-Smtp-Source: ABdhPJyscK7c550TzHfpDv1WRnYYvoBsSoBWYdMCW0natilUebpT1uRY7os1lbemOjfZnuzWFb0RqA== X-Received: by 2002:a05:6a00:2306:b029:331:ebe8:a4b4 with SMTP id h6-20020a056a002306b0290331ebe8a4b4mr39978184pfh.15.1626946211504; Thu, 22 Jul 2021 02:30:11 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id q5sm1069592pjo.7.2021.07.22.02.30.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jul 2021 02:30:11 -0700 (PDT) From: Desmond Cheong Zhi Xi To: linux-graphics-maintainer@vmware.com, zackr@vmware.com, airlied@linux.ie, daniel@ffwll.ch, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de Cc: Desmond Cheong Zhi Xi , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, Daniel Vetter Subject: [PATCH 1/3] drm: use the lookup lock in drm_is_current_master Date: Thu, 22 Jul 2021 17:29:27 +0800 Message-Id: <20210722092929.244629-2-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210722092929.244629-1-desmondcheongzx@gmail.com> References: <20210722092929.244629-1-desmondcheongzx@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Inside drm_is_current_master, using the outer drm_device.master_mutex to protect reads of drm_file.master makes the function prone to creating lock hierarchy inversions. Instead, we can use the drm_file.master_lookup_lock that sits at the bottom of the lock hierarchy. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi --- drivers/gpu/drm/drm_auth.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index f00354bec3fb..9c24b8cc8e36 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -63,8 +63,9 @@ static bool drm_is_current_master_locked(struct drm_file *fpriv) { - lockdep_assert_held_once(&fpriv->minor->dev->master_mutex); - + /* Either drm_device.master_mutex or drm_file.master_lookup_lock + * should be held here. + */ return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; } @@ -82,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv) { bool ret; - mutex_lock(&fpriv->minor->dev->master_mutex); + spin_lock(&fpriv->master_lookup_lock); ret = drm_is_current_master_locked(fpriv); - mutex_unlock(&fpriv->minor->dev->master_mutex); + spin_unlock(&fpriv->master_lookup_lock); return ret; } -- 2.25.1