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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 EF4D7C33CB1 for ; Wed, 15 Jan 2020 15:04:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5FD024671 for ; Wed, 15 Jan 2020 15:04:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579100675; bh=CY8+8/uxQsF1OKykHvcwrx0bgmlhhQc3BOJbtgvMG/A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=bIUzpYHcMDyk5gXd6/hzvU8LGIq6+z1jIf5wzRoFhwLBE4iDYizBbFjaZpzrhgBJB nilAlOn3Lh6U/hBH7ZXG/9bMxbthoi1WSB7JbOstyjgY3XwP5X07AukRGbCmVo63+t UXFW7BNO6i3x4WYChMvlF3GklIhPqIt4tEO4C1Xw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729221AbgAOPEc (ORCPT ); Wed, 15 Jan 2020 10:04:32 -0500 Received: from mail-wm1-f68.google.com ([209.85.128.68]:38577 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729011AbgAOPEc (ORCPT ); Wed, 15 Jan 2020 10:04:32 -0500 Received: by mail-wm1-f68.google.com with SMTP id u2so200942wmc.3; Wed, 15 Jan 2020 07:04:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=xQvK3Khfh8ssHY6UKXAmXLE4MXakJFMEfTNk2HuT3e8=; b=WGZFfxHNGxkn3qKiGXNyQWIkmR6gZtBOh5T54Ma6DLnAgmyCGoTkrObkQbpbFZqMlO eSfMJg5THDN1axPJZo0QLmYOVFL+9TQ8SVTwzrq9pk6guLbN8wqAi6f6UUvitygc79Uc 0asMaM5hCAG9Ei7rLJ0AGJTO4M1OvvpNbe7+d5iJHdOQWz/5Hamim+9DcLrDRFD7iXSP lJB2SvafIqMd7nJuDHW0VqJQPK6PkytVDkbhuFh9JofDC9Zj5nq6fq+U3JfdMQzC4kDi gDQhAzaOFkXaTQBsq4v7l9sdWA5/+svsLZd8FKdxvtashccRiMYZlDjgmyeGTmAqSngR 27Ag== X-Gm-Message-State: APjAAAU7OxYUn+YDvFqMamo+fti/c3MbPHgVE12IHE7i3KxDHm7S9r4j jRWZ08J5I0pWwGng9XlVJ8I= X-Google-Smtp-Source: APXvYqy279tPnlZqttod0cBi9Mva6wkZHlFzeLjXHeZe9tBQL0b+hXbPpd8U2Ldc2U+oX97PYuyAOw== X-Received: by 2002:a1c:2187:: with SMTP id h129mr244143wmh.44.1579100669759; Wed, 15 Jan 2020 07:04:29 -0800 (PST) Received: from debian (41.142.6.51.dyn.plus.net. [51.6.142.41]) by smtp.gmail.com with ESMTPSA id b137sm133936wme.26.2020.01.15.07.04.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2020 07:04:28 -0800 (PST) Date: Wed, 15 Jan 2020 15:04:26 +0000 From: Wei Liu To: Madhuparna Bhowmik Cc: Wei Liu , paul@xen.org, davem@davemloft.net, xen-devel@lists.xenproject.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E. McKenney" , Joel Fernandes , Amol Grover , linux-kernel-mentees@lists.linuxfoundation.org Subject: Re: [PATCH] net: xen-netbank: hash.c: Use built-in RCU list checking Message-ID: <20200115150426.svapzpux2tbbgvmn@debian> References: <20200115124129.5684-1-madhuparnabhowmik04@gmail.com> <20200115135631.edr2nrfkycppxcku@debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jan 15, 2020 at 07:36:38PM +0530, Madhuparna Bhowmik wrote: [...] > > > The surrounding code makes it pretty clear that the lock is already held > > by the time list_for_each_entry_rcu is called, yet the checking involved > > in lockdep_is_held is not trivial, so I'm afraid I don't consider this a > > strict improvement over the existing code. > > > > Actually, we want to make CONFIG_PROVE_LIST_RCU enabled by default. I think you meant CONFIG_PROVE_RCU_LIST. > And if the cond argument is not passed when the usage of > list_for_each_entry_rcu() > is outside of rcu_read_lock(), it will lead to a false positive. > Therefore, I think this patch is required. Fair enough. Wei.