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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 74D8EC4321B for ; Sun, 28 Apr 2019 23:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 421962067D for ; Sun, 28 Apr 2019 23:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726700AbfD1XTL (ORCPT ); Sun, 28 Apr 2019 19:19:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726393AbfD1XTK (ORCPT ); Sun, 28 Apr 2019 19:19:10 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 624123082B21; Sun, 28 Apr 2019 23:19:10 +0000 (UTC) Received: from llong.remote.csb (ovpn-120-22.rdu2.redhat.com [10.10.120.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0E49C5D9CA; Sun, 28 Apr 2019 23:19:08 +0000 (UTC) Subject: Re: [PATCH-tip v7 00/20] locking/rwsem: Rwsem rearchitecture part 2 From: Waiman Long To: Linus Torvalds Cc: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Linux List Kernel Mailing , the arch/x86 maintainers , Davidlohr Bueso , Tim Chen , huang ying References: <20190428212557.13482-1-longman@redhat.com> <3f8fd44d-1962-e309-49b5-bb16fd662312@redhat.com> Organization: Red Hat Message-ID: <553acf73-e2c4-b094-e088-d53cc7ab9239@redhat.com> Date: Sun, 28 Apr 2019 19:19:08 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <3f8fd44d-1962-e309-49b5-bb16fd662312@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Sun, 28 Apr 2019 23:19:10 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/28/19 7:12 PM, Waiman Long wrote: > On 4/28/19 6:46 PM, Linus Torvalds wrote: >> This doesn't seem to be the full diff - looking at that patch 1 you >> seem to have taken my suggested list_cut_before() change too. >> >> I'm not against it (it does seem to be simpler and better), I just >> hope you double-checked it, since I kind of hand-waved it. >> >> Linus > I implemented your suggestion in patch 1 as it will produce simpler and > faster code. However, one of the changes in my patchset is to wake up > all the readers in the wait list. This means I have to jump over the > writers and wake up the readers behind them as well. See patch 11 for > details. As a result, I have to revert back to use list_add_tail() and > list_for_each_entry_safe() for the first pass. That is why the diff for > the whole patchset is just the below change. It is done on purpose, not > an omission. That is also the reason why it was implemented this way in my v6 patchset. I implemented the fix on top of the rwsem patchset first and then move it backward to the beginning of the patchset for easier backport. Cheers, Longman