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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 96F37C4338F for ; Sun, 25 Jul 2021 10:09:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6916660F36 for ; Sun, 25 Jul 2021 10:09:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230483AbhGYJ2e convert rfc822-to-8bit (ORCPT ); Sun, 25 Jul 2021 05:28:34 -0400 Received: from mout.kundenserver.de ([217.72.192.74]:48749 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230370AbhGYJ2e (ORCPT ); Sun, 25 Jul 2021 05:28:34 -0400 Received: from mail-wm1-f42.google.com ([209.85.128.42]) by mrelayeu.kundenserver.de (mreue107 [213.165.67.113]) with ESMTPSA (Nemesis) id 1Mrggc-1lKBsR3Gtw-00nkfb for ; Sun, 25 Jul 2021 12:09:03 +0200 Received: by mail-wm1-f42.google.com with SMTP id 9-20020a05600c26c9b02901e44e9caa2aso4334895wmv.4 for ; Sun, 25 Jul 2021 03:09:03 -0700 (PDT) X-Gm-Message-State: AOAM532XNr6XG35ebqncDGSWTpdYb6fN0warEt8faWJUDIEz5o4zZUpd /SbpzLbWSw2b9ganahiUe7MfRL/pu1NAhsHTQ30= X-Google-Smtp-Source: ABdhPJwKkuq9IyT9ix9adMAIBJvApSkY0aVFSbpXN2wXNtPNLvh2TJXlAkOVna8U7GvDUui15zMpNgHsagBC8nPgQNU= X-Received: by 2002:a1c:c90f:: with SMTP id f15mr22048881wmb.142.1627207743442; Sun, 25 Jul 2021 03:09:03 -0700 (PDT) MIME-Version: 1.0 References: <20210724123617.3525377-1-chenhuacai@loongson.cn> In-Reply-To: From: Arnd Bergmann Date: Sun, 25 Jul 2021 12:08:47 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH RFC 1/2] arch: Introduce ARCH_HAS_HW_XCHG_SMALL To: Jiaxun Yang Cc: Arnd Bergmann , Huacai Chen , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Guo Ren , linux-arch , Rui Wang , Xuefeng Li , Huacai Chen Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Provags-ID: V03:K1:eHQMSulQF/NycijIbi7tjP/4EhnMZ+PawpSqQvXIh5Z3Olnkzg0 1ffiMLo6uoDGUBXfhbgWzMq8HMRjhVlSzkpI/NVv0Q+wnFEGbySFROdmhOXYCi8oq7Kz834 oryovAT0Gprdq3vnVa5YmycjdHZ6KQt8uvfW8VxKQochzeyb8iYgoYFb5zqimRp3AN5ZSh/ v2O0Qs42y614bTNDCRgww== X-UI-Out-Filterresults: notjunk:1;V03:K0:v1ycOAy8bU0=:hJd4UqfYzXINxCHJo8J4AH k6DY+Till4MvQXz0YRZpW9KzIGTO2u0yR9TMIG5//x2lQ8sOnrxkLj9jY0YuqRqgdWkW+wBqV pVEybVJisU94iLlRlbHhtlXsA+XAwU3IBzTuGGX1CnQ0obRNDrcg+RM6EQD7xttvOsPq3DRnm 0sgX1OD7TzZba8prouh3IS2ImTVmH8NJeFW+cXTq2lWSA+OU0Rx15WQS1K/8QVRuA/pBN+Sim 1XE14906/JL+XjcbqqZ7HkoaY3N9hVm4xgvKBzaEqHblSXJiCa7cat+6g/DxkkNId09syugIA vgDCbqRsmpWJqF60ROr7KIdfthPcOMckTblBf8YFms7ra5w7Bn2XWfXZg9qCObfHAEsM9ZCY9 ZuGmK2otYwBICxzLJiDUNTLziI6be0TxoXEsk1btMsO4AVRSVHzb33JM8Nry9C4ZEzfAdWy/T oO9F2OMXtQhLnAv7WtZGhJ6Sgck4wCxoJkVFZiUe5rJ1NWfZdxnWc2efw++FkPrjvmjsjppd7 ZFE9RqtwHZtfifZ4Wcpb4ZsyedBulN+k+rhRWFDrFu+X4546EKNUTue3XhtWBI3LAsXDgm/5P cgJ5bskasKjio2+57B65s3CPmSgvZ9AP0MpbQmv1xnYberAvt1GIkfW1cAIDtD09glPsSiMPX i4X+R0zqeHjM4gmBoGS0/x5Vh5JK9y9kEgFedZFhMUWePM1GwoiZMe1Flv5X9owJy5Zd+fGoO 6+oofjs8jIhBqpiFC2mXo13LHuAY74I5PCXK15hvfbNb7Cq8Jrujr+ma0TNy2K5zIGY9BkF1x dM9R1EQSw8s7Pcpxwo2rNODtEhVpvcHn6+Z0WljCNdUGyCsV8FVe7VvxfJSZ07pZpymdbv7T+ qMIPDAnJkEE1gOOBQZ3sVQzO/PE1XE5P+5EmlVZcGq+qpMTegg7oH8wXWffI6gTZJIU1pz+IH fjh0K+vj/I7YnAuWX7QhVNoTQMOup7LXujw2ZUbe5TcrJ9mkWgBLa Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Sun, Jul 25, 2021 at 5:06 AM Jiaxun Yang wrote: > 在 2021/7/25 上午3:24, Arnd Bergmann 写道: > > - If I remember correctly, there were some concerns about whether using > > this information for picking the qspinlock implementation is a good idea. > We've checked previous attempt made by Guo Ren about > ARCH_USE_QUEUED_SPINLOCKS_XCHG32[1], the concerns of potential livelock > do exist. > > So in this patch Huacai took another, dropping the whole standalone > tailing logic to remove the usage of sub-word xchg. It could be understood as > partial revert of 69f9cae9 ("locking/qspinlock: Optimize for smaller NR_CPUS") > [2] on these architectures. Ok, I see. Let's see what Peter thinks about it. Arnd