Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABC20C05027 for ; Sun, 29 Jan 2023 07:33:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231797AbjA2Hdc (ORCPT ); Sun, 29 Jan 2023 02:33:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232476AbjA2Hda (ORCPT ); Sun, 29 Jan 2023 02:33:30 -0500 Received: from mail-ej1-x629.google.com (mail-ej1-x629.google.com [IPv6:2a00:1450:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8A0DF1C33E for ; Sat, 28 Jan 2023 23:33:29 -0800 (PST) Received: by mail-ej1-x629.google.com with SMTP id bk15so23854018ejb.9 for ; Sat, 28 Jan 2023 23:33:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=6Khnf0tXeS7m38nFYQvDT/lNBrPynSjLK/zhidtRBTI=; b=Lf/xVkaeaMDwt7Zm+kxcMtYJVmn29ApHwgVM7VnG6guuj4kpruR287Bc9XQHGCRT4s bSU786g1S6qyfZRavQmyLBTKUa8OdxXm4koUdbrEMw/rQMYvviXC8ELK1exIHa7ANu7A N/rwegXubp8BVXJaLR2uYkFrSB2/WQ1TWObp0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=6Khnf0tXeS7m38nFYQvDT/lNBrPynSjLK/zhidtRBTI=; b=fDQLH7Dah0Qbx0RDNK80h5idA5/yoJ/sTM45qXeCHdMdRJmJF2WJX5DE9E+yyJIu4b 4VbLV9FkwUCj5etZnZjqntw0fKUhAwOQ01q4T3ly/FcomFZDntKI5OoN2WCa0D/dJTv6 svB7uQefv3DvgC5S5kk5mznzns4KRao+cgnF3veNWIzHsIJQ9C7dah4mvPzScAdjlex0 OuE+fjMCrsiHK1Jss7JMYRTPyKd7ppN6UwH5M16M81Lq3nRD/tRqEHyTHQS7Z7U05dwY ycmKkOHv/OdbAA1pgFR0z9DqN//fiE511Bh8xE+9iAQs79wwx8DnDxxBChavih4WfdDI IdFg== X-Gm-Message-State: AO0yUKV/C8LsXAjV5EWlHvtTjxWXIYfdxpeERDvsMoT3D6jAwD8m1Hn4 rN7BP0HnKtQym98xgWwlF9oac8QawbUVjqOzkSk= X-Google-Smtp-Source: AK7set+/DsRZ46ca45kzZYJo2hYXIoXYt1P5ptFDxPMiAt8IGwDc165CqD2B0D8sKKWP6mQu9s918Q== X-Received: by 2002:a17:906:c20e:b0:885:dd71:89b5 with SMTP id d14-20020a170906c20e00b00885dd7189b5mr2084588ejz.41.1674977606775; Sat, 28 Jan 2023 23:33:26 -0800 (PST) Received: from mail-ej1-f54.google.com (mail-ej1-f54.google.com. [209.85.218.54]) by smtp.gmail.com with ESMTPSA id e13-20020a170906248d00b0087a9f699effsm3934595ejb.173.2023.01.28.23.33.25 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 28 Jan 2023 23:33:25 -0800 (PST) Received: by mail-ej1-f54.google.com with SMTP id p26so12650640ejx.13 for ; Sat, 28 Jan 2023 23:33:25 -0800 (PST) X-Received: by 2002:a17:906:add6:b0:878:51a6:ff35 with SMTP id lb22-20020a170906add600b0087851a6ff35mr3051378ejb.43.1674977604915; Sat, 28 Jan 2023 23:33:24 -0800 (PST) MIME-Version: 1.0 References: <20230129060452.7380-1-zhanghongchen@loongson.cn> In-Reply-To: <20230129060452.7380-1-zhanghongchen@loongson.cn> From: Linus Torvalds Date: Sat, 28 Jan 2023 23:33:08 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4] pipe: use __pipe_{lock,unlock} instead of spinlock To: Hongchen Zhang Cc: Alexander Viro , Andrew Morton , "Christian Brauner (Microsoft)" , Luis Chamberlain , David Howells , Mauro Carvalho Chehab , Eric Dumazet , "Fabio M. De Francesco" , Christophe JAILLET , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, maobibo , Matthew Wilcox , Sedat Dilek Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 28, 2023 at 10:05 PM Hongchen Zhang wrote: > > Use spinlock in pipe_{read,write} cost too much time,IMO > pipe->{head,tail} can be protected by __pipe_{lock,unlock}. > On the other hand, we can use __pipe_{lock,unlock} to protect > the pipe->{head,tail} in pipe_resize_ring and > post_one_notification. No, we really can't. post_one_notification() is called under the RCU lock held, *and* with a spinlock held. It simply cannot do a sleeping lock like __pipe_lock(). So that patch is simply fundamentally buggy, I'm afraid. Linus