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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 9054FC0650F for ; Thu, 8 Aug 2019 13:05:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AC032171F for ; Thu, 8 Aug 2019 13:05:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="UsXVcz/0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732919AbfHHNF2 (ORCPT ); Thu, 8 Aug 2019 09:05:28 -0400 Received: from mail-qt1-f193.google.com ([209.85.160.193]:36996 "EHLO mail-qt1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732885AbfHHNF1 (ORCPT ); Thu, 8 Aug 2019 09:05:27 -0400 Received: by mail-qt1-f193.google.com with SMTP id y26so92037345qto.4 for ; Thu, 08 Aug 2019 06:05:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=9m6QChW1Hz/Ce2TOg5A9I+Mvna5Z6uz7U57CNrS3DMc=; b=UsXVcz/0fx+mbrQVrDfthdHqx/TQAG6mZCOjIrVyOeqqQ52UZpnPAoCRoyaHnv8XhS myAYX36Qc07br0W255vMKbULw2ztt1SK9LCxY6t+qNSGUH8lgf/3KrkhNmVLhnuXPk75 8NKhNYfOP0paEoLotKXkfyPj6WC9fRZDjL/390dyyF/8bhzq6seIlrIR7AftrabVSUCt 9CsyV03odYVVSHvklvyseXwr4U05s7IrXQRwta90NNKp3g9VPyivRSNNHC+ZMXAvgadj C7aT5FJ9sAlB+caYQhcUKnsovzehTBq/uSqC2bLHwecFVaJ/O/Uv9sooTvOk7mSYFNNc 0qyQ== 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:content-transfer-encoding :in-reply-to:user-agent; bh=9m6QChW1Hz/Ce2TOg5A9I+Mvna5Z6uz7U57CNrS3DMc=; b=ekkGLH/Qhi32zxjbv+vP4HHxYC2y4rgtJ+rBmVKrI5N5GKSLX9yJReMveoZe+NA60u BdYIL40xFODBY5i/cv0+NqIQ/rLvfEw4z0p2qoL+jNEtrSw0iIe8hbjDMjM5MqghPrYD fxxEbcGdZ7HLze3/Ur0CpwxtMmt/7vnCWYPv/Vw1k2PMoS1dOhcvluUntVStGDNp4Fqf AFn1A90V6hqGcddY9xzjc/QBiE0Drw1Q1LKGC2ViAeglkX29HevmwRdg1hb2ukPQxSxn pqM51QwdOXSe0UFqb6D78C0c88kK9BOyiJLNnI+hyD1bea4jVu2i/GCcgWwfyT3HzNnM fHdQ== X-Gm-Message-State: APjAAAU1x4Itvj7zeyYCukDN8s0Itiq8JtzJajGYUtW0TAOltlgQiruP YC3/cEA79xGCESoRXuinnHLb7hpV0X4= X-Google-Smtp-Source: APXvYqxk+1+rmZi904v8k29c8RjsPTgNO19TH+tlNz6F8hGZWv6LBYxggtUeflQkroZ7XbRUiUsHTA== X-Received: by 2002:aed:3ed8:: with SMTP id o24mr12601256qtf.252.1565269526793; Thu, 08 Aug 2019 06:05:26 -0700 (PDT) Received: from ziepe.ca (hlfxns017vw-156-34-55-100.dhcp-dynamic.fibreop.ns.bellaliant.net. [156.34.55.100]) by smtp.gmail.com with ESMTPSA id b1sm15328088qkk.8.2019.08.08.06.05.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 08 Aug 2019 06:05:26 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hvi6f-0003Ih-LV; Thu, 08 Aug 2019 10:05:25 -0300 Date: Thu, 8 Aug 2019 10:05:25 -0300 From: Jason Gunthorpe To: Jason Wang Cc: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH V4 7/9] vhost: do not use RCU to synchronize MMU notifier with worker Message-ID: <20190808130525.GA1989@ziepe.ca> References: <20190807070617.23716-1-jasowang@redhat.com> <20190807070617.23716-8-jasowang@redhat.com> <20190807120738.GB1557@ziepe.ca> <1000f8a3-19a9-0383-61e5-ba08ddc9fcba@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1000f8a3-19a9-0383-61e5-ba08ddc9fcba@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Aug 08, 2019 at 08:54:54PM +0800, Jason Wang wrote: > I don't have any objection to convert  to spinlock() but just want to > know if any case that the above smp_mb() + counter looks good to you? This email is horribly mangled, but I don't think mixing smb_mb() and smp_load_acquire() would be considerd a best-practice, and using smp_store_release() instead would be the wrong barrier. spinlock does seem to be the only existing locking primitive that does what is needed here. Jason