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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 DAB9FC43441 for ; Wed, 21 Nov 2018 22:41:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A114E206B2 for ; Wed, 21 Nov 2018 22:41:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amarulasolutions.com header.i=@amarulasolutions.com header.b="LHaqXnBP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A114E206B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=amarulasolutions.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390250AbeKVJRx (ORCPT ); Thu, 22 Nov 2018 04:17:53 -0500 Received: from mail-ed1-f50.google.com ([209.85.208.50]:45506 "EHLO mail-ed1-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387465AbeKVJRx (ORCPT ); Thu, 22 Nov 2018 04:17:53 -0500 Received: by mail-ed1-f50.google.com with SMTP id d39so6139705edb.12 for ; Wed, 21 Nov 2018 14:41:28 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amarulasolutions.com; s=google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=iyu+r1qU4x4WLB9qIma9AHESoTIw5m2Vat5BZdT61Oo=; b=LHaqXnBP/y8+l+vQOkAC9X0L09mU85qyc+TDzjjunQCm2KJVcyB4Gw5eTF2LN9Muuj KtghmKz5NGhop25VwimTWbRsuiwEi0K62jCj1AmkY0bnEzRS9/7O1vol0jE1g2ReoT/8 bIyqy9cEP6PGZ5DgOujno5xQaO2/sxjF/zmAk= 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:mime-version :content-disposition:user-agent; bh=iyu+r1qU4x4WLB9qIma9AHESoTIw5m2Vat5BZdT61Oo=; b=Qd3e9bgKe914pntXVNfvBAtPC8GA42gZKuN7HvyDk+Q9k3FGBdb5vQpPaubyugDfYc FdQ0Zp5cfM3fJMnXVshIZA5E8MbupLEvMcjGE/UuWrS75QWk3Ax+xxsSocoqAyQV7RdO NkKBmXz/KgJtbSt0nWoZIqKxNJIBGduKPYq9+DYnRncuZBmHJTkYWDRK4yW5H7vuSeHk DjIBNhWO4En3u5Y9EVnBBHBwRZRE6x1xNb6z6mtyRr6x8iHxpNQL1JSbXELZm85vzyYR Qs+wN2A1eIEGzZddmhW5Xy8ohqo+6pvxBnmuI1X2cVrUG4y2eO+1vtgGG/Hwe81k2LPN H5pA== X-Gm-Message-State: AA+aEWZWkvKwXFjJn2t/dC12VN6QZbr14OmAxT59ViMF+4RJdTH9k97A 9Rzb3ZdlSd88ew4ZSMau6OCmEA== X-Google-Smtp-Source: AFSGD/Ww0EH1zrGj/4fAFvcSJL/Q810COOxA8wVf4lVD6mpU/+OXbvA24r1gdssPQ73DAheG8HhBsg== X-Received: by 2002:a50:ad97:: with SMTP id a23mr6814441edd.128.1542840087676; Wed, 21 Nov 2018 14:41:27 -0800 (PST) Received: from andrea (dynamic-2a00-1028-8386-da8a-eacb-c188-78b9-634c.ipv6.broadband.iol.cz. [2a00:1028:8386:da8a:eacb:c188:78b9:634c]) by smtp.gmail.com with ESMTPSA id a22-v6sm2917461ejv.17.2018.11.21.14.41.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 21 Nov 2018 14:41:27 -0800 (PST) Date: Wed, 21 Nov 2018 23:41:24 +0100 From: Andrea Parri To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Oleg Nesterov Cc: linux-kernel@vger.kernel.org Subject: [Question] smp_wmb() in prepare_uprobe() Message-ID: <20181121224124.GB4016@andrea> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, The comment for the smp_wmb() in prepare_uprobe() says: "pairs with rmb() in find_active_uprobe()" but I see no (smp_)rmb() in find_active_uprobe(); I see the smp_rmb() in handle_swbp(): is this the intended pairing barrier? Which memory accesses do you want to "order" with this pairing? Thanks, Andrea