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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 906C7C3A5A7 for ; Wed, 4 Sep 2019 11:39:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6FDEB22DBF for ; Wed, 4 Sep 2019 11:39:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728961AbfIDLjX (ORCPT ); Wed, 4 Sep 2019 07:39:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:53510 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727083AbfIDLjX (ORCPT ); Wed, 4 Sep 2019 07:39:23 -0400 Received: from oasis.local.home (bl11-233-114.dsl.telepac.pt [85.244.233.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1A9BB20820; Wed, 4 Sep 2019 11:39:20 +0000 (UTC) Date: Wed, 4 Sep 2019 07:39:15 -0400 From: Steven Rostedt To: Viktor Rosendahl Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Joel Fernandes , Peter Zijlstra Subject: Re: [PATCH v5 1/4] ftrace: Implement fs notification for tracing_max_latency Message-ID: <20190904073915.4a145a91@oasis.local.home> In-Reply-To: <20190903132602.3440-2-viktor.rosendahl@gmail.com> References: <20190903132602.3440-1-viktor.rosendahl@gmail.com> <20190903132602.3440-2-viktor.rosendahl@gmail.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 3 Sep 2019 15:25:59 +0200 Viktor Rosendahl wrote: > +void latency_fsnotify_stop(void) > +{ > + /* Make sure all CPUs see caller's previous actions to stop tracer */ > + smp_wmb(); These memory barriers just look wrong. What exactly are you trying to protect here? Where's the matching rmbs? -- Steve > + static_branch_disable(&latency_notify_key); > + latency_fsnotify_process(); > +} > + > +void latency_fsnotify_start(void) > +{ > + static_branch_enable(&latency_notify_key); > + /* Make sure all CPUs see key value before caller continue */ > + smp_wmb(); > +} > +