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,URIBL_BLOCKED,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 08E9AC352A2 for ; Wed, 5 Feb 2020 22:34:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D233D2072B for ; Wed, 5 Feb 2020 22:34:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="QaYncY22" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727473AbgBEWeS (ORCPT ); Wed, 5 Feb 2020 17:34:18 -0500 Received: from mail-pg1-f193.google.com ([209.85.215.193]:45049 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727116AbgBEWeR (ORCPT ); Wed, 5 Feb 2020 17:34:17 -0500 Received: by mail-pg1-f193.google.com with SMTP id g3so1648424pgs.11 for ; Wed, 05 Feb 2020 14:34:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=BJAZ+tjDZGEWKOLhDN5AGrWH1BdqO7gaMNKY2ZpYEZE=; b=QaYncY22KA1veHmJfyF9ObQNUPiSi3a+CYQ/HWRhROmmrwOgTOH5jglHbNzKa3crqZ 0yWquqQt2uqdYLCLXrJPtB1A+OFdkF7HpKyn/NN7xtUqFHK7ipFabry5qlMjt0gX01gE iB3UJDUvBVIWfSXh0lUgCf+hLlzcJkZDwHd/4= 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:in-reply-to:user-agent; bh=BJAZ+tjDZGEWKOLhDN5AGrWH1BdqO7gaMNKY2ZpYEZE=; b=P97TlfEr+H/MBdx/rzAOYR6Tb4vwgMRUwdHM/dNq70m7y3vgfRgj/bIL/jN1HNa9xk o21SRNNHC3wQ1SkKcehQd1QkCa/A52i7ek+4lW5pMQu2bwfNRtwm5JMZOZVWKXoSEB8G me48lLAY17NYp5s8l9VKB/gAKQQ7gYsflpt60edAs3Em3deJ5HZoGGvtpdBlAx13CSaG d+j90Lb/leWAxtVRh3Z9dlX+sNXyhP+L7UHVuDahnlPHmYe3TQdIyBVpcwOcXNDt1BwB XBbaYOtVUPEkanMQGmHX3rsH0dTp3iL62ey0FUzkRqMqFAk5gE0Ax3mAt8iuMmlwdpNT HCVQ== X-Gm-Message-State: APjAAAUDV0545VWntXhDnSWntVcPnxEv2Ht2AK4SpIhJVHD/SKNH0mFw GNYFzkbpJB/BR2TvJeWIX2bwwg== X-Google-Smtp-Source: APXvYqwH/JozABknbiZDhGi/qjztmZyyCX4nXbvdvUmqzc6dhXb1KJ7OGhn2QUC6bDzXn1X7tfRLFg== X-Received: by 2002:a63:d0c:: with SMTP id c12mr130039pgl.173.1580942057139; Wed, 05 Feb 2020 14:34:17 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id t19sm784459pgg.23.2020.02.05.14.34.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2020 14:34:16 -0800 (PST) Date: Wed, 5 Feb 2020 17:34:15 -0500 From: Joel Fernandes To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , paulmck@kernel.org, frextrite@gmail.com, rcu@vger.kernel.org, madhuparnabhowmik04@gmail.com Subject: Re: [PATCH] kernel/trace: Use rcu_assign_pointer() for setting fgraph hash pointers Message-ID: <20200205223415.GA55522@google.com> References: <20200205221808.54576-1-joel@joelfernandes.org> <20200205172529.4282a0d1@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205172529.4282a0d1@oasis.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 05, 2020 at 05:25:29PM -0500, Steven Rostedt wrote: > On Wed, 5 Feb 2020 17:18:08 -0500 > "Joel Fernandes (Google)" wrote: > > > set_ftrace_early_graph() sets pointers without any explicit > > release-barriers. Let us use rcu_assign_pointer() to ensure the same. > > > > Note that ftrace_early_graph() calls ftrace_graph_set_hash() which does > > do mutex_unlock(&ftrace_lock); which should imply a release barrier. > > However it is better to not depend on it and just use > > rcu_assign_pointer() which should also avoid sparse errors in the > > future. > > This is going to have to wait for the next merge window, as I'm already > *very* late, and I've pushed the limit to what I will add at this time > frame. I understand, no problem. I will resend it next merge window. thanks, - Joel > > -- Steve >