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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C5AA5C43334 for ; Thu, 21 Jul 2022 12:08:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233436AbiGUMIx (ORCPT ); Thu, 21 Jul 2022 08:08:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232830AbiGUMIw (ORCPT ); Thu, 21 Jul 2022 08:08:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDC6B85F95; Thu, 21 Jul 2022 05:08:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 76A0A61CFF; Thu, 21 Jul 2022 12:08:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 22D1FC3411E; Thu, 21 Jul 2022 12:08:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658405330; bh=LXie3sbnk8wgU9gzwq8ntIR3HYeqzQkMMgEXBK+44jE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fipYXFe5tkugtJrcKyXxa51hr12B18OxkCCuzLPicXgcFU20MBvpER5VMZsrll6nS bE8UKSXOLSkCbjARk7NzKSVcLyWkyrSseoI3t3bkI7JqVziq+qyjIP/juaJRuub3Tf VMhNkMUHeBXvBNGGC/rJuA6xQak+5eHNrJD1qP9++LypHnACsuCIefculn2UafC/KO l1RJjkiz/gBrNBlZgiDcHnVTuEMiXElL4mZ/G3kDz93QU66JsHxnnRm3+SiKyn8nhQ 5RdyVlwiIpJgzpsuEMRKuQSyfQ9UfunsyPlob3N8oDajqgSMPV/oqtNrMsEb+PaKHJ PkFglKMtlfOUg== Message-ID: <3c0a4cb5-f88f-ec5f-e614-d1e8ceb036c2@kernel.org> Date: Thu, 21 Jul 2022 14:08:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH V6 04/16] rv/include: Add deterministic automata monitor definition via C macros Content-Language: en-US To: Steven Rostedt Cc: Wim Van Sebroeck , Guenter Roeck , Jonathan Corbet , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Will Deacon , Catalin Marinas , Marco Elver , Dmitry Vyukov , "Paul E. McKenney" , Shuah Khan , Gabriele Paoloni , Juri Lelli , Clark Williams , Tao Zhou , Randy Dunlap , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-devel@vger.kernel.org References: <9ffc05b67fff087413143a420373731e0e34eef4.1658244826.git.bristot@kernel.org> <20220720160606.3e672b55@gandalf.local.home> From: Daniel Bristot de Oliveira In-Reply-To: <20220720160606.3e672b55@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On 7/20/22 22:06, Steven Rostedt wrote: >> +/* \ >> + * da_monitor_enabled_##name - checks if the monitor is enabled \ >> + */ \ >> +static inline bool da_monitor_enabled_##name(void) \ >> +{ \ > Should we add a: > > smp_rmb(); > > here? And then a smp_wmb() where these switches get updated? > Makes sense. Should I also add the READ_ONCE/WRITE_ONCE? like smp_rmb() READ_ONCE(var) WRITE_ONCE(var, value) smp_wmb() for all these on/off knobs, or just the barriers? > I guess how critical is it that these turn off immediately after the switch > is flipped? It is not critical to continue the execution of those that have already crossed by the variable. Still, waiting for the tracepoints to finish their execution before returning to the user-space task that disabled the variable might be a good thing. IIRC, we can do that via RCU... like, synchronize_rcu()? >> + /* global switch */ \ >> + if (unlikely(!rv_monitoring_on())) \ >> + return 0; \ >> + \ >> + /* monitor enabled */ \ >> + if (unlikely(!rv_##name.enabled)) \ >> + return 0; \ >> + \ >> + return 1; \ >> +} \ >> + \