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 097AAC4332F for ; Wed, 30 Nov 2022 15:47:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229786AbiK3Pri (ORCPT ); Wed, 30 Nov 2022 10:47:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229987AbiK3Prh (ORCPT ); Wed, 30 Nov 2022 10:47:37 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E31AF11170; Wed, 30 Nov 2022 07:47:35 -0800 (PST) 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 C65EA617C3; Wed, 30 Nov 2022 15:47:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9687FC433C1; Wed, 30 Nov 2022 15:47:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669823254; bh=Ms6zG9bes1a4dywnpkOvtzh48RrPOPi6LWLATgEHGV0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=g098uW20SxRasYSkI8fyvQx47YyB9NUE3mdEQYw5JBwdboQoEnYgB7mxaHSGyNW+m LaDFTnSeyKqNNRx8+hzTf9BjF4uLiVFb7oX4W3jS3GhFVuxlzWz3y0gjUFYvx12Hcg o4o9C4r+mHR2nLIWw1YVjY/dl0CVMfSf2GtuqvfDzNA/GzCcR7T7FvjGd4f4zuJ0Pv G7KWKje8TNoZ/KUlAHgmXkJVaoKdg2SVq/e41IxMjPuSXRw36QXrhGluzt4rsHxuxB mJBQboNgAb4EDD4h0xIQs2KJnCkVK9HzMkMezecZpoQTlbXliYr18pLibLFsS+1eB3 VmCcRJuRJzE5w== Message-ID: <700e7f91-00a9-d625-741d-122b9b1e1e1c@kernel.org> Date: Wed, 30 Nov 2022 16:47:29 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH V3 2/3] tracing/osnoise: Add preempt/irq disable options Content-Language: en-US To: Steven Rostedt Cc: Masami Hiramatsu , Jonathan Corbet , Juri Lelli , Clark Williams , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <03d4a8522792fa3a51920c79f8a5074933a2fcb3.1669409262.git.bristot@kernel.org> <20221128153919.33c008d1@gandalf.local.home> From: Daniel Bristot de Oliveira In-Reply-To: <20221128153919.33c008d1@gandalf.local.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/28/22 21:39, Steven Rostedt wrote: > On Fri, 25 Nov 2022 22:20:23 +0100 > Daniel Bristot de Oliveira wrote: > >> @@ -1308,6 +1315,8 @@ static void notify_new_max_latency(u64 latency) >> */ >> static int run_osnoise(void) >> { >> + bool preempt_disable = test_bit(OSN_PREEMPT_DISABLE, &osnoise_options); >> + bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options); > > bool irq_disable = test_bit(OSN_IRQ_DISABLE, &osnoise_options); > bool preempt_disable = IS_ENABLED(CONFIG_PREEMPT) && > !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options); Ooops again, that is not exactly what I wanted, because... >> struct osnoise_variables *osn_var = this_cpu_osn_var(); >> u64 start, sample, last_sample; >> u64 last_int_count, int_count; >> @@ -1335,6 +1344,14 @@ static int run_osnoise(void) >> */ >> threshold = tracing_thresh ? : 5000; >> >> + /* >> + * IRQ disable also implies in preempt disable. >> + */ >> + if (irq_disable) >> + local_irq_disable(); > > if (preempt_disable) >> + preempt_disable(); >> + >> /* >> * Make sure NMIs see sampling first >> */ >> @@ -1422,16 +1439,21 @@ static int run_osnoise(void) >> * cond_resched() >> */ >> if (IS_ENABLED(CONFIG_PREEMPT_RCU)) { >> - local_irq_disable(); >> + if (!irq_disable) >> + local_irq_disable(); >> + >> rcu_momentary_dyntick_idle(); >> - local_irq_enable(); >> + >> + if (!irq_disable) >> + local_irq_enable(); >> } >> >> /* >> * For the non-preemptive kernel config: let threads runs, if >> - * they so wish. >> + * they so wish, unless set not do to so. >> */ Then I end up cond_resched'ing here in the non-preemptive kernel. >> - cond_resched(); >> + if (!irq_disable && !preempt_disable) >> + cond_resched(); But I also want to avoid this cond_resched if preempt_disable is set. So, I will merge both things: - change the preempt_disable assignment to check !irq_disabled, like: /* * Disabling preemption is only required if IRQs are enabled, and the options is set on. */ preempt_disable = !irq_disable && test_bit(OSN_PREEMPT_DISABLE, &osnoise_options); - change the preempt disabled if to if (IS_ENABLED(CONFIG_PREEMPT) && preempt_disabled) preempt_disable(); I tested with both preemption models (preemptive and not preemptive) and it works fine. am I missing something? -- Daniel >> last_sample = sample; >> last_int_count = int_count; >> @@ -1450,6 +1472,14 @@ static int run_osnoise(void) >> */ >> barrier(); >> >> + /* >> + * Return to the preemptive state. >> + */ > > if (preempt_disable) >> + preempt_enable(); >> + > >> + if (irq_disable) >> + local_irq_enable(); > > -- Steve > >> /* >> * Save noise info. >> */