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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS 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 6FF23C433E6 for ; Thu, 18 Feb 2021 05:04:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 30EF864E28 for ; Thu, 18 Feb 2021 05:04:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229755AbhBRFD5 (ORCPT ); Thu, 18 Feb 2021 00:03:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:51168 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229460AbhBRFDy (ORCPT ); Thu, 18 Feb 2021 00:03:54 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 92FBC64DA8; Thu, 18 Feb 2021 05:03:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613624593; bh=BiZSHcxv8WWzDhcxoQsCPxk7cnJSi3PjK2CmEvrCw6Y=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=WWUnQt3jhz4DBOiq/9gWeyyHj0wq+gYQiCGvLM7QhwozF2wxr960YniXx4RVUPpnY NkonaOKbPTmJL5t+JjymvZxhlm+WAgsaYGqSY9+bNJR0Pjos5zyJz8K7KloaBkaoEX RoYtAJXDMVVCGa8uVoy6QAtnbsb1Lat18fAf7HsfPaoUvtNjCLjeRyNvNDZbZ6ilGT Q1HKljFmlkkw8aBypwbB9cuXqF9EfkGC6wMFrtniTNPUrmP0aKw0qZYd4BUhrqtbq8 bJoZJLkiD9oDWmi5mzEl9xnCCuXPNiS0ST0shHQ9BAAjTKQirRuOvJpVg/HyvFlwPZ cusTnFCd9mRuA== Date: Thu, 18 Feb 2021 14:03:07 +0900 From: Masami Hiramatsu To: paulmck@kernel.org Cc: Sebastian Andrzej Siewior , Peter Zijlstra , Thomas Gleixner , Uladzislau Rezki , LKML , RCU , Michael Ellerman , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Michal Hocko , "Theodore Y . Ts'o" , Oleksiy Avramchenko , rostedt@goodmis.org Subject: Re: [PATCH 2/2] rcu-tasks: add RCU-tasks self tests Message-Id: <20210218140307.71f475248ebefa0ca613c09e@kernel.org> In-Reply-To: <20210217181738.GE2743@paulmck-ThinkPad-P72> References: <20210212192059.wytqwdf4qm4rnq3d@linutronix.de> <20210212211207.GA2046@pc638.lan> <20210212234851.GP2743@paulmck-ThinkPad-P72> <20210213003709.GA27846@paulmck-ThinkPad-P72> <20210213004328.GB27846@paulmck-ThinkPad-P72> <20210213113030.GA1878@pc638.lan> <20210213164554.GS2743@paulmck-ThinkPad-P72> <20210215112826.xc6b4se6ujwvrwco@linutronix.de> <20210216173003.GX2743@paulmck-ThinkPad-P72> <20210217234759.b82e39049a2e99cf6358e1c2@kernel.org> <20210217181738.GE2743@paulmck-ThinkPad-P72> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 17 Feb 2021 10:17:38 -0800 "Paul E. McKenney" wrote: > > > 1. Spawn ksoftirqd earlier. > > > > > > 2. Suppress attempts to awaken ksoftirqd before it exists, > > > forcing all ksoftirq execution on the back of interrupts. > > > > > > Uladzislau and I each produced patches for #1, and I produced a patch > > > for #2. > > > > > > The only other option I know of is to push the call to init_kprobes() > > > later in the boot sequence, perhaps to its original subsys_initcall(), > > > or maybe only as late as core_initcall(). I added Masami and Steve on > > > CC for their thoughts on this. > > > > > > Is there some other proper fix that I am missing? > > > > Oh, I missed that the synchronize_rcu_tasks() will be involved the kprobes > > in early stage. Does the problem only exist in the synchronize_rcu_tasks() > > instead of synchronize_rcu()? If so I can just stop optimizer in early stage > > because I just want to enable kprobes in early stage, but not optprobes. > > > > Does the following patch help? > > It does look to me like it would! I clearly should have asked you about > this a couple of months ago. ;-) > > The proof of the pudding would be whether the powerpc guys can apply > this to v5.10-rc7 and have their kernel come up without hanging at boot. Who could I ask for testing this patch, Uladzislau? I think the test machine which enough slow or the kernel has much initcall to run optimization thread while booting. In my environment, I could not reproduce that issue because the optimizer was sheduled after some tick passed. At that point, ksoftirqd has already been initialized. Thank you, -- Masami Hiramatsu