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 69B97C433F5 for ; Tue, 8 Feb 2022 18:56:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385555AbiBHS41 (ORCPT ); Tue, 8 Feb 2022 13:56:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244274AbiBHS4Y (ORCPT ); Tue, 8 Feb 2022 13:56:24 -0500 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EDD3C0613CB; Tue, 8 Feb 2022 10:56:23 -0800 (PST) Received: by mail-pj1-x102f.google.com with SMTP id t14-20020a17090a3e4e00b001b8f6032d96so2625213pjm.2; Tue, 08 Feb 2022 10:56:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=yeJo/5hRrRCyM2Jlw/wQyb6VESGf89gzXf+99lk7a3A=; b=FgXOB2hB2inJYKtI8UTi1vhmT/jH47kpKuzq3ZMCZb5yW1Yur9p0av+LCMiF0KmOCm 8uj8z+CeQrwdAXzc99xk9QOR43b/6OV4H9IDViFxOF9JIpk67dSU3t+67ax9WJcZeIvb Cnu4pChuxVQ+IkuMOUdlP6g0nfsG/Y7CZbroTNarO5AZMV/pUkua1pULsJpmRjFJrzDb Jdy49h0K2QW5qQNM7joc55BAMkbWWIfdvZZftvLPG2Z1pNbl9qRXeR5W8hly0TZbZwlJ QwjqmeubH6D8bZkLrwXMf7t9ShWiajbusghkt0ayHmnDnnG/bNaspO0S4LAM2fqZZObb Toiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=yeJo/5hRrRCyM2Jlw/wQyb6VESGf89gzXf+99lk7a3A=; b=yf+RaRC0AHB+WsNI2IPajlXpbwOTAU6HDX8d0dUbCAshdwPtsiZGc4y0D+UQDPunGd F1X/TWABYf0j1fJno+uNkKm6nqxpAIYAZMNdu6yt37sCAWIeDpzNmu0vXTZTN663q70b S55mjfZ1G48pgDH2BbVMmMJlT6Q+C+5uI1gntm6pbvZup/bmbwQa4KrGZqCrGiVSGK5F FabLLmJmDj0J+QQ2haGA1QWwt41Afbml2wl5oxS+JoU/OK+Hf0ixx8NPwgwdxolMHRfm hB4fIugn1UuqipZvjW0MUDjD5W/wyROo1cL/IRHk7bZgCQLt7qJ8egB1WS9fTugeQEMv VszQ== X-Gm-Message-State: AOAM5327Hvbw0+Iama/2Vfdre4K65egLscVCI/C5K9ZsiEbucM6yqkbr MUv0xuAxnrqN6CmNptwAimOKJu4/NV8= X-Google-Smtp-Source: ABdhPJzNZbZrbclkhIGMjgr6jnTBCIGd7035cZq8xL4tSAq9c/zh578nWHZgv101gyl1ot5pbnemMg== X-Received: by 2002:a17:90a:8e84:: with SMTP id f4mr2828258pjo.215.1644346582712; Tue, 08 Feb 2022 10:56:22 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-e24f-43ff-fee6-449f.res6.spectrum.com. [2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id z13sm17177810pfj.23.2022.02.08.10.56.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Feb 2022 10:56:22 -0800 (PST) Sender: Tejun Heo Date: Tue, 8 Feb 2022 08:56:20 -1000 From: Tejun Heo To: "Paul E. McKenney" Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Mukesh Ojha Subject: Re: [PATCH rcu 3/3] rcu: Allow expedited RCU grace periods on incoming CPUs Message-ID: References: <20220204225409.GA4193020@paulmck-ThinkPad-P17-Gen-1> <20220204225507.4193113-3-paulmck@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220204225507.4193113-3-paulmck@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 04, 2022 at 02:55:07PM -0800, Paul E. McKenney wrote: > Although it is usually safe to invoke synchronize_rcu_expedited() from a > preemption-enabled CPU-hotplug notifier, if it is invoked from a notifier > between CPUHP_AP_RCUTREE_ONLINE and CPUHP_AP_ACTIVE, its attempts to > invoke a workqueue handler will hang due to RCU waiting on a CPU that > the scheduler is not paying attention to. This commit therefore expands > use of the existing workqueue-independent synchronize_rcu_expedited() > from early boot to also include CPUs that are being hotplugged. > > Link: https://lore.kernel.org/lkml/7359f994-8aaf-3cea-f5cf-c0d3929689d6@quicinc.com/ > Reported-by: Mukesh Ojha > Cc: Tejun Heo > Signed-off-by: Paul E. McKenney Acked-by: Tejun Heo Thanks. -- tejun