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 E6A0CC61D90 for ; Tue, 21 Nov 2023 20:32:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234346AbjKUUcS (ORCPT ); Tue, 21 Nov 2023 15:32:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40154 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234384AbjKUUcO (ORCPT ); Tue, 21 Nov 2023 15:32:14 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 406C51AA for ; Tue, 21 Nov 2023 12:32:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=mPcvVUr8HyRnp1aSDsAdvlimBvK+3BhX+aM2Alx5mqo=; b=mIrgR5qRdk0w3cvo6OGhGx+ybS ryPeZ+PXcYXTJUMdDd/bThNofQWboBYTG35XeXgxcoX08VW9Y9LgXs63MCtsCGudARZThuf+Hj1u5 ppZwOEc1du3571f7wiXafXNASbPLpf2QbZujF7DZ/3QjXwTcbBawhMW3DYDjkeJhxBkhaJ3CeNpKx tgDBWcScPDaxolJgzIpoeMZS6rJos5gjndFbrMrMsnFQ2tnR5/cXrJMl3g1fRSI2WNBtr4yRBCQmQ jHYZKGwZitUA6jlmR89mKmUfU4DJ4hLPRn8dqQnX3OyTSAv9G63vxXH1XVcf4s7BbGTpH9Mf5Si/2 LN2ub+Bg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1r5XOV-00BYNi-0M; Tue, 21 Nov 2023 20:30:52 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id D95D0300338; Tue, 21 Nov 2023 21:30:49 +0100 (CET) Date: Tue, 21 Nov 2023 21:30:49 +0100 From: Peter Zijlstra To: "Paul E. McKenney" Cc: Ankur Arora , linux-kernel@vger.kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, jgross@suse.com, andrew.cooper3@citrix.com, mingo@kernel.org, bristot@kernel.org, mathieu.desnoyers@efficios.com, geert@linux-m68k.org, glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com, mattst88@gmail.com, krypton@ulrich-teichert.org, rostedt@goodmis.org, David.Laight@aculab.com, richard@nod.at, mjguzik@gmail.com Subject: Re: [RFC PATCH 48/86] rcu: handle quiescent states for PREEMPT_RCU=n Message-ID: <20231121203049.GN8262@noisy.programming.kicks-ass.net> References: <20231107215742.363031-1-ankur.a.arora@oracle.com> <20231107215742.363031-49-ankur.a.arora@oracle.com> <2027da00-273d-41cf-b9e7-460776181083@paulmck-laptop> <87lear4wj6.fsf@oracle.com> <46a4c47a-ba1c-4776-a6f8-6c2146cbdd0d@paulmck-laptop> <31d50051-e42c-4ef2-a1ac-e45370c3752e@paulmck-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 21, 2023 at 11:25:18AM -0800, Paul E. McKenney wrote: > #define preempt_enable() \ > do { \ > barrier(); \ > if (!IS_ENABLED(CONFIG_PREEMPT_RCU) && raw_cpu_read(rcu_data.rcu_urgent_qs) && \ > (preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK | HARDIRQ_MASK | NMI_MASK) == PREEMPT_OFFSET) && > !irqs_disabled()) \ > rcu_all_qs(); \ > if (unlikely(preempt_count_dec_and_test())) { \ > __preempt_schedule(); \ > } \ > } while (0) Aaaaahhh, please no. We spend so much time reducing preempt_enable() to the minimal thing it is today, this will make it blow up into something giant again.