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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5715C61D90 for ; Tue, 21 Nov 2023 21:38:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5FB946B0291; Tue, 21 Nov 2023 16:38:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 584136B0294; Tue, 21 Nov 2023 16:38:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3D7C76B0292; Tue, 21 Nov 2023 16:38:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 299DB6B028C for ; Tue, 21 Nov 2023 16:38:32 -0500 (EST) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id F36C040B1E for ; Tue, 21 Nov 2023 21:38:31 +0000 (UTC) X-FDA: 81483275622.13.4D3131B Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf16.hostedemail.com (Postfix) with ESMTP id E2C0518001C for ; Tue, 21 Nov 2023 21:38:29 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of "SRS0=YbhT=HC=goodmis.org=rostedt@kernel.org" designates 145.40.73.55 as permitted sender) smtp.mailfrom="SRS0=YbhT=HC=goodmis.org=rostedt@kernel.org"; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1700602710; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xyAeqVR2RuIYHTfxbeZmtaNA/0a2zT1AiZRVxSa+K3k=; b=KyMPES43x5L0NjlHWalVC5XCyQGpIh75GIC/VjR/yWXhB+xEaHixi+SY4WEyEfodU4UxYa sehCJ34C7vsYcuDiwgG+TzLaU/kebXmqqOy2lxaRCDO+w0qv8okEw6cGy6m5EpGJSaO6v6 Kz9FKwBlJOu1EpnJtmFs7pNP51z6hOk= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1700602710; a=rsa-sha256; cv=none; b=oLnmfQBB1j0XYRqZlzg47356ynkoMIq95QZ+AAlHgURY03tsUAuwf2dv9vYV/YAkTshsAO 1z7KeypY5xz6n4drqsyoKMyykMufND2d95ONtBFv0YXgxmF1T/tJT3G4OqJ9zvJnhGf8Jh i1SYiZbRyzYmoJ6IKaUu2tNXu02e+kw= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of "SRS0=YbhT=HC=goodmis.org=rostedt@kernel.org" designates 145.40.73.55 as permitted sender) smtp.mailfrom="SRS0=YbhT=HC=goodmis.org=rostedt@kernel.org"; dmarc=none Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id C6797CE1DF5; Tue, 21 Nov 2023 21:38:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31E17C433C7; Tue, 21 Nov 2023 21:38:21 +0000 (UTC) Date: Tue, 21 Nov 2023 16:38:34 -0500 From: Steven Rostedt To: "Paul E. McKenney" Cc: Peter Zijlstra , 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, 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: <20231121163834.571abb52@gandalf.local.home> In-Reply-To: <1cdbb0f6-9078-4023-bf37-8d826ca0c711@paulmck-laptop> 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> <20231121203049.GN8262@noisy.programming.kicks-ass.net> <1cdbb0f6-9078-4023-bf37-8d826ca0c711@paulmck-laptop> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E2C0518001C X-Rspam-User: X-Stat-Signature: jbsmientdkurf87brfjmp9atu9h7a6jx X-Rspamd-Server: rspam03 X-HE-Tag: 1700602709-307521 X-HE-Meta: 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 VQ47lu9p xi64tu9p/D+kBwRaxSTeLO6zm0TIurqxRpEcQgl/IJdy4OvzNYeXXFv3NrRUqS9GWnXYMgMB1djVycP1GBBjS2ZjCM5x9dGN1XOl+XEC1qyNpHenqfqxfsQWSaKZEUVUeWCvLr4RGcS+XZRRhXcWv+vOKvS4du1XtsovA3vMtEUqoaqvKcG9C528ySqFrbuK8H1Xadx9eERUHOB3JL5qdDrYjf+AEY3TYT0X6DQ+YkHMtnUT1ql20WWLZspwmIN8L9yrDI4M9HdE7PwPEFY7o1AkkHyjxQSfCmTDY8tyhZeoetwRiEMjWVgKjsc5uc0hUQh1m3rLPtFnITJaEriA9P78tZR9jdW6kmY2e X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 21 Nov 2023 13:14:16 -0800 "Paul E. McKenney" wrote: > On Tue, Nov 21, 2023 at 09:30:49PM +0100, Peter Zijlstra wrote: > > 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()) \ Could we make the above an else case of the below if ? > > > 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. Note, the above is only true with "CONFIG_PREEMPT_RCU is not set", which keeps the preempt_count() for preemptable kernels with PREEMPT_RCU still minimal. -- Steve