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 2A284CCA482 for ; Tue, 14 Jun 2022 16:42:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243579AbiFNQmf (ORCPT ); Tue, 14 Jun 2022 12:42:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343541AbiFNQm2 (ORCPT ); Tue, 14 Jun 2022 12:42:28 -0400 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 92490DED3; Tue, 14 Jun 2022 09:42:26 -0700 (PDT) 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=47+tWvYfTyzzIcAfKg2dikUAXvzTciJT7x9ArpBU0cQ=; b=WhjpnYz1DKB/ghxhQBYKZr1QWz 84Rt1GI0YXBpWpQ+Rpq7OdaNTLjSPvHCVKLFiVIOCLsRCFy4DqvtOiDgSLHRe8OVkGLFTex3SSmV8 GohZ4ojxrTeP3ET5b4IFii7FfH5UbRGPxexOa+//wX1ieayjZ2GRIBUTTRmWuqKFS+bMiVDFKRSHa IV/MEvx0ElZNGt7kUqMr8NdHhRUFOmSCcqPcU9jSeSr7SVt4T0z3jKsQ6pCYU45ZyxeCj6DorIHXj CZmBSb2KSbTYN4gQwzBcOOqwVgJL0yEm9Ud5o0YTPtfXZ0pRZucUs+sMUdTCsznw5yKZXiWmZw8aF sEV0aFJg==; Received: from dhcp-077-249-017-003.chello.nl ([77.249.17.3] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1o19cQ-007uQx-LB; Tue, 14 Jun 2022 16:42:19 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 224823000E3; Tue, 14 Jun 2022 18:42:15 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 123E028B3F62D; Tue, 14 Jun 2022 18:42:15 +0200 (CEST) Date: Tue, 14 Jun 2022 18:42:14 +0200 From: Peter Zijlstra To: Mark Rutland Cc: rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@hansenpartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, pmladek@suse.com, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 15/36] cpuidle,cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}() Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144516.871305980@infradead.org> 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-csky@vger.kernel.org On Tue, Jun 14, 2022 at 05:13:16PM +0100, Mark Rutland wrote: > On Wed, Jun 08, 2022 at 04:27:38PM +0200, Peter Zijlstra wrote: > > All callers should still have RCU enabled. > > IIUC with that true we should be able to drop the RCU_NONIDLE() from > drivers/perf/arm_pmu.c, as we only needed that for an invocation via a pm > notifier. > > I should be able to give that a spin on some hardware. > > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/cpu_pm.c | 9 --------- > > 1 file changed, 9 deletions(-) > > > > --- a/kernel/cpu_pm.c > > +++ b/kernel/cpu_pm.c > > @@ -30,16 +30,9 @@ static int cpu_pm_notify(enum cpu_pm_eve > > { > > int ret; > > > > - /* > > - * This introduces a RCU read critical section, which could be > > - * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know > > - * this. > > - */ > > - rcu_irq_enter_irqson(); > > rcu_read_lock(); > > ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL); > > rcu_read_unlock(); > > - rcu_irq_exit_irqson(); > > To make this easier to debug, is it worth adding an assertion that RCU is > watching here? e.g. > > RCU_LOCKDEP_WARN(!rcu_is_watching(), > "cpu_pm_notify() used illegally from EQS"); > My understanding is that rcu_read_lock() implies something along those lines when PROVE_RCU.