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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74703C433FE for ; Fri, 1 Oct 2021 09:15:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 589A461A88 for ; Fri, 1 Oct 2021 09:15:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352876AbhJAJRG (ORCPT ); Fri, 1 Oct 2021 05:17:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:53902 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229792AbhJAJRD (ORCPT ); Fri, 1 Oct 2021 05:17:03 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 78BFF61A88; Fri, 1 Oct 2021 09:15:19 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mWEdR-00E9sE-I7; Fri, 01 Oct 2021 10:15:17 +0100 Date: Fri, 01 Oct 2021 10:15:16 +0100 Message-ID: <87sfxlrtqz.wl-maz@kernel.org> From: Marc Zyngier To: Pingfan Liu Cc: linux-arm-kernel@lists.infradead.org, Mark Rutland , "Paul E. McKenney" , Catalin Marinas , Will Deacon , Joey Gouly , Sami Tolvanen , Julien Thierry , Thomas Gleixner , Yuichi Ito , linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 1/3] kernel/irq: make irq_{enter,exit}() in handle_domain_irq() arch optional In-Reply-To: <20210930131708.35328-2-kernelfans@gmail.com> References: <20210930131708.35328-1-kernelfans@gmail.com> <20210930131708.35328-2-kernelfans@gmail.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: kernelfans@gmail.com, linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, paulmck@kernel.org, catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, samitolvanen@google.com, julien.thierry@arm.com, tglx@linutronix.de, ito-yuichi@fujitsu.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 30 Sep 2021 14:17:06 +0100, Pingfan Liu wrote: > > When an IRQ is taken, some accounting needs to be performed to enter and > exit IRQ context around the IRQ handler. Historically arch code would > leave this to the irqchip or core IRQ code, but these days we want this > to happen in exception entry code, and architectures such as arm64 do > this. > > Currently handle_domain_irq() performs this entry/exit accounting, and > if used on an architecture where the entry code also does this, the > entry/exit accounting will be performed twice per IRQ. This is > problematic as core RCU code such as rcu_is_cpu_rrupt_from_idle() > depends on this happening once per IRQ, and will not detect quescent > periods correctly, leading to stall warnings. > > As irqchip drivers which use handle_domain_irq() need to work on > architectures with or without their own entry/exit accounting, this > patch makes handle_domain_irq() conditionally perform the entry > accounting depending on a new HAVE_ARCH_IRQENTRY Kconfig symbol that > architectures can select if they perform this entry accounting > themselves. > > For architectures which do not select the symbol. there should be no > functional change as a result of this patch. > > Signed-off-by: Pingfan Liu > Reviewed-by: Mark Rutland > Cc: "Paul E. McKenney" > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Marc Zyngier > Cc: Joey Gouly > Cc: Sami Tolvanen > Cc: Julien Thierry > Cc: Thomas Gleixner > Cc: Yuichi Ito > Cc: linux-kernel@vger.kernel.org > To: linux-arm-kernel@lists.infradead.org > --- > kernel/irq/Kconfig | 3 +++ > kernel/irq/irqdesc.c | 4 ++++ > 2 files changed, 7 insertions(+) > > diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig > index fbc54c2a7f23..defa1db2d664 100644 > --- a/kernel/irq/Kconfig > +++ b/kernel/irq/Kconfig > @@ -100,6 +100,9 @@ config IRQ_MSI_IOMMU > config HANDLE_DOMAIN_IRQ > bool > > +config HAVE_ARCH_IRQENTRY > + bool > + > config IRQ_TIMINGS > bool > > diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c > index 4e3c29bb603c..fd5dd9d278b5 100644 > --- a/kernel/irq/irqdesc.c > +++ b/kernel/irq/irqdesc.c > @@ -693,7 +693,9 @@ int handle_domain_irq(struct irq_domain *domain, > struct irq_desc *desc; > int ret = 0; > > +#ifndef CONFIG_HAVE_ARCH_IRQENTRY > irq_enter(); > +#endif nit: I tend to prefer the 'if (!IS_ENABLED(CONFIG_*))' approach. > > /* The irqdomain code provides boundary checks */ > desc = irq_resolve_mapping(domain, hwirq); > @@ -702,7 +704,9 @@ int handle_domain_irq(struct irq_domain *domain, > else > ret = -EINVAL; > > +#ifndef CONFIG_HAVE_ARCH_IRQENTRY > irq_exit(); > +#endif > set_irq_regs(old_regs); > return ret; > } Apart from that: Reviewed-by: Marc Zyngier Thanks, M. -- Without deviation from the norm, progress is not possible.