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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DC6DFC433FE for ; Wed, 11 May 2022 08:12:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=+KW58wMhJ0dO+p7GMi7pyYTVYGgmBID3joN1nvMWtfg=; b=fKZEDXEXGgRbBa HGCgzswnhpcVi90JGg5db3nyxuguz6k4HkCeII3VavUgGTHdo4KwUAdYJAMIrIRiKfBwge5NRFQcJ CWJHuwh5LzBLcoJ/o4v57peR1JJp6kP+tAHaa4tOadI4PVTd8X1W5RXxRt4V6b0K7w4YfSPF8mHxY GhquPsvc3d+pLeMHK3cjVggmXmh1VHuCTebznc9KsR+91DVJB43qVvRmY3q30MqBu4DQJ8CtjBy+F zTHlCIRmXfna3QCnyo0wufzqzmbb9N0hDlipdwdCH4iRFHTGhDjI3ml7xeCCZkmegpMvSg/9IInhF 5FCh2tCG9sF+OBvMQFkw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nohRC-005qig-SJ; Wed, 11 May 2022 08:11:15 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nohR9-005qgU-9Q for linux-arm-kernel@lists.infradead.org; Wed, 11 May 2022 08:11:12 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CB718106F; Wed, 11 May 2022 01:11:09 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.3.187]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1A9853F73D; Wed, 11 May 2022 01:11:05 -0700 (PDT) Date: Wed, 11 May 2022 09:11:02 +0100 From: Mark Rutland To: Thomas Gleixner Cc: Lukas Wunner , maz@kernel.org, Linus Walleij , Bartosz Golaszewski , linux-gpio@vger.kernel.org, Octavian Purdila , linux-kernel@vger.kernel.org, aou@eecs.berkeley.edu, catalin.marinas@arm.com, deanbo422@gmail.com, green.hu@gmail.com, guoren@kernel.org, jonas@southpole.se, kernelfans@gmail.com, linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk, palmer@dabbelt.com, paul.walmsley@sifive.com, shorne@gmail.com, stefan.kristiansson@saunalahti.fi, tsbogend@alpha.franken.de, vgupta@kernel.org, vladimir.murzin@arm.com, will@kernel.org Subject: Re: [PATCH v2 17/17] irq: remove handle_domain_{irq,nmi}() Message-ID: References: <20211026092504.27071-1-mark.rutland@arm.com> <20211026092504.27071-18-mark.rutland@arm.com> <20220506203242.GA1855@wunner.de> <20220510121320.GA3020@wunner.de> <874k1xorlj.ffs@tglx> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <874k1xorlj.ffs@tglx> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220511_011111_426806_53126629 X-CRM114-Status: GOOD ( 24.73 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 11, 2022 at 02:11:52AM +0200, Thomas Gleixner wrote: > On Tue, May 10 2022 at 15:15, Mark Rutland wrote: > > On Tue, May 10, 2022 at 02:13:20PM +0200, Lukas Wunner wrote: > >> Actually, since you're mentioning the in_nmi() check, I suspect > >> there's another problem here: > >> > >> generic_handle_domain_nmi() warns if !in_nmi(), then calls down > >> to handle_irq_desc() which warns if !in_hardirq(). Doesn't this > >> cause a false-positive !in_hardirq() warning for a NMI on GIC/GICv3? > > > > I agree that doesn't look right. > > > >> The only driver calling request_nmi() or request_percpu_nmi() is > >> drivers/perf/arm_pmu.c. So that's the only one affected. > >> You may want to test if that driver indeed exhibits such a > >> false-positive warning since c16816acd086. > > > > In testing with v5.18-rc5, I can't see that going wrong. > > > > I also hacked the following in: > > > > -------->8-------- > > diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c > > index 939d21cd55c38..3c85608a8779f 100644 > > --- a/kernel/irq/irqdesc.c > > +++ b/kernel/irq/irqdesc.c > > @@ -718,6 +718,7 @@ EXPORT_SYMBOL_GPL(generic_handle_domain_irq); > > int generic_handle_domain_nmi(struct irq_domain *domain, unsigned int hwirq) > > { > > WARN_ON_ONCE(!in_nmi()); > > + WARN_ON_ONCE(!in_hardirq()); > > return handle_irq_desc(irq_resolve_mapping(domain, hwirq)); > > which is pointless because NMI entry code has to invoke [__]nmi_enter() > before invoking this function. [__]nmi_enter() does: > > __preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); > > So it's more than bloody obvious why there is no warning triggered for a > regular hardware induced NMI invocation. Ugh, yes; clearly I need new eyes and/or more sleep. I entirely missed that we treat an NMI as *also* being a hardirq rather than something completely independent, and that means that this is *not* a problem for NMI. Thanks for pointing that out! > For a software invocation from the wrong context it does not matter how > many redundant WARN_ONs you add. The existing ones are covering it > nicely already. Yup; as above I was clearly not thinknig straight here. Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel