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spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=NoO9Uhl1DcWatw9NxwlOMmfFwLVG86wAMooJZNtd6p4=; b=xpNHM8P6MLEvZ7kFr2jSjVMKL xBj0hHzRLiz2h/x6Pgvzs2unm20l3TBI8y8yDiq4bRNfBy/lZprxCY2UKmCVFwEn5dSsHREjrh3Kg 1i2xNWRn97c/zr2FlF8PsiAqPFyFeznFurczHQy0UGmzRpPhS2y5l8hpfQDKiuaocfLiB64sbKKXv bZJNPKqKxlr7fXUo4dPKilq0QNBpJKDPCx/xC59EapFUaBrG6S4hCEG5zJvak9sGjfTMyXEl/WlHH gfxXollybIwfiZAiOhT2/wiJT+qVC+F3eDN9LoURra40k5LeyFWbtD4vudR+1zGTOGsKABrRMZsJx Xi3tw7P1w==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lE9yp-0001Ll-75; Mon, 22 Feb 2021 12:06:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lE9ym-0001Kp-Hx for linux-arm-kernel@lists.infradead.org; Mon, 22 Feb 2021 12:06:21 +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 B89751FB; Mon, 22 Feb 2021 04:06:18 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.51.127]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DBB993F70D; Mon, 22 Feb 2021 04:06:16 -0800 (PST) Date: Mon, 22 Feb 2021 12:06:14 +0000 From: Mark Rutland To: Marc Zyngier Subject: Re: [PATCH 5/8] arm64: irq: add a default handle_irq panic function Message-ID: <20210222120614.GC70951@C02TD0UTHF1T.local> References: <20210219113904.41736-1-mark.rutland@arm.com> <20210219113904.41736-6-mark.rutland@arm.com> <20210222095913.GA70951@C02TD0UTHF1T.local> <1d2c27d72b9b2cbdb83d25165a20559a@kernel.org> <20210222112544.GB70951@C02TD0UTHF1T.local> <2e6a9659eabcccb355318ff7214c8d1f@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2e6a9659eabcccb355318ff7214c8d1f@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210222_070620_668049_7A398403 X-CRM114-Status: GOOD ( 27.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: catalin.marinas@arm.com, marcan@marcan.st, linux-kernel@vger.kernel.org, james.morse@arm.com, tglx@linutronix.de, will@kernel.org, linux-arm-kernel@lists.infradead.org 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 Mon, Feb 22, 2021 at 11:43:13AM +0000, Marc Zyngier wrote: > On 2021-02-22 11:25, Mark Rutland wrote: > > On Mon, Feb 22, 2021 at 10:48:11AM +0000, Marc Zyngier wrote: > > > On 2021-02-22 09:59, Mark Rutland wrote: > > > > On Fri, Feb 19, 2021 at 11:39:01AM +0000, Mark Rutland wrote: > > > > > +void (*handle_arch_irq)(struct pt_regs *) __ro_after_init = > > > > > default_handle_irq; > > > > > > > > > > int __init set_handle_irq(void (*handle_irq)(struct pt_regs *)) > > > > > { > > > > > - if (handle_arch_irq) > > > > > + if (handle_arch_irq != default_handle_irq) > > > > > return -EBUSY; > > > > > > > > > > handle_arch_irq = handle_irq; > > > > > @@ -87,7 +92,7 @@ void __init init_IRQ(void) > > > > > init_irq_stacks(); > > > > > init_irq_scs(); > > > > > irqchip_init(); > > > > > - if (!handle_arch_irq) > > > > > + if (handle_arch_irq == default_handle_irq) > > > > > panic("No interrupt controller found."); > > > > > > It also seems odd to have both default_handle_irq() that panics, > > > and init_IRQ that panics as well. Not a big deal, but maybe > > > we should just drop this altogether and get the firework on the > > > first interrupt. > > > > My gut feeling was that both were useful, and served slightly different > > cases: > > > > * The panic in default_handle_irq() helps if we unexpectedly unmask IRQ > > too early. This is mostly a nicety over the current behaviour of > > branching to NULL in this case. > > > > * The panic in init_IRQ() gives us a consistent point at which we can > > note the absence of a root IRQ controller even if all IRQs are > > quiescent. This is a bit nicer to debug than seeing a load of driver > > probes fail their request_irq() or whatever. > > > > ... so I'd err on the side of keeping both, but if you think otherwise > > I'm happy to change this. > > As I said, it's not a big deal. I doubt that we'll see default_handle_irq() > exploding in practice. But the real nit here is the difference of treatment > between IRQ and FIQ. *IF* we ever get a system that only signals its > interrupt as FIQ (and I don't see why we'd forbid that), then we would That's a fair point. For consistency, we could remove the init_IRQ() panic() and instead log the registered handlers, e.g. | pr_info("Root IRQ handler is %ps\n", handle_arch_irq); | pr_info("Root FIQ handler is %ps\n", handle_arch_fiq); ... or do that inside the set_handle_{irq,fiq}() functions. That way the messages (or absence thereof) would be sufficient to diagnose the lack of a root IRQ/FIQ handler when IRQ/FIQ happens to be quiescent. Does that sound any better? > To be clear, I don't think we should care too much either way, and I'm > fine with the code as is. Sure, and FWIW I agree with the nit! Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel