Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764483AbZANQwm (ORCPT ); Wed, 14 Jan 2009 11:52:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763043AbZANQwc (ORCPT ); Wed, 14 Jan 2009 11:52:32 -0500 Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:26820 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762911AbZANQwb (ORCPT ); Wed, 14 Jan 2009 11:52:31 -0500 From: Bjorn Helgaas To: Olaf Dabrunz Subject: Re: PCI, ACPI, IRQ, IOAPIC: reroute PCI interrupt to legacy boot interrupt equivalent Date: Wed, 14 Jan 2009 09:52:24 -0700 User-Agent: KMail/1.9.10 Cc: Stefan Assmann , Shaohua Li , Len Brown , Ingo Molnar , Jesse Barnes , Thomas Gleixner , Steven Rostedt , Linux Kernel Mailing List , "linux-acpi@vger.kernel.org" , Sven Dietrich References: <200901140848.08531.bjorn.helgaas@hp.com> <20090114155529.GP25512@suse.de> In-Reply-To: <20090114155529.GP25512@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200901140952.24757.bjorn.helgaas@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1625 Lines: 34 On Wednesday 14 January 2009 08:55:29 am Olaf Dabrunz wrote: > On 14-Jan-09, Bjorn Helgaas wrote: > > On Wednesday 14 January 2009 02:57:22 am Stefan Assmann wrote: > > > Shaohua Li wrote: > > > > So a device can generate interrupt from two irqs. And we can get the irq > > > > number for the routing table. Can we extend the irq mechanism and > > > > automatically register the interrupt handler for the two irqs? > > > > > > This would not solve the problem of asserting 2 different interrupt > > > lines, in the masked interrupt handling case, for 1 interrupt request. > > > The result would be that the ISR is called twice and at the second call > > > you can't be sure that the device hasn't already been serviced. > > > > Calling the ISR twice isn't a problem, is it? We're talking about > > PCI interrupts, which are shareable, so ISRs have to handle being > > called extra times. > > > > There's still the problem that the core will disable an IRQ if we > > take it too many times without any ISR that cares about it. But that's > > a core issue, not an ISR issue. > > It is not solvable in the core. How do you find out that the "nobody > cared" spurious IRQ is benign? Sorry, I'm not suggesting that you can. I was just trying to clarify that the problem is not with calling an ISR twice, but I think I only managed to muddy the discussion to no benefit. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/