From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935000AbXJPTp2 (ORCPT ); Tue, 16 Oct 2007 15:45:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760949AbXJPTpJ (ORCPT ); Tue, 16 Oct 2007 15:45:09 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:36776 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760659AbXJPTpH (ORCPT ); Tue, 16 Oct 2007 15:45:07 -0400 Message-ID: <471514B7.9080002@pobox.com> Date: Tue, 16 Oct 2007 15:44:55 -0400 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.5 (X11/20070727) MIME-Version: 1.0 To: Yinghai Lu CC: Manfred Spraul , Ayaz Abdulla , nedev , Linux Kernel Mailing List , David Miller , Andrew Morton Subject: Re: MSI interrupts and disable_irq References: <46FC15A9.1070803@nvidia.com> <46FDBCB4.9090802@pobox.com> <4710901F.8010206@colorfullife.com> <4713E713.9060702@pobox.com> <86802c440710161023p3fbd6832gdb6d10a1b5e9d932@mail.gmail.com> <4714F736.5000302@pobox.com> <86802c440710161059x17fdb4f2sb1b9582d64a883f9@mail.gmail.com> In-Reply-To: <86802c440710161059x17fdb4f2sb1b9582d64a883f9@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.1.9 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Yinghai Lu wrote: > On 10/16/07, Jeff Garzik wrote: >> Yinghai Lu wrote: >>> On 10/15/07, Jeff Garzik wrote: >>>> Manfred Spraul wrote: >>>>> Jeff Garzik wrote: >>>>>> I think the scenario you outline is an illustration of the approach's >>>>>> fragility: disable_irq() is a heavy hammer that originated with INTx, >>>>>> and it relies on a chip-specific disable method (kernel/irq/manage.c) >>>>>> that practically guarantees behavior will vary across MSI/INTx/etc. >>>>>> >>>>> I checked the code: IRQ_DISABLE is implemented in software, i.e. >>>>> handle_level_irq() only calls handle_IRQ_event() [and then the nic irq >>>>> handler] if IRQ_DISABLE is not set. >>>>> OTHO: The last trace looks as if nv_do_nic_poll() is interrupted by an irq. >>>>> >>>>> Perhaps something corrupts dev->irq? The irq is requested with >>>>> request_irq(np->pci_dev->irq, handler, IRQF_SHARED, dev->name, dev) >>>>> and disabled with >>>>> disable_irq_lockdep(dev->irq); >>>>> >>>>> Someone around with a MSI capable board? The forcedeth driver does >>>>> dev->irq = pci_dev->irq >>>>> in nv_probe(), especially before pci_enable_msi(). >>>>> Does pci_enable_msi() change pci_dev->irq? Then we would disable the >>>>> wrong interrupt.... >>>> Remember, fundamentally MSI-X is a one-to-many relationship, when you >>>> consider a single PCI device might have multiple vectors. >>> msi-x is using other entry >>> >>> if (np->msi_flags & NV_MSI_X_ENABLED) >>> >>> enable_irq_lockdep(np->msi_x_entry[NV_MSI_X_VECTOR_ALL].vector); >> Correct, but the overall point was that MSI-X conceptually conflicts >> with the existing "lockless" disable_irq() schedule, which was written >> when there was a one-one relationship between irq, PCI device, and work >> to be done. > > Can I use your new driver with RHEL 5 or RHEL 5.1? Not without modification, since it depends on the napi_struct work currently in torvalds/linux-2.6.git. But I am currently rewriting the fe-lock yet again, and most of those changes can be applied to pre-napi_struct forcedeth. Jeff