From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Yinghai Lu" Subject: Re: MSI interrupts and disable_irq Date: Tue, 16 Oct 2007 10:59:41 -0700 Message-ID: <86802c440710161059x17fdb4f2sb1b9582d64a883f9@mail.gmail.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Manfred Spraul" , "Ayaz Abdulla" , nedev , "Linux Kernel Mailing List" , "David Miller" , "Andrew Morton" To: "Jeff Garzik" Return-path: Received: from wa-out-1112.google.com ([209.85.146.178]:56794 "EHLO wa-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762013AbXJPR7n (ORCPT ); Tue, 16 Oct 2007 13:59:43 -0400 Received: by wa-out-1112.google.com with SMTP id v27so2469648wah for ; Tue, 16 Oct 2007 10:59:41 -0700 (PDT) In-Reply-To: <4714F736.5000302@pobox.com> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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? YH