Messages in this thread | | | Date | Tue, 16 Oct 2007 15:44:55 -0400 | From | Jeff Garzik <> | Subject | Re: MSI interrupts and disable_irq |
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Yinghai Lu wrote: > On 10/16/07, Jeff Garzik <jgarzik@pobox.com> wrote: >> Yinghai Lu wrote: >>> On 10/15/07, Jeff Garzik <jgarzik@pobox.com> 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
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