Messages in this thread | | | Date | Tue, 16 Oct 2007 13:39:02 -0400 | From | Jeff Garzik <> | Subject | Re: MSI interrupts and disable_irq |
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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.
Jeff
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