On Mon, 09 Aug 2004 17:08:57 -0400 Lee Revell <rlrevell@xxxxxxxxxxx> wrote: > I think Linux does not have ipls as such. When an interrupt handler > is running it blocks further interrupts from the same source, but > without the voluntary preempt patch, an interrupt from the disk will > interrupt the soundcard interrupt handler. If you were to extend this > scheme to support more than one priority (as opposed to 'this > interrupt source' vs'other interrupt source'), you would have IPLs. hi, i have to ask again, because there are still some unclarities for me: from links like this http://roht.informatik.uni-halle.de/~ladischc/linux_interrupt_priorities.html i get to the conclusion that there indeed was a hierarchy of IRQ's in the traditional IRQ handlers in linux. I think this priority is located in the PIC itself. I just don't know exactly how to understand the implications. Does this priority only apply to irqs which happen to happen on the exact same pci bus cycle? So, if soundcard and hd raise an interrupt at the same time, the one with the higher PIC priority gets precedence.. All this is still independent of the linux IRQ handlers. I assume these PIC priorities still are effective when using threaded IRQ handlers. Now the question is: what happens in linux' traditional IRQ handler? Does it honour PIC priorities? Let's assume an ide controller IRQ has occured. Linux will handle it by running this irq's handler. This irq handler disables further IRQ's from the same ide controller while it runs. And reenable them when it finishes. Now during the running of the irq handler a soundcard IRQ occurs. What happens? Does the PIC priority have any influence on if the the Soundcards irq handler preempts the ide-controller irq handler? Or does an irq from another source _always_ preempt irq handlers from other sources? In the case of threaded handlers this is pretty clear. Only higher priority [not PIC priority but task priority] irq handlers will preempt lower priority ones. But in the case of traditional handlers? Flo -- Palimm Palimm! http://affenbande.org/~tapas/
