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    SubjectRe: linux interrupt handling problem
    Hi,

    On Tue, 9 Nov 1999, Richard B. Johnson wrote:

    > It works fine without an interrupt controller. It works in the Power PC.
    > Please look at the dispatch handler in ../arch/ppc/kernel/irq.c.

    The ppc has a different interrupt architecture, it has only a single
    interrupt entry and a single interrupt priority (on/off). In that file
    there is also a mask_and_ack_irq(irq) _before_ that loop. The m68k cpu is
    completly different here, it has multiple entries and multiple priorities
    (0-7) and the acknowledgement needs sometimes also to be done within that
    loop by the driver, so it doesn't work anymore.
    The requirement for a sti() in interrupts makes it impossible to utilize
    these priorities to achieve better interrupt perfomance. What other people
    sometimes would like to have - the ability to preempt slow interrupts -
    get we for free implemented in hardware, but we can't use it because of
    the above requirement. :(

    bye, Roman



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