help on lost interrupt

help on lost interrupt

[Rajendra Prasad]

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Hi,

I was looking the source code of linux for ppc. In the interrupt
handling
there is a concept of lost_interrupt and do_lost_interrupt. I could not
understand why this is required and how it is managed on linux.

Is it something like interrupt is recognized by isr but not serviced by
the 
drivers and interrupt is left as disabled?

regards
Rajendra Prasad

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Re: help on lost interrupt

[Paul Mackerras]

Rajendra Prasad <prasadr@duettech.com> wrote:

> I was looking the source code of linux for ppc. In the interrupt
> handling
> there is a concept of lost_interrupt and do_lost_interrupt. I could not
> understand why this is required and how it is managed on linux.

With the interrupt controller on powermacs, if you disable an
interrupt in the interrupt controller, then the device requests an
interrupt, then you enable that interrupt in the interrupt controller,
the interrupt controller doesn't then request an interrupt from the
CPU.  So in that situation we set the corresponding bit in
lost_interrupts, and when interrupts get reenabled, we check if there
are any such interrupts that need to be serviced.

Paul.

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