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SubjectRe: linux interrupt handling problem
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> Alan> performance. On modern machines and things like the PC what you
> Alan> say is very true but not on old m68k boxen
>
> I still don't see your point, if all non critical interrupts are
> running with sti(), then your critical one (ie. serial in this case)
> can interrupt any time. The serial handler is implemented so it runs
> with all other interrupts disabled, ie. it never gets disturbed by
> anyone.
>
> Where's the problem?

Tons of kernel code does

spin_lock_irqsave(...)
Sit around
spin_unlock_irqrestore(...)

On the 68K you really do want that to be spin_lock_irqsave_except_rtbits()

and you really do need that. It isnt even down to poor driver writing, the
timing constraints on an 8530 on an old 68K box are horrible.

Right now a mac68k is pushing it to do 19200 baud in Linux but with rt hacks
will do 115,200 and with irq path tidying should do 230,400


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