Re: linux interrupt handling problem

Linus Torvalds (torvalds@transmeta.com)
Tue, 9 Nov 1999 11:01:56 -0800 (PST)

On Tue, 9 Nov 1999, Roman Zippel wrote:
> On Tue, 9 Nov 1999, Linus Torvalds wrote:
>
> > That is in fact what Linux/SMP does in various situations: a "sti()" in an
> > interrupt handler on SMP/i386 will be just a "local" sti(), while ir in
> > normal situations will be a "global" sti().
>
> That's the software version of priorities, on m68k this can be realized in
> hardware with 7 levels,

No it isn't, and no it can't.

The local vs global is much more than interrupt levels, it's really about
conditional code where "sti()" behaves very fundamentally differently
inside an interrupt handler.

The m68k irq levels are just another interrupt controller. A very stupid
one, admittedly, but an interrupt controller none-the-less.

Linus

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