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SubjectRe: Strange interrupt behaviour
On Sun, Jul 12, 1998 at 04:18:28AM +0200, Richard B. Johnson wrote:
> On 11 Jul 1998, Andi Kleen wrote:
>
> > alan@lxorguk.ukuu.org.uk (Alan Cox) writes:
> >
> > > 3. Drivers that get repeated interrupts appear to re-enter the handler
> > > uncontrollably blow the stack and crash. I suspect nested interrupt
> > > handling problems may be half the 8K stack issue, and could be tons
> > > of our other remaining bugs.
> >
> > How about using a separate per-CPU 16K stack for interrupts, instead of
> > handling them on the per-process kernel stack? Then we could probably
> > switch back to 4K process kernel stacks too.
> >
>
> No. That just masks the problem. It is common for Linux interrupt handlers
> to enable interrupts. They must _not_ be reentered. The kernel IRQ code
> should:

It would be generally useful to handle nested interrupt of different
kinds (higher priority irq A interrupts irq B).

If it means that the per-process stacks can be shrinked to 4K again it
is definitely a win.

A separate interrupt stack has another big advantage: It is more cache
friendly. All interrupts will use the same piece of memory, not "cycle
around" the stacks of all active threads.

-Andi


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