RE: [PATCH 0/8] git pull request for tip/tracing/core

From: Luck, Tony
Date: Wed Feb 11 2009 - 13:34:52 EST


> The bits in question is really the number of possible nested interrupts
> that can happen. We take the paranoid approach that we can have a max
> nesting of NR_IRQS. Perhaps this can be changed, and just do a max of
> 1<<10 nesting? And have a big warn on if it happens to be bigger, or fall
> to another counter if it is bigger.
>
> 1000 nested IRQs seems a bit extreme :-/

Ah, I see. Then the answer is very different. The number of nested
interrupts possible on a cpu is limited by the number of priority
classes for interrupts (See Table 5-8 on page 2:112 of the Itanium
software developers manual). Effectively the max nesting depth is
16.

1000 nested interrupts would be certain to run us out of stack.

-Tony
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