Re: RT and Cascade interrupts

From: john cooper
Date: Fri May 13 2005 - 08:14:59 EST

Ingo Molnar wrote:
* Daniel Walker <dwalker@xxxxxxxxxx> wrote:

It seems like the cascade interrupts could run in threads, but i386 doesn't, and I know ARM crashed with cascades in threads. You may have a bit of a slow down, but it seems possible. Does anyone have some reasoning for why we aren't running the cascades in threads?

are the x86 cascade interrupts real ones in fact? Normally they should never trigger directly. (except on ARM which has a completely different notion of cascade irq)

I just caught this thread in the corner of my eye.

I'm seeing the BUG assert in kernel/timers.c:cascade()
kick in (tmp->base is somehow 0) during a test which
creates a few tasks of priority higher than ksoftirqd.
This race doesn't happen if ksoftirqd's priority is
elevated (eg: chrt -f -p 75 2) so the -RT patch might
be opening up a window here.

I'm in the process of investigating this and see a few
potential suspects but was wondering if anyone else has
seen this behavior?


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