Re: RT and Cascade interrupts

[john cooper]

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?

-john

--
john.cooper@xxxxxxxxxxx
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