Subject: Re: [PATCH HACK] powerpc: quick hack to get a functional eHEA with hardirq preemption

From: Anton Vorontsov <[email-masked]>
Date: Tue, 16 Sep 2008 15:59:47 +0400

On Mon, Sep 15, 2008 at 03:13:32PM +0200, Sebastien Dugue wrote:
[...]
> > we are a bit worried about putting this into the mainstream part of non real
> > time linux.
> 
>   Heck, I sure do not want this to be applied mainstream nor into any tree.
> The sole purpose of this patch was to trigger some reaction from the people who
> know the hardware and try to understand where the problem lies.
> 
> > There interrupts work perfectly fine, and it was a bit of a
> > challenge to get there for all cases / configurations / machines.
> 
>   Agreed, but the fact that it fails with hardirq preemption leads me to
> believe (without any more knowledge about the harware) that there might be
> something amiss with this driver (or the code concerning the XICS)
> nevertheless.
> 
> > 
> > Could you try to enable these changes only for RT-Linux via a real-time
> > kconfig switch?
> 
>   Nope, this is just a quick hack that allows me to have a functional eHEA under
> the rt kernel. I want to understand what the problem is:
> 
>   - Is the eHEA really delivering level interrupts to the XICS?
> 
>   - Is the XICS loosing interrupts when they are masked?

There is a known bug in the -rt kernels, the bug causes handlers
to lose edge interrupts.

See this patch:

http://lkml.org/lkml/2008/6/30/372

>   - ...?

-- 
Anton Vorontsov
email: [email-masked]
irc://irc.freenode.net/bd2