[PATCH] [POWERPC] Rework EXC_LEVEL_EXCEPTION_PROLOG code

[Gabriel Paubert]

On Thu, May 01, 2008 at 08:22:08AM -0500, Kumar Gala wrote:
> >>So we have 4 actual exceptions:
> >>* CriticalInput (some external device signaled this.  There are two
> >>concepts of critical.  One is error the other is high priority)
> >>However this would have the same caveats as any ExternalInput  
> >>handler.
> >
> >No, it's worse. It can interrupt code that normally has
> >local_irq_disabled() and thus doesn't expect to be interrupted. That
> >means that everything becomes unsafe including locks etc....
> 
> Fair.  Should local_irq_disable() clear MSR_SE & MSR_BE on classic  
> parts?
> 
> >Note that driver that want to make active use of that probably want  
> >some
> >explicit local_crit_irq_disable/enable functions to be able to  
> >implement
> >some sort of synchronization.
> 
> Or we could just have local_irq_disable -- clear MSR_EE and MSR_CE
> 
> >>* Watchdog - pretty severe if this fires.
> >>
> >>* Debug - user space debug is pretty straight forward.  However we
> >>have features like kprobes that require kernel level support.
> >
> >Which means we have to be extra careful, in fact, I consider it a  
> >design
> >bug of BookE to have made debug be a critical interrupt...
> 
> I consider the whole BookE debug arch a design bug :)

Why only the debug part? :-)

	Gabriel