Re: [PATCH] x86 Topology cpu_to_node parameter check

[Steven Rostedt]

On Fri, 3 Oct 2008, Mathieu Desnoyers wrote:

> * Steven Rostedt (rostedt@xxxxxxxxxxx) wrote:
> > 
> > On Fri, 3 Oct 2008, Mathieu Desnoyers wrote:
> > > 
> > > That's how I did it first, but then I looked at asm-generic/topology.h
> > > and have seen it uses #defines. Should we change them too ?
> > > 
> > 
> > The old way of doing this is with defines. But all new code should be 
> > static inline functions when feasible. This way we can get typechecking 
> > on the parameters even when the configuration is disabled.
> > 
> > Even if the rest of the file uses defines, the new code should be
> > static inlines. Eventually, even the old defines will be converted.
> > 
> > -- Steve
> > 
> 
> Argh, I think topology.h is utterly broken :-(
> 
> Have you noticed the subtile interaction between the
> 
> include/asm-x86/topology.h :
> 
> #define numa_node_id()          0
> #define cpu_to_node(cpu)        0
> #define early_cpu_to_node(cpu)  0
> ...
> #include <asm-generic/topology.h>
> 
> 
> and
> include/asm-generic/topology.h :
> #ifndef cpu_to_node
> #define cpu_to_node(cpu)        ((void)(cpu),0)
> #endif
> 
> If any architecture decide for some reason to use a static inline rather
> than a define, as currently done with node_to_first_cpu :
> 
> include/asm-x86/topology.h :
> static inline int node_to_first_cpu(int node)
> {
>         return first_cpu(cpu_online_map);
> }
> ...
> #include <asm-generic/topology.h>
> 
> include/asm-generic/topology.h :
> #ifndef node_to_first_cpu
> #define node_to_first_cpu(node) ((void)(node),0)
> #endif
> 
> (which will override the static inline !)
> 
> It results in an override of the arch-specific version. Nice eh ?

Seems that they expect cpu_to_node to be a macro if NUMA is not 
configured.

Actually, since the asm-generic/topology.h does have the cpu shown 
(although not in inline format), the solution here is to simply remove
the

#define cpu_to_node() 0

And we can still make the early_cpu_to_node a static inline since it is 
not referenced in the generic code.

-- Steve

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