I've given this some more thought, and I'm coming to the conclusion that 
a pure array-based implementation for holding cached_info (getting rid 
of the lists) would work well for the vast majority of cases in which 
OProfile will be used.  Yes, it is true that the mapping of an SPU 
context to a phsyical spu-numbered array location cannot be guaranteed 
to stay valid, and that's why I discard the cached_info at that array 
location when the SPU task is switched out.  Yes, it would be terribly 
inefficient if the same SPU task gets switched back in later and we 
would have to recreate the cached_info.  However, I contend that 
OProfile users are interested in profiling one application at a time. 
They are not going to want to muddy the waters with multiple SPU apps 
running at the same time.  I can't think of any reason why someone would 
conscisouly choose to do that.

Any thoughts from the general community, especially OProfile users?

Well, it's my understanding that quite a few typical usage scenario
involve different tasks running on different SPUs passing each other
data around.

Ben.