On Jul 24, 2008, at 9:37 AM, Jason Thorpe wrote:
quoted text
> The right model for that is to use a continuation.  Threads by their  
> nature have stacks and other resources that make them too  
> heavyweight to be appropriate for this type of processing.

No argument here.   However, in practice there's no decent scheme  
compiler to use for this, so people wind up doing it in C with threads  
or state threads.   In my experience, the cases where you need threads  
and not continuations are rare, and a lot of extra work is needed when  
doing threads that's completely unnecessary.   Nevertheless, people  
persist in programming in C because there are good compilers, and  
continuations are...   hard...  in C.

Anyway, the more I think about this the more it seems to me that the  
need being discussed is specialized, and therefore probably doesn't  
need to be addressed by the default libc.   It still seems like the  
work Bill is doing is worthwhile in this case, if a consequence of it  
is that someone who needs this functionality on their OLPC can choose  
the SCHEDULER_ACTIVATIONS option in the kernel and build a libc that  
will do what they want.