libkse and SMP (was Re: USB bulk read & pthreads)

[Terry Lambert]

Daniel Eischen wrote:
> On Fri, 23 May 2003, Terry Lambert wrote:
> > I'm rereading it, but I don't see that interpretation.
> >
> > I guess if both you and Julian both called me on it, I must
> > have misexpressed myself, but I currently don't understand
> > how.  8-|.
> 
> I think it was the part about "a single CPU system with
> PTHREAD_SCOPE_PROCESS (the default) can still get itself
> blocked in the kernel by a single blocking call" without
> mentioning that it won't block other scope process
> threads from being run.

OK... this I don't get.  If the scope is process, and you
are implementing M:N, and N == 1, my understanding of the
code is that it will block exactly the same as libc_r.  If
it won't (and I'm prepared to believe this), then I'd like
to know "why not?"; it should be that there is a single
scheduling object, no?

Reading the code, I don't get that there will be the ability
to do multiple returns.  Is it that a KSEG is intended to
represent a quantum?  If so, I've just had an epiphany as to
why you would want KSEG's at all in the first place (I've
never agreed with Julian on KSEG's, since the earliest days,
and I've only reluctantly accepted their necessity as an
artifact of scheduling priority differences for a strictest
compliance with POSIX mandated semantics -- hence my defense
of them to Jeff when he wanted to change the kernel code to
make them semi-impossible).

-- Terry