1:N threading

[Jake Burkholder]

Apparently, On Thu, Apr 03, 2003 at 03:35:41PM -0800,
	Peter Wemm said words to the effect of;

> Daniel Eischen wrote:
> 
> > The patches are available:
> > 
> >   http://people.freebsd.org/~deischen/libpthread.diffs
> > 
> > FYI, since this is a new mailing list, the above changes
> > are meant to give libpthread M:N capability.
> > 
> > I don't need testers; I have enough bugs that I know about
> > to fix.
> 
> +	__asm__("movl %%gs, %0" : "=r" (id));
> +	id >>= 3;
> +	if (id - NLDT < 0)
> 
> There is a problem here, NLDT is kernel private and changes depending on
> things like whether SMP is enabled or what the maximum number of cpus
> is.
> 
> You're trying to find if its a local or global selector, right?
> What you really want is bit 2 which tells you which it is.
> 
> #define ISLDT(s)        ((s)&SEL_LDT)   /* is it local or global */
> #define SEL_LDT 4               /* local descriptor table */

NLDT seems to be invariant, but we should have a sysctl or something to
get the first LDT entry that is unused by the kernel.  Libthr uses it
in order to know which entry to start at.

Jake