1:N threading

[Peter Wemm]

Daniel Eischen wrote:
> On Thu, 3 Apr 2003, Peter Wemm wrote:
> 
> > 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 */
> 
> OK, but if NLDT is kernel private, how do can I know
> what LDTs I can use as local?

Whoops.  I misread NLDT as NGDT.

Gah.  We're doing some crufty stuff here.  For starters, we're running
userland on a LDT for %cs and %ds/es/ss/etc.  We really should be using a
GDT slot for those.  Most of the other stuff there is for the a.out
"lcall 7,0" instruction and for BSDI's version of the lcall stuff.

The i386_[gs]et_ldt() syscalls really should have a way of reporting what
is available for use.

Cheers,
-Peter
--
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5