Re: [Valgrind-users] Assertion Failed

[Tom H. <th...@cy...>]

In message <200...@ac...>
          Julian Seward <js...@ac...> wrote:

> 
> > > valgrind: vg_ldt.c:167 (vgPlain_do_useseg): Assertion `(seg_selector &
> > > 7) == 7'
> 
> > The fact that this assertion is talking about segment selectors
> > suggests that thread local storage is involved, and hence this is
> > probably a threading related problem.
> 
> The lowest 3 bits of the segment selector is a tag which indicates some
> properties of the segment (iirc).  111b means a LDT selector, and that's
> what the above assertion tests.   I think you've probably hit a
> GDT selector (011b iirc).

I suspect the same - the NPTL documentation does mention that it
uses the GDT to handle thread local storage instead of the LDT that
is used by the old threading system.

There is also a new system call, tls, to manage the GDT so valgrind
is probably going to need to intercept that and emulate the GDT in a
similar way to that the LDT emulation is does at the moment.

Tom

-- 
Tom Hughes (th...@cy...)
Software Engineer, Cyberscience Corporation
http://www.cyberscience.com/