KSE/ia64: NULL thread pointer in _thr_sig_add()

[Daniel Eischen]

On Sun, 17 Aug 2003, Marcel Moolenaar wrote:

> On Sun, Aug 17, 2003 at 08:54:56AM -0400, Daniel Eischen wrote:
> > > > 
> > > > One question.  When you call (the syscall) setcontext() from
> > > > _ia64_break_setcontext(), do you ignore the signal mask (uc.uc_sigmask)?
> > > 
> > > Good point. I don't think so.
> > 
> > OK, this will cause signal handling problems.  You can
> > use another flag, but that would dirty up MI setcontext().
> > Perhaps a separate ia64-specific system call?
> 
> I actually have been thinking about using a flag. One that simply
> indicates that the sigmask field is valid or not. The advantage
> of such flag is that it makes the general interaction with user
> land versions of getcontext() much more predictable and increases
> the overall applicability of the *context syscalls.
> 
> For example: libthr uses getcontext(2) but is not interested in
> the sigmask. It simply uses the syscall as an initialization for
> new threads. The context is passed to thr_create where we only
> use the mcontext part to setup the registers. libkse tries to
> avoid the syscalls. The userland versions don't save or restore
> signal masks. There too we use contexts without actually being
> interested in sigmasks. Also in libkse we see that the contexts
> created in the kernel and given to userland are not contexts that
> contains sigmasks. We simply copyout the mcontext part of the
> ucontext. So, it appears that most of our uses of contexts are
> such that we don't need to save and/or restore sigmasks.
> 
> I think an UCF_SIGMASK flag to indicate that the context has a
> valid sigmask is a logical or natural way to have setcontext(2)
> operate well with getcontext(2), which always defines contexts
> with sigmasks and userland versions of getcontext() or other
> more specific uses of contexts that may or may not have a need
> to save the sigmask.
> 
> Reasoning differently: if we were to introduce a new syscall,
> then the syscall would in effect be a clone of setcontext(2)
> with the difference that we don't restore a part of the context.
> This is duplication to avoid variation. Also, with a new syscall
> we introduce the notion of having 2 seperate contexts. This not
> only begs for a getcontext() clone that does not save the sigmask,
> but also begs for a flag to differentiate between those 2 contexts.

OK.  I mostly wanted to avoid #if defined(ia64) in kern_context.c
thinking the flag would have been in mc_flags.

Please get rid of UCF_SWAPPED while you're at it; it's no longer
used.

-- 
Dan Eischen