Re: kernel thread support - LWP's

Tim Hockin (thockin@isunix.it.ilstu.edu)
Sat, 17 Jul 1999 17:37:43 -0500 (CDT)

> >I remember someone (David Wragg <dpw@doc.ic.ac.uk>) once mentioned another
> >new flag idea: a CLONE_SIBLING flag, which will mean that if the new
> >thread does a clone() the new thread will get the same ppid of the parent.
> >This (together with the redefinition of the manager thread, above) will
> >mean that all of the threads report directly to the manager, and any
> >thread may create another thread _without_ communicating to the manager
> >(it just creates a new sibling).
>
> I like it.

I like it too. I'm doing it right now. Only problem is notifying the
parent that it had a child without knowing it! (Next on Jerry Springer..)

Semantics are basically this:

Any process created with the CLONE_PPIDOK flag is allowed to make children
for its parent. It can then be clone()d with CLONE_PPID, and do_fork()
will do the right thing wrt p_pptr and p_opptr.

outstanding issues:

1) send a signal to parent? SIG_NEWCHLD ? ick... but not notifying parent
is silly..

2) what if we ask for CLONE_PPID and CLONE_PPIDOK (which is copied into
task_struct flags as PF_PPIDOK) is not set? We can eitehr fail with EINVAL
(or better error?) or silently ignore CLONE_PPID. I opt for ignoring it
and clone()ing as usual.

any other thoughts?

Tim

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