RE: Children of dead processes

Bishnupriya, Philipp,

Agreed. So as I understand it, we are proposing that for every occurrence
of get_parent_object() in the LRM, we change the description to say that
the following:

If the parent object is a process instance and that process has
terminated, get_parent_object shall return a pointer to the process
instance. The parent process instance shall not be deleted while the
process instance has child objects, but may be deleted once all its child
objects have been deleted

Right?

John A

From:
Bishnupriya Bhattacharya <bpriya@cadence.com>
To:
"john.aynsley@doulos.com" <john.aynsley@doulos.com>,
"philipp.hartmann@offis.de" <philipp.hartmann@offis.de>,
"systemc-p1666-technical@eda.org" <systemc-p1666-technical@eda.org>
Date:
11/01/2011 18:14
Subject:
RE: Children of dead processes

John,
 
Philip raises excellent questions, and I?m very much in favor of mandating
that parent process objects with live children should not be deleted. It
provides a nice, clean, intuitive semantics with no ?surprises? for the
user.
 
Thanks,
-Bishnupriya
 
From: john.aynsley@doulos.com [mailto:john.aynsley@doulos.com]
Sent: Tuesday, January 11, 2011 6:04 PM
To: Bishnupriya Bhattacharya; philipp.hartmann@offis.de;
systemc-p1666-technical@eda.org
Subject: Children of dead processes
 
All,

Philipp has raised the following issues:

6.6.5 sc_process_handle::get_parent_object
6.16.7 sc_object::get_parent_object

  "If the parent object is a process instance and that process has
terminated, get_parent_object shall return either a pointer to the
surviving process instance or a null pointer if it has been deleted."

 What happens to the object's position itself, when the parent object is
NULL?

   - It can still be found via sc_find_object( obj.name() )?

   - Is it moved to the top-level, i.e. can it be found via
sc_get_top_level_objects()?

   - But then basename() != name(), but (since no parent)
     get_parent_object()->name() '.' basename() != name()
     (The name can't be changed, since it is meant to stay valid until the
object is deleted?)

 This may affect sc_event naming as well.

6.16.1 sc_object Description (see get_parent_object above)

  "... objects of a class derived from sc_object may be deleted at any
time. When such an sc_object is deleted, it ceases to be a child."

  If it has child objects itself (in case of a process), what happens to
their position in the hierarchy? And their names?

  I would even prefer to have a restriction that in case, the "parent"
object shall not be deleted/invalidated until all children have been
deleted. But this might break "early invalidating" implementations.

[JA] We have already agreed that dynamic processes may be terminated while
they still have children, in which case a call to get_parent_object() for
any orphaned objects returns a null pointer. On the other hand, insisting
that parent process objects cannot be deleted while they have surviving
children would be a clean solution.

Opinions?

John A

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