Re: Children of dead processes

Philipp, Bishnupriya,

Indeed. An implementation may choose to invalidate any process handles as
soon as a process instance terminates. In the case of a terminated process
with children, we have to decide whether the implementation is obliged to
keep any process handles valid as long as the process object continues to
exists. Otherwise we may have the situation where there exists a
non-terminated child process whose parent process continues to exist but
has an invalid handle. I do not see this is a problem, but it does seem a
little odd.

John A

From:
"Philipp A. Hartmann" <philipp.hartmann@offis.de>
To:
john.aynsley@doulos.com
Cc:
Bishnupriya Bhattacharya <bpriya@cadence.com>,
"systemc-p1666-technical@eda.org" <systemc-p1666-technical@eda.org>
Date:
12/01/2011 14:53
Subject:
Re: Children of dead processes

Yes, exactly.

Additionally, this has implications for the invalidation of process
handles as well, right?

Philipp

On 12/01/11 13:49, john.aynsley@doulos.com wrote:
> 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
>
>
>
>

-- 
Philipp A. Hartmann
Hardware/Software Design Methodology Group
OFFIS Institute for Information Technology
R&D Division Transportation · FuE-Bereich Verkehr
Escherweg 2 · 26121 Oldenburg · Germany · http://offis.de/en/
Phone/Fax: +49-441-9722-420/282 · PGP: 0x9161A5C0 · Skype: phi.har
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