Saving an image in a clean state is still a requirement, but I think
we can still achieve your vision, Eliot, by simply removing the
shutdown code of as many things as we can -- and take care their
things in their startup instead.

As we get more and more of them moved, shutDown: will run faster and
faster, and Save-and-Resume will be instantaneous.

This approach preserves backward compatibility and the requirement
that we be allowed to save-and-resume our images with a valid state.


On Mon, Apr 18, 2016 at 8:00 AM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> Hi Tim, Tobias & Marcel,
>
>> On Apr 18, 2016, at 12:47 AM, timfelgentreff <timfelgentreff at gmail.com> wrote:
>>
>> No, you need three variables. Your scenarios are correct, I think, but 1 and
>> 2 need to differentiate. If you're saving and quitting you want to compress
>> forms and remove tmpdirs and such, but if you're saving and keeping the
>> image open you want to skip the tmpdir removal, not close open sockets,
>> maybe only set a variable for startup to re-init that stuff...
>
> Ok so perhaps there are three states, but that doesn't imply three variables.  One would suffice if a symbol were used: #quit #save #saveAndQuit.
>
> But is it feasible to ignore #save and expect startUp: to deal with the deferred clean up?  #save is not, and usefully /should not/ be a shut down.  To exit the system, any save must be followed by either a #quit or a #saveAndQuit.  So IMO #save should not shutDown:.  Here are two motivating examples
>
> 1. Use of #save to produce a checkpoint, or produce an image to debug some issue at a later date.  In this case the image should be as close to the running image as possible.  Not shutting down in #save is required here.
>
> 2. Cleaning up C pointers.  It is common enough for applications to allocate external memory and refer to it through pointer objects (IIRC, Alien & ExternalAddress in Squeak et al, CPointer in VW).  These /cannot/ be released on #save, because doing so would force shutting down of external code that is using that memory.  So instead very early on startUp: all such referents are visited (eg via allInstances, or by enumerating a weak set) and their references are nilled (since the memory is released implicitly on #quit).
>
> So IMO #save should /not/ run either the shutdown list or the startup list in the saving image, and should only run the startup list in the new resuming image.
>
> This may require sophistication on behalf of the programmer, but the start up and shut down lists are indeed nontrivial things to program; they're often maintaining critical infrastructure such as the delay system, and total ordering is extremely important.  Good comments can help.
>
> If you look at VW, you'll see use of pragmas to provide better plug fabulist in terms of providing a priority for ordering, and IIRC for prerequisites.  We could consider a similar approach.
>
>
> _,,,^..^,,,_ (phone)
> Eliot
>
>> marcel.taeumel wrote
>>> Hi there,
>>>
>>> there are three different scenarios for shutdown:
>>>
>>> 1. Save and resume
>>> 2. Save and quit
>>> 3. Quit only
>>>
>>> For general clean-up routines, 1 and 2 should clean-up, while 3 does not
>>> have to. So, one variable might be sufficient. :-)
>>>
>>> Any other ways of using shutdown?
>>>
>>> Best,
>>> Marcel
>>
>>
>> --
>> View this message in context: http://forum.world.st/Why-do-we-process-the-shutdown-list-if-not-snapshotting-tp4890384p4890547.html
>> Sent from the Squeak - Dev mailing list archive at Nabble.com.
>>
>