Another finalization concern: error handling

>
>
> On Mon, Oct 11, 2010 at 3:07 PM, Igor Stasenko <[hidden email]> wrote:
>>
>> On 12 October 2010 00:02, Eliot Miranda <[hidden email]> wrote:
>> > Igor,
>> >     take a look at the VisualWorks finalization code.  There a process
>> > is
>> > spawned to run each finalizer, and there is a throttling mechanism to
>> > ensure
>> > that the system does not create a flood of processes when lots of
>> > objects
>> > are to be finalized.  Instead, a new finalization process is created
>> > only
>> > when the previous one starts to run.  A new finalizer process is created
>> > when the previous one starts because, due to errors, the previous one
>> > may
>> > never finish, but it will always start.
>>
>> This is a little bit confusing. Did you mean:
>>
>> new finalization process is created only when the previous one _stops_ to
>> run
>
> No.  The top-level loop spawns processes at a lower priority to run
> finalization; I'll call these sub-processes.  If one creates a sub-process
> as soon as an object is available to finalize then the system can end up
> creating many many sub-processes, none of which can run since the top-level
> process is busy creating sub-processes.  If one creates a sub-process only
> when a previous sub-process terminates then the system is no different to
> now; if an error occurs in a sub-process taht prevents it teminating then no
> more sub-processes are created and finalization stops.
> If instead one creates a new sub-process when a previous sub-process starts
> executing (starts executing is not the same point in time as create the
> process) then there are only ever two subprocesses, the one already running,
> and the one that was created when the first started running, but has not
> started running since cooperative scheduling means it is queued behind the
> previous sub-proecss.  However, as soon as an error occurs in the previous
> sub-process, the one that was created when the sub-process with the error
> started will start running and create another one.
> Read the VisualWorks source code and it will, I hope, become clear.