On Mon, Feb 22, 2016 at 12:30 PM, Volker Braun <[email protected]> wrote:
> Every interfaces tries to launch the sage-cleaner. If it is already running,
> the newly-forked sage-cleaner quits immediately. But there is nobody reaping
> the child, so a zombie remains.
>
> The standard solutions are either
> 1) waitpid in the parent e.g. whenever a new interface is created,
> 2) double fork, then the sage-cleaner would be the grandchild adopted by
> init
> 3) SIGCHLD signal handler, which complicates further fork()s of sage
>
>
> On Monday, February 22, 2016 at 8:27:55 PM UTC+1, William wrote:
>>
>> It depends on how Sage exits.  If it exists properly then yes, they
>> are killed.  But Sage could exit by being "kill -9'" or by segfaulting
>> or something else.  Even then, it is important for the things Sage
>> spawned to be killed.
>
>
> IMHO an overall better design would be to have a monitor process for every
> spawned sub-process instead of sage-cleaner being responsible for processes

I agree.  That's more how the "forever" monitor works in the world of
node.js.  It would be great if sage-cleaner were finally replaced.  It
was just a quick hack I wrote for an admin on a cluster somewhere in
2006, who were complaining that their users were leaving around sage
zombie processes.  I also don't know to what (if any) extent the once
working-well-enough sage-cleaner got broken by subsequent code.

> that are not its direct children. The current solution is definitely racy if
> there is pid wraparound.
>
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-- 
William (http://wstein.org)

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