Re: [PATCH] setsid: don't fork

[Phillip Susi <psusi@ubuntu.com>]

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On 11/19/2013 1:05 PM, Karel Zak wrote:
> but why you don't want --wait behavior? It does not change
> anything, but fix the problem with group leader.

I *do* want that behavior, I just think it was supposed to have been
that way all along and which behavior you get should NOT depend on
whether it is a group leader or not.

> IMHO we can make it (--wait) the default (you almost convinced me 
> that the default behaviour should be fixed).

Why even have the option then?  Does anyone actually want the non wait
behavior?  If they have to add a switch to get it, they may as well
just have the shell background the job.  Simpler and cleaner than a
switch.

> fork for sleep() and then kill it

Why is that worse than fork then exec?  And I thought swapping the
group leader so the parent process can call setsid() was pretty clever ;)

> I'm also not sure if remove --wait is the best way... what about 
> people who already use it? (yep, it's release few weeks ago,
> but...)

The longer it stays in, the more people will use it.  Best to get rid
of it now if it wasn't such a great idea, otherwise it will be there
forever.

> If I good understand the man page then setsid() caller is session
> and group leader of the *new* session and group. It's probably
> unwanted to make the original group orphaned (without leader),
> because processes in orphaned group get SIGCONT from kernel...
> 
> (BTW, SIGCONT is probably what will happen in your version after 
> kill(pid) as the sleeping child is group leader, right?)

I think that happens the old way too: as soon as setsid exits after
successfully forking the child, then the group is orphaned.  In other
words, both setpgrp() and exit() remove this process from being the
group leader.

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