Re: [Jack-Devel] Graph callback and client state

On Tue, 2013-04-09 at 15:51 -0400, Paul Davis wrote:
> 
> 
> On Tue, Apr 9, 2013 at 3:33 PM, Harry van Haaren
> <[hidden]> wrote:
>         On Tue, Apr 9, 2013 at 7:45 PM, Stéphane Letz <[hidden]>
>         wrote:
>         > You can never be sure that ports returned by jack_get_ports
>         are always valid
>         
>         
>         
>         Any chance that adding a flag,  "JackPortIsActive" to
>         JackPortFlags allows the functionality to be implemented?
>         
>         On activation, the JACK server marks all of the client owned
>         ports as "active".
>         
>         Patchbay managers etc call jack_port_flags() and can query if
>         its an "active" port or not?
>         
> 
> there is always a race ... sometime between when you get the ports and
> when you use the information, ports could be added, removed or become
> inactive.

Of course its possible that the port is removed in the mean time. In
that case there is absolutely no problem because there is no need to
care about a non-existent port because you can't (dis)connect it anyway.

This 'problem' manifests in vastly more complex connection management
code, as connection managers have to additionally monitor that their
connection attempt worked and may have to repeatedly retry making the
connection later because it still may not be active yet.

If inactive ports are not listed then connection managers may simply
fire & forget the connect request. If the port no longer exists, so
what, it can't be connected anyway.

Of course making this change doesn't fix all problems, but it does help
one. Surely that's an advantage? 

1365590789.16079_0.ltw:2,a <1365590780.3777.3057.camel at petern dot bnsnet dot co dot uk>