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

On Tue, Apr 9, 2013 at 7:07 PM, Pawel <[hidden]> wrote:

>
> - port is inactive - ?? Client suppose that port exits - and it exists, so
> it's "broken" ... but because jack server KNOW this before serve it to
> client  - it should at least try to avoid problems.
>
> What I want to say - we can't fix this ultimately - but jack server should
> at least TRY to protect client from evil


you can't protect them from *all* "evil", so the question is : which types
of "evil" will we attempt to avoid.


> - and in this case he definitely can. So , once again - jack_get_ports
> shouldn't return broken ports if he know they are useless for client.
>

mostly agreed.


>
> I also can't find a problem in jack_is_port_active. Example:
> jack_get_ports(....)
> <--- obviously some time here - and things can change ..
> jack_port_t* port = jack_get_port_by_name ( ...)
> <-- still things can change - but if we got port == NULL we fail here and
> remove port from patchbay graph.
> jack_port_is_active ( client, port);
>
# return 0 on success i.e. port still exists and is active. Otherwise we
> can return some codes like "1 - not active, 2 - not exists .. etc, but for
> me (as patch manager maintainer) it's clear that in this short time window
> port is broken. I just mark it as "unusable" .. and wait for another event.
>

so for now, you know that the port is active ... so what? you can't do
anything useful with this information.

every time you use jack_get_ports(), you get, as you noted above, a
"snapshot" of things. there is no way to prolong the life of the
information in the snapshot. when you come to use the information, you
*must* be ready for some or all of it to be invalid or out of date.

i think this is a somewhat separate question to whether or not we should
return ports that *at the time of jack_get_ports()* are known to be
inactive. logic and cleanliness would suggest that we should not. however,
the comparison with other kinds of potential "invalidation" of port
information says "it doesn't really matter".

--p

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