[asterisk-dev] [Code Review] Implement ast_channel_search_locked to expensive per-notify channel walk in chan_sip

[Brian Degenhardt]

Sean Bright wrote:
> Brian Degenhardt wrote:
>> Russell, at astridevcon we talked about CEL's method of seeing if a
>> linkedid exists when a channel is destroyed, and how it needs to search
>> all channels.  Would this be a reasonable substitute to accomplish that
>> task?
>> 
>> Murf was going to do the whole hashtab thing, but this might be good enough.
>> 
>> What do you guys think?  Here's the current function, to refresh your
>> memory:
> 
> You should be able to re-write it like this:
> 
> /* called whenever a channel is destroyed or a linkedid is changed to
> potentially emit a CEL_LINKEDID_END event */
> void ast_cel_check_retire_linkedid(const struct ast_channel *chan)
> {
>     auto int linkedid_match(struct ast_channel *c);
>     int linkedid_match(struct ast_channel *c) {
>         return (c != chan && c->linkedid && !strcmp(linkedid, c->linkedid));
>     }
>     const char *linkedid = chan->linkedid;
> 
>     /* make sure we need to do all this work */
>     if (!ast_strlen_zero(linkedid) && track_event(CEL_LINKEDID_END)) {
> 	struct ast_channel *tmp = NULL;
>         if ((tmp = ast_channel_search_locked(linkedid_match))) {
>             ast_channel_unlock(tmp);
>             tmp = NULL;
>         } else {
>             ast_cel_report_event(chan, CEL_LINKEDID_END, NULL, NULL, NULL);
>         }
>     }
> }
> 
> And you're good to go.
> 

That's what I was thinking, but I was wondering if Murf and Russell
could comment on if that approach is adequate, or if we want to maintain
a hashtab of channels keyed on linkedid, and insert/remove them from there.

I'm sorta partial to your way, above.  While it's slower, we don't have
to worry about maintaining the separate data structure which has the
potential to get out of sync.  Especially since this code only runs if
you care about LINKEDID_END events.

cheers
-bmd