[asterisk-dev] [Code Review] Dialplan function for manager account checks - AMI_CLIENT()

[Mark Michelson]

> On 2010-07-28 10:48:04, Tilghman Lesher wrote:
> > /trunk/main/manager.c, lines 6068-6077
> > <https://reviewboard.asterisk.org/r/421/diff/3/?file=11951#file11951line6068>
> >
> >     btw, there's a good reason to implement this as a callback.  There's a possible race condition here that could make this function return the wrong value:
> >     
> >     1. Lock container.
> >     2. Store container version.
> >     3. Unlock container.
> >     LOOP:
> >     4. Lock container.
> >     5. Compare container version.  If changed, restart loop.  Else get next item in container.
> >     6. Unlock container.
> >     7. Return item.
> >     8. Increment no_sessions.
> >     9. Goto LOOP.
> >     
> >     If the container version changes, which occurs each time that an item is either added to or removed from the container, then the loop could be restarted, which isn't a big deal, if you are, for example, comparing values (it just takes slightly longer), but it's a very big deal if you're incrementing a monotonically incrementing integer, whose value is the entire point of the function.  Each time the container is unlocked, there's a potential for an item to be added or removed from the container at that time.
> 
> Olle E Johansson wrote:
>     Does code like this exist anywhere? I need some examples.

One example would be in trunk/main/ccss.c, ast_cc_monitor_count(). This function uses ao2_t_callback() to visit each member of a container, and increment a counter under the correct circumstances. The code listed here seems to be a similar operation.


- Mark


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On 2010-07-28 04:20:49, Olle E Johansson wrote:
> 
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> https://reviewboard.asterisk.org/r/421/
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> 
> (Updated 2010-07-28 04:20:49)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Summary
> -------
> 
> Implementation of a dialplan function for checking manager accounts. I've made it extensible so that we can add other parameters when needed. Right now it only checks the number of logged in sessions for a manager account.
> 
> 
> Diffs
> -----
> 
>   /trunk/main/manager.c 280055 
> 
> Diff: https://reviewboard.asterisk.org/r/421/diff
> 
> 
> Testing
> -------
> 
> Tested on my Linux system and it reports manager logins properly - 0, 1 and 2 concurrent sessions...
> 
> 
> Thanks,
> 
> Olle E
> 
>