[asterisk-dev] [Code Review] 2721: bridge_channels: Add support for the lonely flag

[David Lee]

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/trunk/main/bridge_channel.c
<https://reviewboard.asterisk.org/r/2721/#comment18291>

    This loop works in O(n) every time a channel is removed from a bridge. But since all n channels will eventually be removed from the bridge, this loop will have an effective cost of O(n^2) removing all channels from a bridge. For even a moderate number of channels in a bridge, this could be a big performance problem.
    
    It may be better to count lonely channels as they are added/removed from the bridge, assuming that a channel can't become lonely/unlonely once it's in a bridge.



/trunk/main/bridge_channel.c
<https://reviewboard.asterisk.org/r/2721/#comment18288>

    bridge_channel_internal_pull() and bridge_channel_dissolve_check() are co-recursive. The code might actually work, just accidentally.
    
    The internal_pull() function removes other from bridge->channels, which causes the loop to terminate early. The loop only pulls the first channel from the bridge.
    
    But since internal_pull() calls dissolve_check(), it will recursively pull the first channel from the bridge until all the channels have been removed.
    
    With enough lonely channels in a bridge, this could blow the stack.


- David Lee


On July 31, 2013, 12:31 p.m., jrose wrote:
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> This is an automatically generated e-mail. To reply, visit:
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> (Updated July 31, 2013, 12:31 p.m.)
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> 
> Review request for Asterisk Developers, David Lee, Matt Jordan, and rmudgett.
> 
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> Bugs: ASTERISK-22117
>     https://issues.asterisk.org/jira/browse/ASTERISK-22117
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> Repository: Asterisk
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> Description
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> Channels with the lonely flag are supposed to leave a bridge if all of the channels in that bridge are also lonely at the time of a channel dissolving.
> I also added this flag to ARI play and record on bridge channels.
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> Diffs
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>   /trunk/main/core_unreal.c 395852 
>   /trunk/res/ari/resource_bridges.c 395852 
>   /trunk/include/asterisk/core_unreal.h 395852 
>   /trunk/main/bridge_channel.c 395852 
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> Diff: https://reviewboard.asterisk.org/r/2721/diff/
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> Testing
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> Tested what happens to channels when a non-lonely channel leaves with and without the presence of non-lonely channels.
> If only lonely channels were left, they hung up. This did produce an ARI playback error since the channel playback was interrupted.
> If non-lonely channels were left, nothing would happen as anticipated.
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> Thanks,
> 
> jrose
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>

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