[asterisk-bugs] [JIRA] (ASTERISK-22749) Deadlock during 4-way conference creation

[Kinsey Moore (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-22749?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kinsey Moore updated ASTERISK-22749:
------------------------------------

    Attachment: lock_inversion.diff
    
> Deadlock during 4-way conference creation
> -----------------------------------------
>
>                 Key: ASTERISK-22749
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-22749
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Bridges/bridge_native_rtp
>    Affects Versions: 12.0.0-beta1
>         Environment: 4 sip phones configured for res_pjsip with direct_media=yes and extensions to be able to dial the other phones to build the conference via DTMF attended transfer
>            Reporter: Kinsey Moore
>         Attachments: lock_inversion.diff
>
>
> When adding channels via DTMF attended transfer to get to a 4-way bridge, lock inversion is encountered causing a 4-way deadlock. This is a result of the update_peer RTP glue callback for chan_pjsip attempting to lock the bridge while the channel is obligatorily locked. This is worked around by the attached patch, but it exposed other issues.
> Beyond the fixes the patch provides, there is still one outstanding issue that needs to be resolved: the bridge_start and bridge_stop native RTP functions are called while a non-unlockable channel lock is held due to being called in a framehook callback. This is an issue because the bridge MUST be locked before calling the bridge_stop or bridge_start functions and results in a forced lock inversion.

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