[asterisk-bugs] [JIRA] (ASTERISK-24822) Deadlock: Fax Gateway framehook creates locking inversion in T.38 query option with features bridging code

[Matt Jordan (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-24822?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=225075#comment-225075 ] 

Matt Jordan commented on ASTERISK-24822:
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It'd be a relatively rare locking inversion, but it can happen.

In the fax framehook, we have channel {{0x9999a20}} locked. That's normal in an {{ast_indicate_data}} callback. The framehook calls {{ast_channel_get_t38_state}}, which calls {{ast_channel_queryoption}} on another channel - in this case {{0x9c63830}}.

Meanwhile, {{app_dial}} has indicated to data to {{0x9c63830}}, which causes it to reach across its bridge to indicate a source update to {{0x9999a20}}. This is okay, except that {{0x9999a20}} is currently locked by the fax framehook.

> Deadlock: Fax Gateway framehook creates locking inversion in T.38 query option with features bridging code
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: ASTERISK-24822
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24822
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/General
>    Affects Versions: 11.14.2
>         Environment: CentOS5 64bit
>            Reporter: David Brillert
>         Attachments: CodeShowLocks.txt, DebugOutput.txt
>
>
> Asterisk locks, no output from sip CLI commands during lock.
> core show locks attached
> gdb thread apply all bt attached
> Don't know how to reproduce...



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