[asterisk-bugs] [JIRA] (ASTERISK-21207) [patch] - Deadlock on fax extension calling ast_async_goto() with locked channel

[Ashley Winters (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-21207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=204532#comment-204532 ] 

Ashley Winters commented on ASTERISK-21207:
-------------------------------------------

Hijacking AST_CONTROL_T38_PARAMETERS isn't quite enough. The {{interpret_t38_parameters}} function queues a frame so {{ast_read}} can see it, but {{ast_read}} doesn't call {{tech->indicate}}. Since I'm venturing into uncharted territory anyways, I might as well try making {{ast_read}} call {{ast_indicate_data}} for AST_CONTROL_T38_PARAMETERS.
                
> [patch] - Deadlock on fax extension calling ast_async_goto() with locked channel
> --------------------------------------------------------------------------------
>
>                 Key: ASTERISK-21207
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-21207
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_dahdi, Channels/chan_sip/General
>    Affects Versions: 10.7.1, 11.2.1
>         Environment: CentOS 6.3 x86_64
>            Reporter: Ashley Winters
>            Severity: Critical
>         Attachments: fax-deadlock.patch, gdb-fax-deadlock.txt, t38-fax-deadlock.patch
>
>
> On an asterisk system with heavy use of AGI and inbound CNG-detected faxing, occasionally all channel activity will freeze. Running 'core show channels' returns nothing, but the logs continue running with anything except channel activity. Running with 'sip set debug on' shows that chan_sip.c doesn't even claim to be reading packets anymore.
> This deadlock was triggered several times daily across our array of asterisk servers, which process hundreds of faxes and tens of thousands of calls daily.

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