[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=205359#comment-205359 ] 

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

The {{ast_channel_unlock}} in {{process_sdp}} was just cut&pasted into place, and is pointless. It only unlocks the recursive lock from a couple lines up, not the big lock held by the caller of {{process_sdp}} -- ultimately {{handle_request_do}}.
                
> [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: backtrace-threads.txt, core-show-locks.txt, fax-deadlock.patch, fax-deadlock-v2.patch, fax-deadlock-v2.patch-11.3.0, gdb-fax-deadlock.txt, issue_log
>
>
> 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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