[asterisk-bugs] [JIRA] (ASTERISK-22976) app_queue function queue_show() and find_queue_by_name_rt() cause deadlock

[Aaron An (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-22976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=240789#comment-240789 ] 

Aaron An commented on ASTERISK-22976:
-------------------------------------

hi, Joshua Colp, I don't use app_queue any more for past 2 years, so I don't know whether it is resolved or not in recent version. But I guess the dead lock is remain there especially using realtime queue. Realtime have I/O outside so the rate of race condition will larger than static queue. 

> app_queue function queue_show() and find_queue_by_name_rt() cause deadlock 
> ---------------------------------------------------------------------------
>
>                 Key: ASTERISK-22976
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-22976
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Applications/app_queue
>    Affects Versions: 1.8.24.0
>         Environment: CentOS5.8 X64 DellR410 Asterisk 1.8 trunk version
>            Reporter: Aaron An
>            Assignee: Aaron An
>            Severity: Critical
>
> I use "queue show xxxx" to monitor queue status, and use realtime queue. concurrency is about 100 calls. deadlock will be occur after 10-30minutes.
> analysis result：
> in find_queue_by_name_rt() first lock single queue "ao2_lock(q);" and then lock global queues "queues_t_unlink(queues, q, "Unused; removing from container");";
> in __queues_show() first lock global queues "ao2_lock(queues);" then lock single queue "ao2_lock(q);"
> so it causes dead lock.



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