[asterisk-dev] [Code Review] Fix a deadlock in agents occuring due to trying to lock a channel while having a lock on the pvt.

[rmudgett]

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/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9920>

    Potential deadlock trying to grab two channel locks in ast_read().



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9921>

    Potential use of new locking method.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9917>

    Should not have private lock held here because of potential deadlock with channel locks.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9916>

    Holding chan lock while calling ast_indicate_data() *will* cause a deadlock if it is a local channel.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9918>

    Should use owner instead of p->owner after you grabbed the owner lock.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9919>

    Ooh look an opportunity to use the new locking method.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9914>

    Owner lock and ref not released here.



/branches/1.8/channels/chan_agent.c
<https://reviewboard.asterisk.org/r/1708/#comment9915>

    Owner lock and ref not released here.


- rmudgett


On Feb. 1, 2012, 2:20 p.m., jrose wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
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> (Updated Feb. 1, 2012, 2:20 p.m.)
> 
> 
> Review request for Asterisk Developers, Mark Michelson, rmudgett, and Matt Jordan.
> 
> 
> Summary
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> Also adds locking to a number of other functions which are calling ast_bridged_channel (which is documented as requiring a lock for safe running, which was the purpose of irroot's original locking patch in action_agents.
> 
> Unlike the other patch on reviewboard right now, this opts to enforce locking order instead of using deadlock avoidance.
> 
> Celebrity endorsement: "This looks incredibly sane to me." - MMichelson
> 
> 
> This addresses bug ASTERISK-19285.
>     https://issues.asterisk.org/jira/browse/ASTERISK-19285
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> 
> Diffs
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>   /branches/1.8/channels/chan_agent.c 353685 
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> Diff: https://reviewboard.asterisk.org/r/1708/diff
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> 
> Testing
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> Not much I'm afraid to say. I can't reproduce the issue since it involves real world use over a period of time.  I'll ask Alex Villacís Lasso to give it a shot though.
> 
> 
> Thanks,
> 
> jrose
> 
>

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