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

[jrose]

> On Feb. 3, 2012, 12:35 p.m., Mark Michelson wrote:
> > /branches/1.8/channels/chan_agent.c, lines 405-406
> > <https://reviewboard.asterisk.org/r/1708/diff/5/?file=23882#file23882line405>
> >
> >     You also need to unlock owner in this if block.

*facepalm* That's embarrassing.


> On Feb. 3, 2012, 12:35 p.m., Mark Michelson wrote:
> > /branches/1.8/channels/chan_agent.c, lines 973-977
> > <https://reviewboard.asterisk.org/r/1708/diff/5/?file=23882#file23882line973>
> >
> >     You should copy p->moh into a local buffer while you have p locked.

Copied to char * with ast_strdupa.  This seems safe since ast_indicate_data copies the frame before it uses it... so I think the string that goes into the frame won't be freed.


> On Feb. 3, 2012, 12:35 p.m., Mark Michelson wrote:
> > /branches/1.8/channels/chan_agent.c, line 1657
> > <https://reviewboard.asterisk.org/r/1708/diff/5/?file=23882#file23882line1657>
> >
> >     This should be "owner = agent_lock_all(p);"

And another fail. Thanks for catching it.


> On Feb. 3, 2012, 12:35 p.m., Mark Michelson wrote:
> > /branches/1.8/channels/chan_agent.c, line 1804
> > <https://reviewboard.asterisk.org/r/1708/diff/5/?file=23882#file23882line1804>
> >
> >     This should be "owner = agent_lock_all(p);"

These probably came from when I was thinking about just using the p->owner instead of the actual owners... but then I must have forgotten to change them back.


- jrose


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On Feb. 3, 2012, 11:52 a.m., jrose wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/1708/
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> 
> (Updated Feb. 3, 2012, 11:52 a.m.)
> 
> 
> Review request for Asterisk Developers, Mark Michelson, rmudgett, and Matt Jordan.
> 
> 
> Summary
> -------
> 
> 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
> 
> 
> Diffs
> -----
> 
>   /branches/1.8/channels/chan_agent.c 353685 
> 
> Diff: https://reviewboard.asterisk.org/r/1708/diff
> 
> 
> Testing
> -------
> 
> 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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