[asterisk-dev] [Code Review] Fix deadlock between subscription event RWLOCK and dialogs container lock in chan_sip.

schmidts reviewboard at asterisk.org
Thu Nov 3 04:03:59 CDT 2011


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i dont get now why are you changing the callid but except this it looks good so far.


/branches/1.8/channels/chan_sip.c
<https://reviewboard.asterisk.org/r/1557/#comment8849>

    i had this in my original patch but i am not sure if we shouldnt let this checks for an active audio or video bridge stay in here.
    
    


- schmidts


On Nov. 2, 2011, 8:25 p.m., rmudgett wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
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> (Updated Nov. 2, 2011, 8:25 p.m.)
> 
> 
> Review request for Asterisk Developers and David Vossel.
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> 
> Summary
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> Timing between dialog destruction and a MWI event sending a message could result in a deadlock.
> 
> Order of events causing deadlock:
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> 1a) The event subscription system calls the registered callbacks with its list RWLOCK held.
> 1b) The SIP monitor checks for dialogs needing destruction.  It does an ao2_callback that holds the dialogs container lock while searching for dialogs to destroy.
> 2a) The event subscription SIP callback needs to create a temporary dialog to send out the MWI notification.  That temporary dialog needs to be inserted in the dialogs container so it must wait.
> 2b) The dialog search finds a dialog to destroy and as a result releases the last reference for a peer.  The peer destructor attempts to get the subscription RWLOCK but must wait.
> 3) deadlock
> 
> 
> This addresses bug ASTERISK-18747.
>     https://issues.asterisk.org/jira/browse/ASTERISK-18747
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> 
> Diffs
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>   /branches/1.8/channels/chan_sip.c 343275 
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> Diff: https://reviewboard.asterisk.org/r/1557/diff
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> 
> Testing
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> It compiles. :)
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> 
> Thanks,
> 
> rmudgett
> 
>

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