Merged revisions 334010 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/10

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  r334010 | rmudgett | 2011-08-31 10:23:11 -0500 (Wed, 31 Aug 2011) | 50 lines
  
  Merged revisions 334009 via svnmerge from 
  https://origsvn.digium.com/svn/asterisk/branches/1.8
  
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    r334009 | rmudgett | 2011-08-31 10:20:31 -0500 (Wed, 31 Aug 2011) | 43 lines
    
    Call pickup race leaves orphaned channels or crashes.
    
    Multiple users attempting to pickup a call that has been forked to
    multiple extensions either crashes or fails a masquerade with a "bad
    things may happen" message.
    
    This is the scenario that is causing all the grief:
    1) Pickup target is selected
    2) target is marked as being picked up in ast_do_pickup()
    3) target is unlocked by ast_do_pickup()
    4) app dial or queue gets a chance to hang up losing calls and calls
    ast_hangup() on target
    5) SINCE A MASQUERADE HAS NOT BEEN SETUP YET BY ast_do_pickup() with
    ast_channel_masquerade(), ast_hangup() completes successfully and the
    channel is no longer in the channels container.
    6) ast_do_pickup() then calls ast_channel_masquerade() to schedule the
    masquerade on the dead channel.
    7) ast_do_pickup() then calls ast_do_masquerade() on the dead channel
    8) bad things happen while doing the masquerade and in the process
    ast_do_masquerade() puts the dead channel back into the channels container
    9) The "orphaned" channel is visible in the channels list if a crash does
    not happen.
    
    This patch does the following:
    
    * Made ast_hangup() set AST_FLAG_ZOMBIE on a successfully hung-up channel
    and not release the channel lock until that has happened.
    
    * Made __ast_channel_masquerade() not setup a masquerade if either channel
    has AST_FLAG_ZOMBIE set.
    
    * Fix chan_agent misuse of AST_FLAG_ZOMBIE since it would no longer work.
    
    (closes issue ASTERISK-18222)
    Reported by: Alec Davis
    Tested by: rmudgett, Alec Davis, irroot, Karsten Wemheuer
    
    (closes issue ASTERISK-18273)
    Reported by: Karsten Wemheuer
    Tested by: rmudgett, Alec Davis, irroot, Karsten Wemheuer
    
    Review: https://reviewboard.asterisk.org/r/1400/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@334011 65c4cc65-6c06-0410-ace0-fbb531ad65f3