https://origsvn.digium.com/svn/asterisk/branches/1.8

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  r314067 | dvossel | 2011-04-18 10:23:45 -0500 (Mon, 18 Apr 2011) | 22 lines
  
  Remove the need for deadlock avoidance in chan_sip do_monitor.
  
  Deadlock avoidance between the sip pvt and the pvt->owner is
  very difficult.  Now that channel's are ao2 objects, this complication
  is no longer necessary.  It turns out the pvt's msg queue only
  exists because of deadlock avoidance (when deadlock avoidance fails
  msgs were added to a queue to be processed later), so this goes away as well.
  
  The technique used in the new sip_lock_pvt_full() function should
  be used as a template for replacing all locations where deadlock
  avoidance occurs between a channel tech_pvt and the pvt's owner.
  My hope is that this will begin a reversal of the invalid channel
  driver locking architecture we have been using for so long. 
  
  This patch also resolves an issue where the pvt->owner gets
  unlocked during processing the msg queue.
  
  (closes issue #18690)
  Reported by: dvossel
  
  Review: https://reviewboard.asterisk.org/r/1182/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@314078 65c4cc65-6c06-0410-ace0-fbb531ad65f3