Re: [Boost-bugs] [Boost C++ Libraries] #5516: Upgrade lock is not acquired when previous upgrade lock releases if another read lock is present

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5516: Upgrade lock is not acquired when previous upgrade lock releases if another read lock is present
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-12-07 17:59:05

#5516: Upgrade lock is not acquired when previous upgrade lock releases if another
read lock is present
------------------------------------+---------------------------------------
  Reporter:  fred@…                 |       Owner:  viboes  
      Type:  Bugs                   |      Status:  assigned
 Milestone:  To Be Determined       |   Component:  thread  
   Version:  Boost 1.42.0           |    Severity:  Problem 
Resolution:                         |    Keywords:          
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Changes (by viboes):

 * cc: viboes (added)
  * owner:  anthonyw => viboes
  * status:  new => assigned

Comment:

 It seems to me that this is by definition of the provided feature.

 From the documentation:
 "This is an extension to the multiple-reader / single-write model provided
 by the SharedLockable concept: a single thread may have upgradable
 ownership at the same time as others have shared ownership. The thread
 with upgradable ownership may at any time attempt to upgrade that
 ownership to exclusive ownership. If no other threads have shared
 ownership, the upgrade is completed immediately, and the thread now has
 exclusive ownership, which must be relinquished by a call to unlock(),
 just as if it had been acquired by a call to lock().

 If a thread with upgradable ownership tries to upgrade whilst other
 threads have shared ownership, the attempt will fail and the thread will
 block until exclusive ownership can be acquired.
 "
 Of course the implementation could give priority to writers, but this
 should be implemented in another class.

 What is then wrong?

 Moved to Support request until resolution clarified.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5516#comment:2>
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