[GHC] #7787: modifyMVar does not restore value if callback returns error value

[GHC]

#7787: modifyMVar does not restore value if callback returns error value
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    Reporter:  joeyadams         |       Owner:                             
        Type:  bug               |      Status:  new                        
    Priority:  high              |   Milestone:  7.8.1                      
   Component:  libraries/base    |     Version:  7.7                        
    Keywords:                    |          Os:  Unknown/Multiple           
Architecture:  Unknown/Multiple  |     Failure:  Incorrect result at runtime
  Difficulty:  Unknown           |    Testcase:                             
   Blockedby:                    |    Blocking:                             
     Related:                    |  
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Changes (by igloo):

  * priority:  normal => high
  * difficulty:  => Unknown
  * milestone:  => 7.8.1


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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7787#comment:3>
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