[GHC] #4504: "awaitSignal Nothing" does not block thread with -threaded

[GHC]

#4504: "awaitSignal Nothing" does not block thread with -threaded
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  Reporter:  adept                        |          Owner:  adept           
      Type:  bug                          |         Status:  closed          
  Priority:  normal                       |      Milestone:  7.2.1           
 Component:  Runtime System               |        Version:  7.0.1           
Resolution:  fixed                        |       Keywords:                  
  Testcase:                               |      Blockedby:                  
Difficulty:                               |             Os:  Unknown/Multiple
  Blocking:                               |   Architecture:  Unknown/Multiple
   Failure:  Incorrect result at runtime  |  
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Comment(by kazu-yamamoto):

 If this patch does not break anything, please include to 7.0.2. According
 to adept, this patch is necessary to run the "c10k" package well.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4504#comment:17>
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