[GHC] #6041: Program hangs when run under Ubuntu Precise

[GHC]

#6041: Program hangs when run under Ubuntu Precise
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 Reporter:  dsf            |          Owner:                  
     Type:  bug            |         Status:  new             
 Priority:  normal         |      Component:  Compiler        
  Version:  7.4.1          |       Keywords:                  
       Os:  Linux          |   Architecture:  Unknown/Multiple
  Failure:  Runtime crash  |       Testcase:                  
Blockedby:                 |       Blocking:                  
  Related:                 |  
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 This code hangs when running under Ubuntu Precise. However, it works in a
 Precise changeroot on an Ubuntu Lucid machine -- indicating it could be
 kernel specific.  My guess would be that it would succeed on a Precise
 machine running a Lucid kernel, but we have not tried that.

 Any of the following changes make the code work:

  1. replacing 'readTVar u' with 'return ()'
  2. removing the 'Wrapper' monad and just using 'StateT'
  3. deriving the 'MonadState' instance instead of righting it by hand
  4. copying the definition of 'modify' into the local module and use that
 instead of the imported version

 The final mystery: If the binary is built in a precise changeroot (where
 it works) and then copied to a precise machine ... it still works.  And if
 it is built on a real precise machine, where it fails, it still fails when
 copied to a precise changeroot on a lucid machine.

 So, there's that.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6041>
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