[GHC] #5773: main = forever (putStrLn =<< getLine) continuously saturates a CPU when compiled

[GHC]

#5773: main = forever (putStrLn =<< getLine)   continuously saturates a CPU when
compiled
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 Reporter:  lpsmith                  |          Owner:                
     Type:  bug                      |         Status:  new           
 Priority:  normal                   |      Component:  Compiler      
  Version:  7.4.1-rc1                |       Keywords:                
       Os:  Linux                    |   Architecture:  x86_64 (amd64)
  Failure:  Runtime performance bug  |       Testcase:                
Blockedby:                           |       Blocking:                
  Related:                           |  
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Comment(by lpsmith):

 Playing around with this issue a little bit more,  {{{getLine}}} and
 {{{hGet}}} from {{{Data.ByteString.Char8}}} also saturate the CPU when
 they block.   However I do have some code that uses {{{threadWaitRead}}}
 and a C library to fetch some input (specifically, the asynchronous
 notification mechanism of PostgreSQL via libpq),  which does not exhibit
 this problem.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5773#comment:2>
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