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Tight loop prevents other threads from running in available cores

    • Closed Issue created by Facundo Domínguez @facundominguez

    The following program does not terminate when compiled with: ghc --make -O -threaded test.hs and executed on linux on an amd64 machine with 16 cores with: ./test

    import Control.Concurrent
import Control.Monad
import System.Environment

main :: IO ()
main = do
  y <- getArgs
  mv0 <- newEmptyMVar
  mv1 <- newEmptyMVar
  forkIO $ do
    takeMVar mv0
    putMVar mv1 ()
    loop (y == ["yield"])
  putMVar mv0 ()
  takeMVar mv1
     >>= print

loop :: Bool -> IO ()
loop cooperative = go
  where
    go = when cooperative yield >> go

    Here [1] is the discussion about it so far.

    [1] http://www.haskell.org/pipermail/glasgow-haskell-users/2013-October/024412.html

    Trac metadata
    Trac field Value
    Version 7.6.3
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Runtime System
    Test case
    Differential revisions
    BlockedBy
    Related
    Blocking
    CC simonmar
    Operating system
    Architecture
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