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  • Glasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #352

Closed
Open
Opened Apr 15, 2005 by nobody@trac-nobody

Possible error using concurrency

{- 
     Error description:

     In windows xp sp2 with ghc-6-4, GHCi ends with 
        "internal error: deadlock: main thread blocked in a 
strange way"
     In RedHat Linux, it just blocks.
     A probably cause, it's that the scheduler hasn't yet 
run oneThread
     before the second putTMVAr, because no memory 
allocation has been
     requested.
     Try on the calls forkIO and runInUnboundThread.

     contact info: leonelfl@yahoo.com
-}
import Control.Concurrent
import Control.Concurrent.STM
import Control.Concurrent.STM.TMVar
main = do
   stopFlag <- atomically (do t <- newEmptyTMVar; 
return t)
   threadDelay 100001
   --t <- forkIO $ oneThread stopFlag   -- this line would 
work fine...
   -- but the following one doesn't work.
   runInUnboundThread $ oneThread stopFlag
   threadDelay 100002
   atomically ( putTMVar stopFlag True )
   threadDelay 500003
   atomically ( putTMVar stopFlag False )
   return ()

oneThread stopFlag = do
   go <- atomically ( takeTMVar stopFlag )
   if  go  then  do putStrLn "-" 
                    oneThread stopFlag
	   else  return ()

   
Trac metadata
Trac field Value
Version 6.4
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution ResolvedFixed
Component libraries (other)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
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Reference: ghc/ghc#352