In case anyone wants to contribute to it, I have submitted a bug report [1].
Best, Facundo [1] https://ghc.haskell.org/trac/ghc/ticket/8521 On Mon, Oct 21, 2013 at 9:03 AM, Facundo Domínguez <facundo.doming...@parsci.com> wrote: >> Oh I see; the problem is the GHC RTS is attempting to shut down, >> and in order to do this it needs to grab all of the capabilities. > > Thanks, again. However, the program doesn't seem to be blocking when > the main thread finishes, but rather in the "takeMVar mv1" line. I'm > copying the modified version with a print call that never manages to > print in the console for me. > > btw, I'm using ghc 7.6.3. > > Best, > Facundo > > ----- > > 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 > > On Sun, Oct 20, 2013 at 2:37 AM, Edward Z. Yang <ezy...@mit.edu> wrote: >> Oh I see; the problem is the GHC RTS is attempting to shut down, >> and in order to do this it needs to grab all of the capabilities. However, >> one of them is in an uninterruptible loop, so the program hangs (e.g. >> if you change the program as follows: >> >> main :: IO () >> main = do >> forkIO $ do >> loop (y == ["yield"]) >> threadDelay 1000 >> ) >> >> With a sufficiently recent version of GHC, if you compile with >> -fno-omit-yields, >> that should fix the problem. >> >> Edward >> >> Excerpts from Facundo Domínguez's message of Sat Oct 19 16:05:15 -0700 2013: >>> Thanks. I just tried that. Unfortunately, it doesn't seem to help. >>> >>> Facundo >>> >>> On Sat, Oct 19, 2013 at 8:47 PM, Edward Z. Yang <ezy...@mit.edu> wrote: >>> > Hello Facundo, >>> > >>> > The reason is that you have compiled the program to be multithreaded, but >>> > it >>> > is not running with multiple cores. Compile also with -rtsopts and then >>> > pass +RTS -N2 to the program. >>> > >>> > Excerpts from Facundo Domínguez's message of Sat Oct 19 15:19:22 -0700 >>> > 2013: >>> >> Hello, >>> >> Below is a program that seems to block indefinitely with ghc in a >>> >> multicore machine. This program has a loop that does not produce >>> >> allocations, and I understand that this may grab one of the cores. The >>> >> question is, why can't the other cores take the blocked thread? >>> >> >>> >> The program was compiled with: >>> >> >>> >> $ ghc --make -O -threaded test.hs >>> >> >>> >> and it is run with: >>> >> >>> >> $ ./test >>> >> >>> >> Program text follows. >>> >> >>> >> Thanks, >>> >> Facundo >>> >> >>> >> -------- >>> >> >>> >> 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 >>> >> >>> >> loop :: Bool -> IO () >>> >> loop cooperative = go >>> >> where >>> >> go = when cooperative yield >> go >> _______________________________________________ >> Glasgow-haskell-users mailing list >> Glasgow-haskell-users@haskell.org >> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
