Hi Eugene <br>Thank you for reply. <br><br><div class="gmail_quote">On Wed, Sep 5, 2012 at 12:32 AM, Eugene Perederey <span dir="ltr"><<a href="mailto:eugene.perederey@gmail.com" target="_blank">eugene.perederey@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Why do you think main should block more than once?<br>
I see only two possible scenarios: the fun thread puts to mvar first<br>
thus blocking main,<br></blockquote><div><br>So at least in this case I should get thread blocked indefinitely in an MVar operation <br> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
or 10 is put into mvar in main, blocking the other thread indefinitely.<br></blockquote><div> <br>or main will execute and fun thread will die. There are 50 - 50 chance for this ( assuming both are equally likely ). I did some modification in my code and Now I am consistently getting "Concurrent: thread blocked indefinitely in an MVar operation"<br>
<br>import Data.List<br>import Control.Concurrent<br><br>fun m = do<br> putMVar m 10<br> return ()<br> <br><br>main = do <br> m <- newEmptyMVar <br> forkIO $ fun m<br> putStrLn "I am inside main"<br>
putMVar m 10<br> return ()<br><br>[mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp Concurrent.hs <br>[1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )<br>Linking Concurrent ...<br>
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>I am inside main<br>Concurrent: thread blocked indefinitely in an MVar operation<br>[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>I am inside main<br>Concurrent: thread blocked indefinitely in an MVar operation<br>
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>I am inside main<br>Concurrent: thread blocked indefinitely in an MVar operation<br>[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>I am inside main<br>Concurrent: thread blocked indefinitely in an MVar operation<br>
[mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>I am inside main<br>Concurrent: thread blocked indefinitely in an MVar operation<br> <br>My question is why the outcome in first case is deterministic. Every time the code executing ( at least half the time main thread should be blocked ) . <br>
<br>Regards <br>Mukesh Tiwari <br><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="h5"><br>
<br>
On 4 September 2012 11:54, mukesh tiwari <<a href="mailto:mukeshtiwari.iiitm@gmail.com">mukeshtiwari.iiitm@gmail.com</a>> wrote:<br>
> Hello All<br>
> I was going trough Real World Haskell and it says "If we try to put a value<br>
> into an MVar that is already full, our thread is put to sleep until another<br>
> thread takes the value out". I wrote a simple code to block main<br>
><br>
> import Data.List<br>
> import Control.Concurrent<br>
><br>
> fun m = do<br>
> putMVar m 10<br>
> return ()<br>
><br>
><br>
> main = do<br>
> m <- newEmptyMVar<br>
> forkIO $ fun m<br>
> putMVar m 10<br>
> return ()<br>
><br>
> What I am expecting that main should be blocked at least couple of times<br>
> but its behaving more deterministically.<br>
> [mukesh.tiwari@ Programming]$ ghc-7.4.1 -threaded -fforce-recomp<br>
> Concurrent.hs<br>
> [1 of 1] Compiling Main ( Concurrent.hs, Concurrent.o )<br>
> Linking Concurrent ...<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$ ./Concurrent +RTS -N2<br>
> [mukesh.tiwari@ Programming]$<br>
><br>
> I am expecting to get thread blocked indefinitely on MVar at least half the<br>
> time. Could some one please tell me why this deterministic behavior ?<br>
> Regards<br>
> Mukesh Tiwari<br>
><br>
><br>
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><br>
<span class="HOEnZb"><font color="#888888"><br>
<br>
<br>
--<br>
Best,<br>
Eugene Perederey<br>
</font></span></blockquote></div><br>