RE: [Haskell-cafe] Re: Thread pool in GHC

5 Sep 2005

      Its probably too long to bring back this topic, but i have a small question.

If some threads may never terminate and have to be killed by killThread, are 
they going back to the pool, or we need some twist to force them.

Thanks a lot
TuanAnh
...
From: genneth 
To: haskell-cafe@haskell.org
Subject: [Haskell-cafe] Re: Thread pool in GHC
Date: Thu, 4 Aug 2005 16:47:56 +0000 (UTC)
Dinh Tien Tuan Anh  writes:
...
Can thread pool be implemented in GHC ?
I have a program that is currently using about 12-15 threads (launch and
kill for infinite times) and when running, especially after Ctrl-C, my
computer got freezed up. And if i ran it several times, the "Stack
overflows" occurs.
I made the following a while back. Maybe it's useful...
limitedThreadsWithChannelMapM :: Integer -> (a -> IO b) -> [a] -> IO [MVar 
b]
limitedThreadsWithChannelMapM lim ioaction x = do
    threadpoolcounter <- atomically ( newTVar 0 )
    mapM (throttledFork threadpoolcounter . ioaction) x
    where
        throttledFork poolcount io = do
            atomically ( do
                prev <- readTVar poolcount
                if prev >= lim then
                    retry
                    else writeTVar poolcount (prev+1) )
            mvar <- newEmptyMVar
            forkIO(
                finally
                    (io >>= putMVar mvar)
                    (atomically ( readTVar poolcount >>= writeTVar 
poolcount .
(subtract 1) ) ) )
            return mvar
...
Cheers
TuanAnh
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