When lazy IO blocks, it blocks the whole runtime

module Main where

import Control.Concurrent
import System.IO
import qualified Data.ByteString.Lazy.Char8 as B

heartbeat :: IO ()
heartbeat = do threadDelay 1000000
               putStrLn "."
               heartbeat

main :: IO ()
main = do forkIO heartbeat
          c <- B.getContents
          h <- openFile "/dev/null" WriteMode
          B.hPut h c

This should produce a heartbeat while it's waiting on stdin, but it doesn't, even with SMP:

dfranke@feanor:~% ghc --make brokenio.hs -threaded +RTS -N8
[1 of 1] Compiling Main             ( brokenio.hs, brokenio.o )
Linking brokenio ...
dfranke@feanor:~% sleep 5 | ./brokenio                     
dfranke@feanor:~%

Trac metadata

Trac field	Value
Version	6.8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	df@dfranke.us
Operating system
Architecture	Multiple