GHC 7 can't do IO when demonized

If a daemon is complied with GHC 7.1 with the -threaded option, the daemon cannot do IO. The following code is a simple echo server which demonstrates this bug:

import Control.Concurrent
import Network
import System.IO
import System.Posix.Daemonize

main :: IO ()
main = daemonize $ do
    s <- listenOn (Service "7000")
    loop s
    return ()
    
loop :: Socket -> IO ThreadId
loop s = do
    (hdr,_,_) <- accept s
    forkIO $ echo hdr
    loop s
    
echo :: Handle -> IO ()
echo hdr = do
    str <- hGetLine hdr
    hPutStrLn hdr str
    hClose hdr
    return ()

If "deamonize $" is removed, this program stays in your terminal and can do IO.

Trac metadata

Trac field	Value
Version	7.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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