id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5784	Forked thread running infinite loop blocks other threads from running	joeyadams		"When I compile the following under GHC 7.2.2 with -O1 or -O2, it spins in the forked thread's infinite loop.  The forked thread does not yield control to the main thread:

{{{
import Control.Concurrent
import Control.Monad

main :: IO ()
main = do
    tid <- forkIO $ forever $ return ()
    putStrLn $ ""Forked "" ++ show tid
}}}

This happens up even if I compile with -threaded -rtsopts, use +RTS -N2, and use forkOS instead of forkIO.

The problem goes away if I disable optimization.  It also goes away if I stick a yield :: IO () call in the loop."	bug	closed	normal		Runtime System	7.2.2	duplicate		leon.p.smith@… mcallister.keegan@…	Linux	x86_64 (amd64)	Incorrect result at runtime	Unknown