[GHC] #4504: "awaitSignal Nothing" does not block thread with -threaded

[GHC]

#4504: "awaitSignal Nothing" does not block thread with -threaded
---------------------------------+------------------------------------------
    Reporter:  adept             |       Owner:                             
        Type:  bug               |      Status:  new                        
    Priority:  normal            |   Component:  Runtime System             
     Version:  7.0.1             |    Keywords:                             
    Testcase:                    |   Blockedby:                             
          Os:  Unknown/Multiple  |    Blocking:                             
Architecture:  Unknown/Multiple  |     Failure:  Incorrect result at runtime
---------------------------------+------------------------------------------
 Consider the following code:

 {{{
 module Main where

 import System.Posix.Signals
 import Control.Concurrent

 main :: IO ()
 main = do
   awaitSignal Nothing >> yield
 }}}

 According to the System.Posix.Signals haddock, "awaitSignal Nothing"
 should call pause(2), causing main thread to block until some signal has
 arrived. This is indeed what happens when this code is compiled by GHC
 7.0.1 like so: "ghc --make awaitSignal.hs".

 However, when compiled with -threaded, this code exits immediately when
 run. I think this is a bug in -threaded runtime.

 I've tested with GHC 6.12.1, and this behavior is present there as well.
 Maybe I'm missing something non-obvious here?

 My environment: x86, Debian sid, GHC 6.12.1 from Debian packages, GHC
 7.0.1 from binary packages from GHC site.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4504>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler