[commit: base] master: Adding a comment about the workaround of the parallel IO manager on Mac. (51a8b9b)

[Johan Tibell]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/51a8b9bb878247675b6e003fa081f1a22b2ae420

>---------------------------------------------------------------

commit 51a8b9bb878247675b6e003fa081f1a22b2ae420
Author: Kazu Yamamoto <kazu at iij.ad.jp>
Date:   Fri Feb 8 16:24:26 2013 +0900

    Adding a comment about the workaround of the parallel IO manager on Mac.

>---------------------------------------------------------------

 GHC/Event/Manager.hs |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/GHC/Event/Manager.hs b/GHC/Event/Manager.hs
index b764b6f..1dd9cc1 100644
--- a/GHC/Event/Manager.hs
+++ b/GHC/Event/Manager.hs
@@ -316,6 +316,15 @@ registerFd mgr cb fd evs = do
   return r
 {-# INLINE registerFd #-}
 
+{-
+    Building GHC with parallel IO manager on Mac freezes when
+    compiling the dph libraries in the phase 2. As workaround, we
+    don't use oneshot and we wake up an IO manager on Mac every time
+    when we register an event.
+
+    For more information, please read:
+        http://hackage.haskell.org/trac/ghc/ticket/7651
+-}
 -- | Wake up the event manager.
 wakeManager :: EventManager -> IO ()
 #if defined(darwin_HOST_OS)