[commit: base] master: Fix bug that caused ghci to create a large number of kqueues and pipes on OS X. (a372e40)

[Johan Tibell]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/a372e4050f4d0bca33657e677a735aaa6ef88e58

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

commit a372e4050f4d0bca33657e677a735aaa6ef88e58
Author: Andreas Voellmy <andreas.voellmy at gmail.com>
Date:   Sun Feb 10 15:06:37 2013 -0800

    Fix bug that caused ghci to create a large number of kqueues and pipes on OS X.
    
    This is caused because ensureIOManagerIsRunning is repeatedly called and this was initializing new IO managers on each call. Fixed so that a new manager is not created if one already exists.

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

 GHC/Event/Thread.hs |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/GHC/Event/Thread.hs b/GHC/Event/Thread.hs
index 9a43b4f..cbef3c3 100644
--- a/GHC/Event/Thread.hs
+++ b/GHC/Event/Thread.hs
@@ -276,11 +276,7 @@ startIOManagerThread eventManagerArray i = do
           -- See #4449
           M.cleanup em
           create
-        _other         -> do
-          -- Another thread is currently servicing the manager loop.
-          -- Tell it to exit and start a new thread to work on the loop.
-          M.release em
-          create
+        _other         -> return ()
 
 startTimerManagerThread :: IO ()
 startTimerManagerThread = modifyMVar_ timerManagerThreadVar $ \old -> do