Clean up remnants of the Event Manager after forkProcess. Closes #4449

[ghc-base.git] / System / Event / Manager.hs

diff --git a/System/Event/Manager.hs b/System/Event/Manager.hs
index 74b1a72..0c8293f 100644 (file)
--- a/System/Event/Manager.hs
+++ b/System/Event/Manager.hs
@@ -14,6 +14,7 @@ module System.Event.Manager
     , loop
     , step
     , shutdown
+    , cleanup
     , wakeManager
 
       -- * Registering interest in I/O events
@@ -41,8 +42,7 @@ module System.Event.Manager
 ------------------------------------------------------------------------
 -- Imports
 
-import Control.Concurrent.MVar (MVar, modifyMVar, modifyMVar_, newMVar,
-                                readMVar)
+import Control.Concurrent.MVar (MVar, modifyMVar, newMVar, readMVar)
 import Control.Exception (finally)
 import Control.Monad ((=<<), forM_, liftM, sequence_, when)
 import Data.IORef (IORef, atomicModifyIORef, mkWeakIORef, newIORef, readIORef,
@@ -97,6 +97,7 @@ type IOCallback = FdKey -> Event -> IO ()
 instance Show IOCallback where
     show _ = "IOCallback"
 
+-- | A timeout registration cookie.
 newtype TimeoutKey   = TK Unique
     deriving (Eq)
 
@@ -218,7 +219,8 @@ cleanup EventManager{..} = do
 ------------------------------------------------------------------------
 -- Event loop
 
--- | Start handling events.  This function loops until told to stop.
+-- | Start handling events.  This function loops until told to stop,
+-- using 'shutdown'.
 --
 -- /Note/: This loop can only be run once per 'EventManager', as it
 -- closes all of its control resources when it finishes.
@@ -347,7 +349,10 @@ closeFd mgr close fd = do
 ------------------------------------------------------------------------
 -- Registering interest in timeout events
 
--- | Register a timeout in the given number of microseconds.
+-- | Register a timeout in the given number of microseconds.  The
+-- returned 'TimeoutKey' can be used to later unregister or update the
+-- timeout.  The timeout is automatically unregistered after the given
+-- time has passed.
 registerTimeout :: EventManager -> Int -> TimeoutCallback -> IO TimeoutKey
 registerTimeout mgr us cb = do
   !key <- newUnique (emUniqueSource mgr)
@@ -366,12 +371,15 @@ registerTimeout mgr us cb = do
       wakeManager mgr
   return $ TK key
 
+-- | Unregister an active timeout.
 unregisterTimeout :: EventManager -> TimeoutKey -> IO ()
 unregisterTimeout mgr (TK key) = do
   atomicModifyIORef (emTimeouts mgr) $ \f ->
       let f' = (Q.delete key) . f in (f', ())
   wakeManager mgr
 
+-- | Update an active timeout to fire in the given number of
+-- microseconds.
 updateTimeout :: EventManager -> TimeoutKey -> Int -> IO ()
 updateTimeout mgr (TK key) us = do
   now <- getCurrentTime