[commit: base] master: Release the FD lock before calling close() (#7646) (fbd4b4c)

[Simon Marlow]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/fbd4b4c2587636811d464040e349d81fac9e1121

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

commit fbd4b4c2587636811d464040e349d81fac9e1121
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Mon Feb 4 12:08:00 2013 +0000

    Release the FD lock before calling close() (#7646)

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

 GHC/IO/FD.hs |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/GHC/IO/FD.hs b/GHC/IO/FD.hs
index 0f37a81..fdeeb74 100644
--- a/GHC/IO/FD.hs
+++ b/GHC/IO/FD.hs
@@ -315,7 +315,6 @@ stderr = stdFD 2
 
 close :: FD -> IO ()
 close fd =
-  (flip finally) (release fd) $
   do let closer realFd =
            throwErrnoIfMinus1Retry_ "GHC.IO.FD.close" $
 #ifdef mingw32_HOST_OS
@@ -324,6 +323,12 @@ close fd =
            else
 #endif
              c_close (fromIntegral realFd)
+
+     -- release the lock *first*, because otherwise if we're preempted
+     -- after closing but before releasing, the FD may have been reused.
+     -- (#7646)
+     release fd
+
      closeFdWith closer (fromIntegral (fdFD fd))
 
 release :: FD -> IO ()