[commit: ghc] ghc-8.4: Always use the safe open() call (56fbfb3)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : ghc-8.4
Link       : http://ghc.haskell.org/trac/ghc/changeset/56fbfb3023b66d785cbfe1b33c6d8052d9205514/ghc

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

commit 56fbfb3023b66d785cbfe1b33c6d8052d9205514
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Mon Dec 11 12:56:09 2017 -0500

    Always use the safe open() call
    
    open() can sometimes take a long time, for example on NFS or FUSE
    filesystems.  We recently had a case where open() was taking multiple
    seconds to return for a (presumably overloaded) FUSE filesystem, which
    blocked GC and caused severe issues.
    
    Test Plan: validate
    
    Reviewers: niteria, bgamari, nh2, hvr, erikd
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie, carter
    
    GHC Trac Issues: #13296
    
    Differential Revision: https://phabricator.haskell.org/D4239
    
    (cherry picked from commit cafe98345cb5d4b11f2059d60d2f20e976ef4f2a)


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

56fbfb3023b66d785cbfe1b33c6d8052d9205514
 libraries/base/GHC/IO/FD.hs | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/libraries/base/GHC/IO/FD.hs b/libraries/base/GHC/IO/FD.hs
index a7a34c1..4a4f063 100644
--- a/libraries/base/GHC/IO/FD.hs
+++ b/libraries/base/GHC/IO/FD.hs
@@ -179,14 +179,10 @@ openFile filepath iomode non_blocking =
              | otherwise    = oflags2
     in do
 
-    -- the old implementation had a complicated series of three opens,
-    -- which is perhaps because we have to be careful not to open
-    -- directories.  However, the man pages I've read say that open()
-    -- always returns EISDIR if the file is a directory and was opened
-    -- for writing, so I think we're ok with a single open() here...
-    fd <- throwErrnoIfMinus1Retry "openFile"
-                (if non_blocking then c_open      f oflags 0o666
-                                 else c_safe_open f oflags 0o666)
+    -- NB. always use a safe open(), because we don't know whether open()
+    -- will be fast or not.  It can be slow on NFS and FUSE filesystems,
+    -- for example.
+    fd <- throwErrnoIfMinus1Retry "openFile" $ c_safe_open f oflags 0o666
 
     (fD,fd_type) <- mkFD fd iomode Nothing{-no stat-}
                             False{-not a socket-}