From 0eb4bba10f3d6c9143d73fb8cadb11eba1a5dbd9 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Thu, 11 May 2000 13:15:38 +0000
Subject: [PATCH] [project @ 2000-05-11 13:15:38 by simonmar] Don't open with
O_NONBLOCK, instead open in blocking mode and set O_NONBLOCK subsequently
with fcntl(). This appears to fix the problems with FIFOs.
Pick one of the following:
- the semantics as implemented by Linux & Solaris is broken
- the POSIX semantics is broken
- our expectation that things should behave sensibly is unreasonable
---
ghc/lib/std/cbits/openFile.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/ghc/lib/std/cbits/openFile.c b/ghc/lib/std/cbits/openFile.c
index 8930fe568d79..57b0c2ff848b 100644
--- a/ghc/lib/std/cbits/openFile.c
+++ b/ghc/lib/std/cbits/openFile.c
@@ -1,7 +1,7 @@
/*
* (c) The GRASP/AQUA Project, Glasgow University, 1994-1998
*
- * $Id: openFile.c,v 1.16 2000/04/12 17:33:16 simonmar Exp $
+ * $Id: openFile.c,v 1.17 2000/05/11 13:15:38 simonmar Exp $
*
* openFile Runtime Support
*/
@@ -94,22 +94,22 @@ openFile(StgByteArray file, StgInt how, StgInt binary)
switch (how) {
case OPENFILE_APPEND:
- oflags = O_NONBLOCK | O_WRONLY | O_NOCTTY | O_APPEND;
+ oflags = O_WRONLY | O_NOCTTY | O_APPEND;
for_writing = 1;
flags |= FILEOBJ_WRITE;
break;
case OPENFILE_WRITE:
- oflags = O_NONBLOCK | O_WRONLY | O_NOCTTY;
+ oflags = O_WRONLY | O_NOCTTY;
flags |= FILEOBJ_WRITE;
for_writing = 1;
break;
case OPENFILE_READ_ONLY:
- oflags = O_NONBLOCK | O_RDONLY | O_NOCTTY;
+ oflags = O_RDONLY | O_NOCTTY;
flags |= FILEOBJ_READ;
for_writing = 0;
break;
case OPENFILE_READ_WRITE:
- oflags = O_NONBLOCK | O_RDWR | O_NOCTTY;
+ oflags = O_RDWR | O_NOCTTY;
flags |= FILEOBJ_READ | FILEOBJ_WRITE;
for_writing = 1;
break;
@@ -191,8 +191,17 @@ openFile(StgByteArray file, StgInt how, StgInt binary)
}
}
- /* Make sure that we aren't looking at a directory */
+ /* Set non-blocking mode *after* the open. The reason is that
+ * when reading from a FIFO, if we open in non-blocking mode
+ * then any reads from the FIFO will return EOF straight away
+ * without waiting for a writing process. If we set O_NONBLOCK
+ * after doing the open, then we apparently get to wait for a
+ * writer. This broken behaviour has been observed on both Linux
+ * & Solaris. --SDM
+ */
+ fcntl(fd, F_SETFL, oflags | O_NONBLOCK);
+ /* Make sure that we aren't looking at a directory */
while (fstat(fd, &sb) < 0) {
/* highly unlikely */
if (errno != EINTR) {
--
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