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Re: [Xen-devel] [PATCH] libxl: use libxl_fd_set_{cloexec, nonblock} helpers

On 07/28/14 10:51, David Vrabel wrote:
On 28/07/14 07:32, Jan Beulich wrote:
On 25.07.14 at 19:07, <Ian.Jackson@xxxxxxxxxxxxx> wrote:
Jan Beulich writes ("[PATCH] libxl: use libxl_fd_set_{cloexec,nonblock}
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -358,19 +358,14 @@ static int qmp_open(libxl__qmp_handler *
                      int timeout)
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -1047,11 +1047,17 @@ int libxl__random_bytes(libxl__gc *gc, u
-    fd = open(dev, O_RDONLY | O_CLOEXEC);
+    fd = open(dev, O_RDONLY);
Firstly, I don't understand why we care about cloexec on this fd, but
it's harmless to do so.
And of course I'd be perfectly fine with a one liner just dropping it
(all I really care about is that the file builds correctly in all cases).
The question of why cloexec is needed/wanted here I'll pass on to
author and committer, but I'd guess this is just to avoid
proliferation of file handles into clones.
Surely it should be standard practice for a library to always set
CLOEXEC on any files it opens, to minimize the side effects the library
call has?

And if CLOEXEC is required then setting it at open time is the only safe


Since this is an open, read, close; CLOEXEC is not needed at all. And it breaks
the build on RHEL5.  So I did a quick one liner.

From 46e776a2b770857d869ef54c418924af043274d0 Mon Sep 17 00:00:00 2001
From: Don Slutz <dslutz@xxxxxxxxxxx>
Date: Thu, 31 Jul 2014 01:26:58 +0000
Subject: [PATCH] Make RHEL5 build again

Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
 tools/libxl/libxl_utils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libxl/libxl_utils.c b/tools/libxl/libxl_utils.c
index 1fdf5ea..2649778 100644
--- a/tools/libxl/libxl_utils.c
+++ b/tools/libxl/libxl_utils.c
@@ -1047,7 +1047,7 @@ int libxl__random_bytes(libxl__gc *gc, uint8_t *buf, size_t len)
     int fd;
     int ret;

-    fd = open(dev, O_RDONLY | O_CLOEXEC);
+    fd = open(dev, O_RDONLY);
     if (fd < 0) {
         LOGE(ERROR, "failed to open \"%s\"", dev);
         return ERROR_FAIL;

   -Don Slutz

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