avoid useless fcntl in rb_io_set_nonblock.

git-svn-id: http://svn.ruby-lang.org/repos/ruby/trunk@10180 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 3 deletions

diff --git a/io.c b/io.c
index 22257b65a..83c51f443 100644
--- a/io.c
+++ b/io.c
@@ -1247,9 +1247,11 @@ void rb_io_set_nonblock(OpenFile *fptr)
 #else
     flags = 0;
 #endif
-    flags |= O_NONBLOCK;
-    if (fcntl(fptr->fd, F_SETFL, flags) == -1) {
-        rb_sys_fail(fptr->path);
+    if ((flags & O_NONBLOCK) == 0) {
+        flags |= O_NONBLOCK;
+        if (fcntl(fptr->fd, F_SETFL, flags) == -1) {
+            rb_sys_fail(fptr->path);
+        }
     }
 }