ruby.c: reduce fstat

* file.c (ruby_is_fd_loadable): now return -1 if loadable but
  may block.
* ruby.c (open_load_file): wait to read by the result of
  ruby_is_fd_loadable, without fstat.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54099 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Mon Mar 14 16:02:59 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* file.c (ruby_is_fd_loadable): now return -1 if loadable but
+	  may block.
+
+	* ruby.c (open_load_file): wait to read by the result of
+	  ruby_is_fd_loadable, without fstat.
+
 Mon Mar 14 13:38:38 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* numeric.c (fix2str): improve r54092 like rb_int2big().

file.c

@@ -5644,11 +5644,12 @@ ruby_is_fd_loadable(int fd)
 
     if (fstat(fd, &st) < 0)
 	return 0;
+
     if (S_ISREG(st.st_mode))
 	return 1;
 
     if (S_ISFIFO(st.st_mode))
-	return 1;
+	return -1;
 
     if (S_ISDIR(st.st_mode))
 	errno = EISDIR;

ruby.c

@@ -1871,15 +1871,14 @@ open_load_file(VALUE fname_v, int *xflag)
 	}
 #endif
 
-#ifdef S_ISFIFO
-	{
-	    struct stat st;
-	    if (fstat(fd, &st) != 0) {
+	e = ruby_is_fd_loadable(fd);
+	if (e <= 0) {
+	    if (!e) {
 		e = errno;
 		(void)close(fd);
 		rb_load_fail(fname_v, strerror(e));
 	    }
-	    if (S_ISFIFO(st.st_mode)) {
+	    else {
 		/*
 		  We need to wait if FIFO is empty. It's FIFO's semantics.
 		  rb_thread_wait_fd() release GVL. So, it's safe.
@@ -1887,12 +1886,6 @@ open_load_file(VALUE fname_v, int *xflag)
 		rb_thread_wait_fd(fd);
 	    }
 	}
-#endif
-	if (!ruby_is_fd_loadable(fd)) {
-	    e = errno;
-	    (void)close(fd);
-	    rb_load_fail(fname_v, strerror(e));
-	}
 
 	f = rb_io_fdopen(fd, mode, fname);
     }