ktest: Make sure wait_for_input does honor the timeout

The function wait_for_input takes in a timeout, and even has a default
timeout. But if for some reason the STDIN descriptor keeps sending in data,
the function will never time out. The timout is to wait for the data from
the passed in file descriptor, not for STDIN. Adding a test in the case
where there's no data from the passed in file descriptor that checks to see
if the timeout passed, will ensure that it will timeout properly even if
there's input in STDIN.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/testing/ktest/ktest.pl

@@ -1880,6 +1880,7 @@ sub get_grub_index {
 sub wait_for_input
 {
     my ($fp, $time) = @_;
+    my $start_time;
     my $rin;
     my $rout;
     my $nr;
@@ -1895,12 +1896,12 @@ sub wait_for_input
     vec($rin, fileno($fp), 1) = 1;
     vec($rin, fileno(\*STDIN), 1) = 1;
 
+    $start_time = time;
+
     while (1) {
 	$nr = select($rout=$rin, undef, undef, $time);
 
-	if ($nr <= 0) {
-	    return undef;
-	}
+	last if ($nr <= 0);
 
 	# copy data from stdin to the console
 	if (vec($rout, fileno(\*STDIN), 1) == 1) {
@@ -1908,7 +1909,11 @@ sub wait_for_input
 	    syswrite($fp, $buf, $nr) if ($nr > 0);
 	}
 
-	next if (vec($rout, fileno($fp), 1) != 1);
+	# The timeout is based on time waiting for the fp data
+	if (vec($rout, fileno($fp), 1) != 1) {
+	    last if (defined($time) && (time - $start_time > $time));
+	    next;
+	}
 
 	$line = "";
 
@@ -1918,12 +1923,11 @@ sub wait_for_input
 	    last if ($ch eq "\n");
 	}
 
-	if (!length($line)) {
-	    return undef;
-	}
+	last if (!length($line));
 
 	return $line;
     }
+    return undef;
 }
 
 sub reboot_to {