--- linux/kernel/pid.c.orig	
+++ linux/kernel/pid.c	
@@ -103,7 +103,7 @@ int alloc_pidmap(void)
 	pidmap_t *map;
 
 	pid = last_pid + 1;
-	if (pid >= pid_max)
+	if (unlikely(pid >= pid_max))
 		pid = RESERVED_PIDS;
 
 	offset = pid & BITS_PER_PAGE_MASK;
@@ -116,6 +116,10 @@ int alloc_pidmap(void)
 		 * slowpath and that fixes things up.
 		 */
 return_pid:
+		if (unlikely(pid >= pid_max)) {
+			clear_bit(offset, map->page);
+			goto failure;
+		}
 		atomic_dec(&map->nr_free);
 		last_pid = pid;
 		return pid;