edf_common: allow comparison of two NULL pointers

If the first argument to edf_higher_prio is NULL, then just
return 0, since it can't possibly have a higher piority than the
second argument.

1 files changed, 4 insertions, 3 deletions

diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index 253641de4f..84ece3e95e 100644
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -18,8 +18,7 @@
 /* edf_higher_prio -  returns true if first has a higher EDF priority
  *                    than second. Deadline ties are broken by PID.
  *
- * first first must not be NULL and a real-time task.
- * second may be NULL or a non-rt task.
+ * both first and second may be NULL
  */
 int edf_higher_prio(struct task_struct* first,
                     struct task_struct* second)
@@ -36,6 +35,8 @@ int edf_higher_prio(struct task_struct* first,
                 second_task = second->rt_param.inh_task;
 
         return
+                /* it has to exist in order to have higher priority */
+                first_task && (
                 /* does the second task exist and is it a real-time task?  If
                  * not, the first task (which is a RT task) has higher
                  * priority.
@@ -57,7 +58,7 @@ int edf_higher_prio(struct task_struct* first,
                  * priority wins.
                  */
                 (first_task->pid == second_task->pid &&
-                 !second->rt_param.inh_task)));
+                 !second->rt_param.inh_task))));
 }
 
 int edf_ready_order(struct heap_node* a, struct heap_node* b)