Fix hang from bug in edf_common.c

1 files changed, 31 insertions, 5 deletions

diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index a1cdc10ea6f1..39ce1816ee04 100644
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -185,11 +185,37 @@ int edf_higher_prio(struct task_struct* first, struct task_struct* second)
                                         return 1;
                                 }
 #endif
-                                /* If the PIDs are the same then the task with the
-                                 * inherited priority wins.
-                                 */
-                                if (!second_task->rt_param.inh_task) {
-                                        return 1;
+                                /* Something could be wrong if you get this far. */
+                                if (unlikely(first->rt_param.inh_task ==
+                                                                                second->rt_param.inh_task)) {
+                                        /* Both tasks have the same inherited priority.
+                                         * Likely in a bug-condition.
+                                     */
+                                        if (likely(first->pid < second->pid)) {
+                                                return 1;
+                                        }
+                                        else if (first->pid == second->pid) {
+                                                WARN_ON(1);
+                                        }
+                                }
+                                else {
+                                        /* At least one task must inherit */
+                                        BUG_ON(!first->rt_param.inh_task &&
+                                                   !second->rt_param.inh_task);
+
+                                        /* The task with the inherited priority wins. */
+                                        if (!second->rt_param.inh_task) {
+                                                TRACE_CUR("unusual comparison: "
+                                                        "first = %s/%d  first_task = %s/%d  "
+                                                        "second = %s/%d  second_task = %s/%d\n",
+                                                        first->comm, first->pid,
+                                                        (first->rt_param.inh_task) ? first->rt_param.inh_task->comm : "(nil)",
+                                                        (first->rt_param.inh_task) ? first->rt_param.inh_task->pid : 0,
+                                                        second->comm, second->pid,
+                                                        (second->rt_param.inh_task) ? second->rt_param.inh_task->comm : "(nil)",
+                                                        (second->rt_param.inh_task) ? second->rt_param.inh_task->pid : 0);
+                                                return 1;
+                                        }
                                 }
                         }
                 }