GQ-EDF: don't blindly overwrite entry->linked (bugfix)

Check if an already-linked task must be re-inserted into
the ready queue.

1 files changed, 10 insertions, 3 deletions

diff --git a/litmus/sched_gq_edf.c b/litmus/sched_gq_edf.c
index f27bf51341..e630fe926d 100644
--- a/litmus/sched_gq_edf.c
+++ b/litmus/sched_gq_edf.c
@@ -411,7 +411,7 @@ static void gq_finish_switch(struct task_struct *prev)
 static void gq_task_new(struct task_struct * t, int on_rq, int running)
 {
         unsigned long   flags;
-        cpu_state_t*    entry;
+        cpu_state_t*    entry = NULL;
         int             on_rm = 0;
 
         spin_lock_irqsave(&gq_lock, flags);
@@ -434,9 +434,16 @@ static void gq_task_new(struct task_struct * t, int on_rq, int running)
         if (running && !on_rm) {
                 /* just leave it where it is, CPU was real-time idle */
                 tsk_rt(t)->scheduled_on = task_cpu(t);
-                tsk_rt(t)->linked_on    = task_cpu(t);
-                entry->linked    = t;
+                tsk_rt(t)->linked_on = task_cpu(t);
                 entry->scheduled = t;
+                if (entry->linked != NULL) {
+                        /* Something raced and got assigned here.
+                         * Kick it back into the queue, since t is
+                         * already executing.
+                         */
+                        __add_ready(&gqedf, entry->linked);
+                }
+                entry->linked = t;
         }
 
         if (!running || on_rm) {