1 files changed, 22 insertions, 4 deletions

diff --git a/litmus/sched_gsn_edf.c b/litmus/sched_gsn_edf.c
index 69990805e16a..a223e69f2efb 100644
--- a/litmus/sched_gsn_edf.c
+++ b/litmus/sched_gsn_edf.c
@@ -393,6 +393,12 @@ static struct task_struct* gsnedf_schedule(struct task_struct * prev)
         int out_of_time, sleep, preempt, np, exists, blocks;
         struct task_struct* next = NULL;
 
+        /* Bail out early if we are the release master.
+         * The release master never schedules any real-time tasks.
+         */
+        if (gsnedf.release_master == entry->cpu)
+                return NULL;
+
         spin_lock(&gsnedf_lock);
         clear_will_schedule();
 
@@ -515,8 +521,15 @@ static void gsnedf_task_new(struct task_struct * t, int on_rq, int running)
         if (running) {
                 entry = &per_cpu(gsnedf_cpu_entries, task_cpu(t));
                 BUG_ON(entry->scheduled);
-                entry->scheduled = t;
-                tsk_rt(t)->scheduled_on = task_cpu(t);
+
+                if (entry->cpu != gsnedf.release_master) {
+                        entry->scheduled = t;
+                        tsk_rt(t)->scheduled_on = task_cpu(t);
+                } else {
+                        /* do not schedule on release master */
+                        preempt(entry); /* force resched */
+                        tsk_rt(t)->scheduled_on = NO_CPU;
+                }
         } else {
                 t->rt_param.scheduled_on = NO_CPU;
         }
@@ -758,6 +771,7 @@ static long gsnedf_activate_plugin(void)
         cpu_entry_t *entry;
 
         heap_init(&gsnedf_cpu_heap);
+        gsnedf.release_master = atomic_read(&release_master_cpu);
 
         for_each_online_cpu(cpu) {
                 entry = &per_cpu(gsnedf_cpu_entries, cpu);
@@ -765,8 +779,12 @@ static long gsnedf_activate_plugin(void)
                 atomic_set(&entry->will_schedule, 0);
                 entry->linked    = NULL;
                 entry->scheduled = NULL;
-                TRACE("GSN-EDF: Initializing CPU #%d.\n", cpu);
-                update_cpu_position(entry);
+                if (cpu != gsnedf.release_master) {
+                        TRACE("GSN-EDF: Initializing CPU #%d.\n", cpu);
+                        update_cpu_position(entry);
+                } else {
+                        TRACE("GSN-EDF: CPU %d is release master.\n", cpu);
+                }
         }
         return 0;
 }