Fixed bug where finish switch could strand level-C tasks in neverland

2 files changed, 15 insertions, 6 deletions

diff --git a/litmus/rt_domain.c b/litmus/rt_domain.c
index 93f2a35fb29d..f242f33e990e 100644
--- a/litmus/rt_domain.c
+++ b/litmus/rt_domain.c
@@ -20,7 +20,7 @@
 #include <litmus/bheap.h>
 
 /* Uncomment when debugging timer races... */
-#if 1
+#if 0
 #define VTRACE_TASK TRACE_TASK
 #define VTRACE TRACE
 #else
@@ -404,7 +404,9 @@ void __add_release(rt_domain_t* rt, struct task_struct *task)
 static void pd_requeue(domain_t *dom, struct task_struct *task)
 {
         rt_domain_t *domain = (rt_domain_t*)dom->data;
+
         BUG_ON(!task || !is_realtime(task));
+        TRACE_TASK(task, "Requeueing");
         BUG_ON(is_queued(task));
         BUG_ON(get_task_domain(task) != dom);
 
diff --git a/litmus/sched_mc.c b/litmus/sched_mc.c
index 277762709d3d..61eb961eda23 100644
--- a/litmus/sched_mc.c
+++ b/litmus/sched_mc.c
@@ -63,8 +63,10 @@ static int interrupt_cpu;
 #define is_global_task(t) (is_global(get_task_domain(t)))
 #define can_use(ce) \
         ((ce)->state == CS_ACTIVE || (ce->state == CS_ACTIVATE))
-#define can_requeue(t)                                  \
-        (!is_global_task(t) || (t)->rt_param.scheduled_on == NO_CPU)
+#define can_requeue(t)                                                  \
+        ((t)->rt_param.linked_on == NO_CPU && /* Not linked anywhere */ \
+         !is_queued(t) &&                     /* Not gonna be linked */ \
+         (!is_global_task(t) || (t)->rt_param.scheduled_on == NO_CPU))
 #define entry_level(e) \
         (((e)->linked) ? tsk_mc_crit((e)->linked) : NUM_CRIT_LEVELS - 1)
 #define crit_cpu(ce) \
@@ -288,11 +290,11 @@ static void job_arrival(struct task_struct *task)
         TRACE_MC_TASK(task, "Job arriving\n");
         BUG_ON(!task);
 
+        raw_spin_lock(dom->lock);
         if (can_requeue(task)) {
-                raw_spin_lock(dom->lock);
+                BUG_ON(task->rt_param.linked_on != NO_CPU);
                 dom->requeue(dom, task);
                 check_for_preempt(dom);
-                raw_spin_unlock(dom->lock);
         } else {
                 /* If a global task is scheduled on one cpu, it CANNOT
                  * be requeued into a global domain. Another cpu might
@@ -302,6 +304,7 @@ static void job_arrival(struct task_struct *task)
                  */
                 TRACE_MC_TASK(task, "Delayed arrival of scheduled task\n");
         }
+        raw_spin_unlock(dom->lock);
 }
 
 /**
@@ -547,11 +550,15 @@ static void remove_from_all(struct task_struct* task)
                                 update = 1;
                                 link_task_to_cpu(entry, NULL);
                         }
+                } else {
+                        TRACE_MC_TASK(task, "Unlinked before we got lock!");
                 }
                 if (update)
                         update_crit_levels(entry);
                 else
                         raw_spin_unlock(&entry->lock);
+        } else {
+                TRACE_MC_TASK(task, "Not linked to anything\n");
         }
 
         /* Ensure the task isn't returned by its domain */
@@ -874,7 +881,7 @@ static struct task_struct* mc_schedule(struct task_struct* prev)
         local_irq_save(flags);
         raw_spin_lock(&entry->lock);
 
-        if (entry->scheduled) {
+        if (entry->scheduled && entry->scheduled != prev) {
                 TRACE_TASK(entry->scheduled, " and prev is %d\n", prev->pid);
         }