Fixed priority inheritance issues with PI semaphores. Added regular

semaphores accessible through system calls, so that they can be used with
the LSO (for partitioned FMLP).

1 files changed, 22 insertions, 18 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 379b71bc47..b9bcda8fb7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1628,7 +1628,8 @@ void fastcall sched_fork(struct task_struct *p, int clone_flags)
         INIT_LIST_HEAD(&p->rt_list);
         p->rt_param.basic_params.class = RT_CLASS_BEST_EFFORT;
         p->rt_param.litmus_controlled  = 0;
-        p->rt_param.has_resource = 0;
+        p->rt_param.released_pi_sem = 0;
+        p->rt_param.inh_task = NULL;
         p->rt_param.waiting_to_exit_zone = 0;
         p->array = NULL;
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
@@ -3813,8 +3814,6 @@ static void __pi_wake_up_common(struct pi_semaphore *s, unsigned int mode,
                                 int nr_exclusive, int sync, void *key)
 {
         struct list_head *tmp, *next;
-        jiffie_t task_prio;
-        jiffie_t highest_prio = LOWEST_SEM_PRIO;
 
         /* First pass: wakeup tasks. */
         list_for_each_safe(tmp, next, &s->wait.task_list) {
@@ -3826,25 +3825,30 @@ static void __pi_wake_up_common(struct pi_semaphore *s, unsigned int mode,
                         break;
         }
 
-        /* Second pass: find highest-priority sleeping task. */
-        list_for_each_safe(tmp, next, &s->wait.task_list) {                 
-                wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
-                
-                /* Compare task priorities, find highest (earliest d/l). */
-                task_prio = ((struct task_struct *)curr->private)->rt_param.times.deadline;
-                if (time_before(task_prio, highest_prio)) {
-                        highest_prio = task_prio;
+        /* Second pass: find highest-priority sleeping task,
+         * _if current task is the current sem_hp_task_.
+         */
+        if (current == s->sem_hp_task) {
+                s->sem_hp_task = NULL;
+                list_for_each_safe(tmp, next, &s->wait.task_list) {                 
+                        wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
+                        
+                        /* Compare task priorities, find highest priority task. */
+                        if (!s->sem_hp_task ||
+                            time_before(((struct task_struct *)curr->private)->rt_param.times.deadline,
+                                        s->sem_hp_task->rt_param.times.deadline) ||
+                            (((struct task_struct *)curr->private)->rt_param.times.deadline ==
+                             s->sem_hp_task->rt_param.times.deadline &&
+                             ((struct task_struct *)curr->private)->pid < s->sem_hp_task->pid))
+                                s->sem_hp_task = (struct task_struct *)curr->private;
                 }
         }
 
-        /*
-         * Set new priority to that of highest priority
-         * task remaining in waitqueue.
+        /* Reset inh_task to NULL, and set flag indicating that you just
+         * released a PI semaphore.
          */
-        s->sem_prio = highest_prio;
-
-        /* Remove flag indicating that you should use semaphore priority. */
-        current->rt_param.has_resource = 0;
+        current->rt_param.inh_task = NULL;
+        current->rt_param.released_pi_sem = 1;
 }
 
 /**