New Feature: Arbitrary deadlines.2012.2

Added support for arbitrary deadlines.

Constraint: Relative deadline must be >= exec cost.

Use: Set relative deadline in rt_task::rdeadline. Set value to 0
     to default to implicit deadlines.

Limitations: PFAIR not supported by this patch. PFAIR updated to
     reject tasks that do not have implicit deadlines.

1 files changed, 17 insertions, 10 deletions

diff --git a/litmus/litmus.c b/litmus/litmus.c
index 301390148d02..81384327e850 100644
--- a/litmus/litmus.c
+++ b/litmus/litmus.c
@@ -102,21 +102,25 @@ asmlinkage long sys_set_rt_task_param(pid_t pid, struct rt_task __user * param)
                 goto out_unlock;
         }
 
+        /* set relative deadline to be implicit if left unspecified */
+        if (tp.relative_deadline == 0)
+                tp.relative_deadline = tp.period;
+
         if (tp.exec_cost <= 0)
                 goto out_unlock;
         if (tp.period <= 0)
                 goto out_unlock;
         if (!cpu_online(tp.cpu))
                 goto out_unlock;
-        if (tp.period < tp.exec_cost)
+        if (min(tp.relative_deadline, tp.period) < tp.exec_cost) /*density check*/
         {
                 printk(KERN_INFO "litmus: real-time task %d rejected "
-                       "because wcet > period\n", pid);
+                       "because task density > 1.0\n", pid);
                 goto out_unlock;
         }
-        if (    tp.cls != RT_CLASS_HARD &&
-                tp.cls != RT_CLASS_SOFT &&
-                tp.cls != RT_CLASS_BEST_EFFORT)
+        if (tp.cls != RT_CLASS_HARD &&
+            tp.cls != RT_CLASS_SOFT &&
+            tp.cls != RT_CLASS_BEST_EFFORT)
         {
                 printk(KERN_INFO "litmus: real-time task %d rejected "
                                  "because its class is invalid\n", pid);
@@ -321,11 +325,14 @@ long litmus_admit_task(struct task_struct* tsk)
 
         BUG_ON(is_realtime(tsk));
 
-        if (get_rt_period(tsk) == 0 ||
-            get_exec_cost(tsk) > get_rt_period(tsk)) {
-                TRACE_TASK(tsk, "litmus admit: invalid task parameters "
-                           "(%lu, %lu)\n",
-                           get_exec_cost(tsk), get_rt_period(tsk));
+        if (get_rt_relative_deadline(tsk) == 0 ||
+            get_exec_cost(tsk) >
+                        min(get_rt_relative_deadline(tsk), get_rt_period(tsk)) ) {
+                TRACE_TASK(tsk,
+                        "litmus admit: invalid task parameters "
+                        "(e = %lu, p = %lu, d = %lu)\n",
+                        get_exec_cost(tsk), get_rt_period(tsk),
+                        get_rt_relative_deadline(tsk));
                 retval = -EINVAL;
                 goto out;
         }