Adapt FMLP+ priority boosting order in P-FP plugin.

Generic priority-points also clear the way for xPCP variants.

1 files changed, 13 insertions, 11 deletions

diff --git a/litmus/sched_pfp.c b/litmus/sched_pfp.c
index c98429938033..45c838f1413e 100644
--- a/litmus/sched_pfp.c
+++ b/litmus/sched_pfp.c
@@ -325,19 +325,19 @@ static void pfp_task_exit(struct task_struct * t)
 #include <litmus/fdso.h>
 #include <litmus/srp.h>
 
-static void boost_priority(struct task_struct* t)
+static void boost_priority(struct task_struct* t, lt_t priority_point)
 {
         unsigned long           flags;
         pfp_domain_t*   pfp = task_pfp(t);
-        lt_t                    now;
 
         raw_spin_lock_irqsave(&pfp->slock, flags);
-        now = litmus_clock();
+
 
         TRACE_TASK(t, "priority boosted at %llu\n", now);
 
         tsk_rt(t)->priority_boosted = 1;
-        tsk_rt(t)->boost_start_time = now;
+        /* tie-break by protocol-specific priority point */
+        tsk_rt(t)->boost_start_time = priority_point;
 
         if (pfp->scheduled != t) {
                 /* holder may be queued: first stop queue changes */
@@ -411,12 +411,20 @@ int pfp_fmlp_lock(struct litmus_lock* l)
         struct fmlp_semaphore *sem = fmlp_from_lock(l);
         wait_queue_t wait;
         unsigned long flags;
+        lt_t time_of_request;
 
         if (!is_realtime(t))
                 return -EPERM;
 
         spin_lock_irqsave(&sem->wait.lock, flags);
 
+        /* tie-break by this point in time */
+        time_of_request = litmus_clock();
+
+        /* Priority-boost ourself *before* we suspend so that
+         * our priority is boosted when we resume. */
+        boost_priority(t, time_of_request);
+
         if (sem->owner) {
                 /* resource is not free => must suspend and wait */
 
@@ -449,9 +457,6 @@ int pfp_fmlp_lock(struct litmus_lock* l)
                 /* it's ours now */
                 sem->owner = t;
 
-                /* mark the task as priority-boosted. */
-                boost_priority(t);
-
                 spin_unlock_irqrestore(&sem->wait.lock, flags);
         }
 
@@ -479,13 +484,10 @@ int pfp_fmlp_unlock(struct litmus_lock* l)
         /* check if there are jobs waiting for this resource */
         next = __waitqueue_remove_first(&sem->wait);
         if (next) {
-                /* boost next job */
-                boost_priority(next);
-
                 /* next becomes the resouce holder */
                 sem->owner = next;
 
-                /* wake up next */
+                /* Wake up next. The waiting job is already priority-boosted. */
                 wake_up_process(next);
         } else
                 /* resource becomes available */