From e593c9dbe858c82e284ff85e625837ae3ab32f1c Mon Sep 17 00:00:00 2001
From: "Bjoern B. Brandenburg" <bbb@cs.unc.edu>
Date: Fri, 28 Jan 2011 19:04:08 -0500
Subject: EDF: support priority boosting

While we are at it, simplify edf_higher_prio() a bit.
---
 include/litmus/litmus.h   |  3 +++
 include/litmus/rt_param.h |  7 +++++++
 litmus/edf_common.c       | 38 +++++++++++++++++++++++++++-----------
 3 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/include/litmus/litmus.h b/include/litmus/litmus.h
index 8971b25f23e6..b38d39a7461d 100644
--- a/include/litmus/litmus.h
+++ b/include/litmus/litmus.h
@@ -54,6 +54,9 @@ void litmus_exit_task(struct task_struct *tsk);
 #define get_release(t)		(tsk_rt(t)->job_params.release)
 #define get_class(t)		(tsk_rt(t)->task_params.cls)
 
+#define is_priority_boosted(t)	(tsk_rt(t)->priority_boosted)
+#define get_boost_start(t)	(tsk_rt(t)->boost_start_time)
+
 inline static int budget_exhausted(struct task_struct* t)
 {
 	return get_exec_time(t) >= get_exec_cost(t);
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index a7a183f34a80..5de422c742f6 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -108,6 +108,13 @@ struct rt_param {
 	/* is the task present? (true if it can be scheduled) */
 	unsigned int		present:1;
 
+#ifdef CONFIG_LITMUS_LOCKING
+	/* Is the task being priority-boosted by a locking protocol? */
+	unsigned int		priority_boosted:1;
+	/* If so, when did this start? */
+	lt_t			boost_start_time;
+#endif
+
 	/* user controlled parameters */
 	struct rt_task 		task_params;
 
diff --git a/litmus/edf_common.c b/litmus/edf_common.c
index 06daec66c984..9b44dc2d8d1e 100644
--- a/litmus/edf_common.c
+++ b/litmus/edf_common.c
@@ -33,22 +33,38 @@ int edf_higher_prio(struct task_struct* first,
 	}
 
 
+	/* check for NULL tasks */
+	if (!first || !second)
+		return first && !second;
+
+#ifdef CONFIG_LITMUS_LOCKING
+
 	/* Check for inherited priorities. Change task
 	 * used for comparison in such a case.
 	 */
-	if (first && first->rt_param.inh_task)
+	if (unlikely(first->rt_param.inh_task))
 		first_task = first->rt_param.inh_task;
-	if (second && second->rt_param.inh_task)
+	if (unlikely(second->rt_param.inh_task))
 		second_task = second->rt_param.inh_task;
 
-	return
-		/* it has to exist in order to have higher priority */
-		first_task && (
-		/* does the second task exist and is it a real-time task?  If
-		 * not, the first task (which is a RT task) has higher
-		 * priority.
-		 */
-		!second_task || !is_realtime(second_task)  ||
+	/* Check for priority boosting. Tie-break by start of boosting.
+	 */
+	if (unlikely(is_priority_boosted(first_task))) {
+		/* first_task is boosted, how about second_task? */
+		if (!is_priority_boosted(second_task) ||
+		    lt_before(get_boost_start(first_task),
+			      get_boost_start(second_task)))
+			return 1;
+		else
+			return 0;
+	} else if (unlikely(is_priority_boosted(second_task)))
+		/* second_task is boosted, first is not*/
+		return 0;
+
+#endif
+
+
+	return !is_realtime(second_task)  ||
 
 		/* is the deadline of the first task earlier?
 		 * Then it has higher priority.
@@ -65,7 +81,7 @@ int edf_higher_prio(struct task_struct* first,
 		 * priority wins.
 		 */
 		(first_task->pid == second_task->pid &&
-		 !second->rt_param.inh_task))));
+		 !second->rt_param.inh_task)));
 }
 
 int edf_ready_order(struct bheap_node* a, struct bheap_node* b)
-- 
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