Any time we have two runqueues locked we use that as an opportunity to

synchronise niffies to the highest value as idle ticks may have artificially
kept niffies low on one CPU and the truth can only be later.

1 files changed, 18 insertions, 2 deletions

diff --git a/kernel/sched/MuQSS.c b/kernel/sched/MuQSS.c
index ec29bc0233ca..e0c847d76c3a 100644
--- a/kernel/sched/MuQSS.c
+++ b/kernel/sched/MuQSS.c
@@ -402,6 +402,19 @@ static inline struct rq *this_rq_lock(void)
 }
 
 /*
+ * Any time we have two runqueues locked we use that as an opportunity to
+ * synchronise niffies to the highest value as idle ticks may have artificially
+ * kept niffies low on one CPU and the truth can only be later.
+ */
+static inline void synchronise_niffies(struct rq *rq1, struct rq *rq2)
+{
+	if (rq1->niffies > rq2->niffies)
+		rq2->niffies = rq1->niffies;
+	else
+		rq1->niffies = rq2->niffies;
+}
+
+/*
  * double_rq_lock - safely lock two runqueues
  *
  * Note this does not disable interrupts like task_rq_lock,
@@ -432,6 +445,7 @@ static inline void double_rq_lock(struct rq *rq1, struct rq *rq2)
 		__acquire(rq2->lock);	/* Fake it out ;) */
 	} else
 		__double_rq_lock(rq1, rq2);
+	synchronise_niffies(rq1, rq2);
 }
 
 /*
@@ -462,6 +476,7 @@ static inline void lock_second_rq(struct rq *rq1, struct rq *rq2)
 		raw_spin_unlock(&rq1->lock);
 		__double_rq_lock(rq1, rq2);
 	}
+	synchronise_niffies(rq1, rq2);
 }
 
 static inline void lock_all_rqs(void)
@@ -489,11 +504,12 @@ static inline void unlock_all_rqs(void)
 }
 
 /* Specially nest trylock an rq */
-static inline bool trylock_rq(struct rq *rq)
+static inline bool trylock_rq(struct rq *this_rq, struct rq *rq)
 {
 	if (unlikely(!do_raw_spin_trylock(&rq->lock)))
 		return false;
 	spin_acquire(&rq->lock.dep_map, SINGLE_DEPTH_NESTING, 1, _RET_IP_);
+	synchronise_niffies(this_rq, rq);
 	return true;
 }
 
@@ -3492,7 +3508,7 @@ task_struct *earliest_deadline_task(struct rq *rq, int cpu, struct task_struct *
 
 		/* if (i) implies other_rq != rq */
 		if (i) {
-			if (unlikely(!trylock_rq(other_rq)))
+			if (unlikely(!trylock_rq(rq, other_rq)))
 				continue;
 			/* Need to reevaluate entries after locking */
 			entries = other_rq->sl->entries;