4 files changed, 28 insertions, 10 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 46a2345..b53cc85 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -119,7 +119,9 @@ void update_rq_clock(struct rq *rq)
 {
 	s64 delta;
 
-	if (rq->skip_clock_update > 0)
+	lockdep_assert_held(&rq->lock);
+
+	if (rq->clock_skip_update & RQCF_ACT_SKIP)
 		return;
 
 	delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
@@ -1046,7 +1048,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
 	 * this case, we can save a useless back to back clock update.
 	 */
 	if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
-		rq->skip_clock_update = 1;
+		rq_clock_skip_update(rq, true);
 }
 
 #ifdef CONFIG_SMP
@@ -2779,6 +2781,8 @@ need_resched:
 	smp_mb__before_spinlock();
 	raw_spin_lock_irq(&rq->lock);
 
+	rq->clock_skip_update <<= 1; /* promote REQ to ACT */
+
 	switch_count = &prev->nivcsw;
 	if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
 		if (unlikely(signal_pending_state(prev->state, prev))) {
@@ -2803,13 +2807,13 @@ need_resched:
 		switch_count = &prev->nvcsw;
 	}
 
-	if (task_on_rq_queued(prev) || rq->skip_clock_update < 0)
+	if (task_on_rq_queued(prev))
 		update_rq_clock(rq);
 
 	next = pick_next_task(rq, prev);
 	clear_tsk_need_resched(prev);
 	clear_preempt_need_resched();
-	rq->skip_clock_update = 0;
+	rq->clock_skip_update = 0;
 
 	if (likely(prev != next)) {
 		rq->nr_switches++;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 50ff902..2ecf779 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5156,7 +5156,7 @@ static void yield_task_fair(struct rq *rq)
 		 * so we don't do microscopic update in schedule()
 		 * and double the fastpath cost.
 		 */
-		 rq->skip_clock_update = 1;
+		rq_clock_skip_update(rq, true);
 	}
 
 	set_skip_buddy(se);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index ee15f5a..6725e3c 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -831,11 +831,14 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 				enqueue = 1;
 
 				/*
-				 * Force a clock update if the CPU was idle,
-				 * lest wakeup -> unthrottle time accumulate.
+				 * When we're idle and a woken (rt) task is
+				 * throttled check_preempt_curr() will set
+				 * skip_update and the time between the wakeup
+				 * and this unthrottle will get accounted as
+				 * 'runtime'.
 				 */
 				if (rt_rq->rt_nr_running && rq->curr == rq->idle)
-					rq->skip_clock_update = -1;
+					rq_clock_skip_update(rq, false);
 			}
 			if (rt_rq->rt_time || rt_rq->rt_nr_running)
 				idle = 0;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bd23732..0870db2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -558,8 +558,6 @@ struct rq {
 #ifdef CONFIG_NO_HZ_FULL
 	unsigned long last_sched_tick;
 #endif
-	int skip_clock_update;
-
 	/* capture load from *all* tasks on this cpu: */
 	struct load_weight load;
 	unsigned long nr_load_updates;
@@ -588,6 +586,7 @@ struct rq {
 	unsigned long next_balance;
 	struct mm_struct *prev_mm;
 
+	unsigned int clock_skip_update;
 	u64 clock;
 	u64 clock_task;
 
@@ -704,6 +703,18 @@ static inline u64 rq_clock_task(struct rq *rq)
 	return rq->clock_task;
 }
 
+#define RQCF_REQ_SKIP	0x01
+#define RQCF_ACT_SKIP	0x02
+
+static inline void rq_clock_skip_update(struct rq *rq, bool skip)
+{
+	lockdep_assert_held(&rq->lock);
+	if (skip)
+		rq->clock_skip_update |= RQCF_REQ_SKIP;
+	else
+		rq->clock_skip_update &= ~RQCF_REQ_SKIP;
+}
+
 #ifdef CONFIG_NUMA
 enum numa_topology_type {
 	NUMA_DIRECT,