sched/rt: Try to restart rt period timer when rt runtime exceeded

hulk inclusion
category: bugfix
bugzilla: 185759 https://gitee.com/openeuler/kernel/issues/I4DDEL

---------------------------

When rt_runtime is modified from -1 to a valid control value, it may
cause the task to be throttled all the time. Operations like the following
will trigger the bug. E.g:
1. echo -1 > /proc/sys/kernel/sched_rt_runtime_us
2. Run a FIFO task named A that executes while(1)
3. echo 950000 > /proc/sys/kernel/sched_rt_runtime_us

When rt_runtime is -1, The rt period timer will not be activated when task A
enqueued. And then the task will be throttled after setting rt_runtime to
950,000. The task will always be throttled because the rt period timer is not
activated.
Signed-off-by: NLi Hua <hucool.lihua@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Reviewed-by: NCheng Jian <cj.chengjian@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

kernel/sched/rt.c

@@ -944,6 +944,18 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 	return rt_task_of(rt_se)->prio;
 }
 
+static inline void try_start_rt_bandwidth(struct rt_bandwidth *rt_b)
+{
+	raw_spin_lock(&rt_b->rt_runtime_lock);
+	if (!rt_b->rt_period_active) {
+		rt_b->rt_period_active = 1;
+		hrtimer_forward_now(&rt_b->rt_period_timer, rt_b->rt_period);
+		hrtimer_start_expires(&rt_b->rt_period_timer,
+				      HRTIMER_MODE_ABS_PINNED_HARD);
+	}
+	raw_spin_unlock(&rt_b->rt_runtime_lock);
+}
+
 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 {
 	u64 runtime = sched_rt_runtime(rt_rq);
@@ -1020,13 +1032,17 @@ static void update_curr_rt(struct rq *rq)
 
 	for_each_sched_rt_entity(rt_se) {
 		struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
+		int exceeded;
 
 		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 			raw_spin_lock(&rt_rq->rt_runtime_lock);
 			rt_rq->rt_time += delta_exec;
-			if (sched_rt_runtime_exceeded(rt_rq))
+			exceeded = sched_rt_runtime_exceeded(rt_rq);
+			if (exceeded)
 				resched_curr(rq);
 			raw_spin_unlock(&rt_rq->rt_runtime_lock);
+			if (exceeded)
+				try_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
 		}
 	}
 }
@@ -2721,8 +2737,10 @@ static int sched_rt_global_validate(void)
 
 static void sched_rt_do_global(void)
 {
+	raw_spin_lock(&def_rt_bandwidth.rt_runtime_lock);
 	def_rt_bandwidth.rt_runtime = global_rt_runtime();
 	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
+	raw_spin_unlock(&def_rt_bandwidth.rt_runtime_lock);
 }
 
 int sched_rt_handler(struct ctl_table *table, int write, void *buffer,