sched/rt: fix rt runtime corrupt when dl refuse a smaller bandwidth

Dl class will refuse the bandwidth being set to some value smaller than the currently allocated bandwidth in any of the root_domains through sched_rt_runtime_us and sched_rt_period_us. RT runtime will be set according to sched_rt_runtime_us before dl class verify if the new bandwidth is suitable in the case of !CONFIG_RT_GROUP_SCHED.

However, rt runtime will be corrupt if dl refuse the new bandwidth since there is no undo to reset the rt runtime to the old value.

This patch fix it by setting rt runtime after all kinds of rational checking in the case of !CONFIG_RT_GROUP_SCHED.

Signed-off-by Wanpeng Li <[email protected]>

---
kernel/sched/core.c | 30 ++++++++++++++++--------------

1 file changed, 16 insertions(+), 14 deletions(-)

kernel/sched/core.c +16 -14

index 2e7578a..355dde3 100644
@@ -7795,20 +7795,7 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
 #else /* !CONFIG_RT_GROUP_SCHED */
 static int sched_rt_global_constraints(void)
 {
-	unsigned long flags;
-	int i, ret = 0;
-
-	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
-	for_each_possible_cpu(i) {
-		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
-
-		raw_spin_lock(&rt_rq->rt_runtime_lock);
-		rt_rq->rt_runtime = global_rt_runtime();
-		raw_spin_unlock(&rt_rq->rt_runtime_lock);
-	}
-	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
-
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 

@@ -7890,6 +7877,21 @@ static int sched_rt_global_validate(void)
 
 static void sched_rt_do_global(void)
 {
+#ifndef CONFIG_RT_GROUP_SCHED
+	unsigned long flags;
+	int i;
+
+	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
+	for_each_possible_cpu(i) {
+		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
+
+		raw_spin_lock(&rt_rq->rt_runtime_lock);
+		rt_rq->rt_runtime = global_rt_runtime();
+		raw_spin_unlock(&rt_rq->rt_runtime_lock);
+	}
+	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
+#endif
+
 	def_rt_bandwidth.rt_runtime = global_rt_runtime();
 	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
 }

Signature · 1 line

1.9.1

Dl class will refuse the bandwidth being set to some value smaller than the currently allocated bandwidth in any of the root_domains through sched_rt_runtime_us and sched_rt_period_us. RT runtime will be set according to sched_rt_runtime_us before dl class verify if the new bandwidth is suitable in the case of !CONFIG_RT_GROUP_SCHED.

However, rt runtime will be corrupt if dl refuse the new bandwidth since there is no undo to reset the rt runtime to the old value.

This patch fix it by setting rt runtime after all kinds of rational checking in the case of !CONFIG_RT_GROUP_SCHED.

Signed-off-by Wanpeng Li <[email protected]>

---
 kernel/sched/core.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

kernel/sched/core.c +16 -14

index 2e7578a..355dde3 100644
@@ -7795,20 +7795,7 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
 #else /* !CONFIG_RT_GROUP_SCHED */
 static int sched_rt_global_constraints(void)
 {
-	unsigned long flags;
-	int i, ret = 0;
-
-	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
-	for_each_possible_cpu(i) {
-		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
-
-		raw_spin_lock(&rt_rq->rt_runtime_lock);
-		rt_rq->rt_runtime = global_rt_runtime();
-		raw_spin_unlock(&rt_rq->rt_runtime_lock);
-	}
-	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
-
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 

@@ -7890,6 +7877,21 @@ static int sched_rt_global_validate(void)
 
 static void sched_rt_do_global(void)
 {
+#ifndef CONFIG_RT_GROUP_SCHED
+	unsigned long flags;
+	int i;
+
+	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
+	for_each_possible_cpu(i) {
+		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
+
+		raw_spin_lock(&rt_rq->rt_runtime_lock);
+		rt_rq->rt_runtime = global_rt_runtime();
+		raw_spin_unlock(&rt_rq->rt_runtime_lock);
+	}
+	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
+#endif
+
 	def_rt_bandwidth.rt_runtime = global_rt_runtime();
 	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
 }

Hi,

Quoted 6 lines · Wanpeng Li

Dl class will refuse the bandwidth being set to some value smaller than the currently allocated bandwidth in any of the root_domains through sched_rt_runtime_us and sched_rt_period_us. RT runtime will be set according to sched_rt_runtime_us before dl class verify if the new bandwidth is suitable in the case of !CONFIG_RT_GROUP_SCHED.

Quoted 3 lines

However, rt runtime will be corrupt if dl refuse the new bandwidth since there is no undo to reset the rt runtime to the old value.

Can't we just move sched_dl_global_constraints() before sched_rt_global_constraints(), and change the name of the former to sched_dl_global_validate() ?

Thanks,

- Juri

Quoted 57 lines

This patch fix it by setting rt runtime after all kinds of rational checking in the case of !CONFIG_RT_GROUP_SCHED.

Signed-off-by Wanpeng Li <[email protected]>

---
 kernel/sched/core.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

kernel/sched/core.c +16 -14

index 2e7578a..355dde3 100644
@@ -7795,20 +7795,7 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
 #else /* !CONFIG_RT_GROUP_SCHED */
 static int sched_rt_global_constraints(void)
 {
-	unsigned long flags;
-	int i, ret = 0;
-
-	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
-	for_each_possible_cpu(i) {
-		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
-
-		raw_spin_lock(&rt_rq->rt_runtime_lock);
-		rt_rq->rt_runtime = global_rt_runtime();
-		raw_spin_unlock(&rt_rq->rt_runtime_lock);
-	}
-	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
-
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_RT_GROUP_SCHED */
 

@@ -7890,6 +7877,21 @@ static int sched_rt_global_validate(void)
 
 static void sched_rt_do_global(void)
 {
+#ifndef CONFIG_RT_GROUP_SCHED
+	unsigned long flags;
+	int i;
+
+	raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
+	for_each_possible_cpu(i) {
+		struct rt_rq *rt_rq = &cpu_rq(i)->rt;
+
+		raw_spin_lock(&rt_rq->rt_runtime_lock);
+		rt_rq->rt_runtime = global_rt_runtime();
+		raw_spin_unlock(&rt_rq->rt_runtime_lock);
+	}
+	raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
+#endif
+
 	def_rt_bandwidth.rt_runtime = global_rt_runtime();
 	def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
 }