linux-kernel - Re: [PATCH] sched/rt: fix rt runtime corrupt when dl refuse a smaller bandwidth

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Date:	Tue, 18 Nov 2014 10:21:13 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Kirill Tkhai <ktkhai@...allels.com>,
	linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH] sched/rt: fix rt runtime corrupt when dl refuse a
 smaller bandwidth

Ping Juri, ;-)
On Thu, Nov 13, 2014 at 04:47:39PM +0800, Wanpeng Li wrote:
>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 <wanpeng.li@...ux.intel.com>
>---
> kernel/sched/core.c | 30 ++++++++++++++++--------------
> 1 file changed, 16 insertions(+), 14 deletions(-)
>
>diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>index 2e7578a..355dde3 100644
>--- a/kernel/sched/core.c
>+++ b/kernel/sched/core.c
>@@ -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());
> }
>-- 
>1.9.1
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