linux-kernel - Re: [PATCH RESEND v2] sched/deadline: fix rt runtime corrupt when dl refuse a smaller bandwidth

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Message-ID: <20150317022550.GC3953@kernel>
Date:	Tue, 17 Mar 2015 10:25:50 +0800
From:	Wanpeng Li <wanpeng.li@...ux.intel.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@....com>, linux-kernel@...r.kernel.org,
	Wanpeng Li <wanpeng.li@...ux.intel.com>
Subject: Re: [PATCH RESEND v2] sched/deadline: fix rt runtime corrupt when dl
 refuse a smaller bandwidth

Ping Ingo, ;-)
On Fri, Mar 13, 2015 at 03:28:00PM +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 verifying new bandwidth for deadline in advance.
>
>Acked-by: Juri Lelli <juri.lelli@....com>
>Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>---
> kernel/sched/core.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>index 97fe79c..e884909 100644
>--- a/kernel/sched/core.c
>+++ b/kernel/sched/core.c
>@@ -7815,7 +7815,7 @@ static int sched_rt_global_constraints(void)
> }
> #endif /* CONFIG_RT_GROUP_SCHED */
> 
>-static int sched_dl_global_constraints(void)
>+static int sched_dl_global_validate(void)
> {
> 	u64 runtime = global_rt_runtime();
> 	u64 period = global_rt_period();
>@@ -7916,11 +7916,11 @@ int sched_rt_handler(struct ctl_table *table, int write,
> 		if (ret)
> 			goto undo;
> 
>-		ret = sched_rt_global_constraints();
>+		ret = sched_dl_global_validate();
> 		if (ret)
> 			goto undo;
> 
>-		ret = sched_dl_global_constraints();
>+		ret = sched_rt_global_constraints();
> 		if (ret)
> 			goto undo;
> 
>-- 
>1.9.1
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