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

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Message-ID: <54EEED7C.2030504@arm.com>
Date:	Thu, 26 Feb 2015 09:55:08 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"juri.lelli@...il.com" <juri.lelli@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND v2] sched/deadline: fix rt runtime corrupt when
 dl refuse a smaller bandwidth

Hi,

On 25/02/2015 04:37, 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.
> 

Looks good, thanks!

Acked-by: Juri Lelli <juri.lelli@....com>

> Cc: Juri Lelli <juri.lelli@....com>
> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
> ---
> v1 -> v2:
>  * move sched_dl_global_constraints before sched_rt_global_constraints,
>    and change the name of the former to sched_dl_global_validate().
> 
>  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;
>  
> 

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