linux-kernel - Re: [PATCH] cgroup/cpu: Fix tg_has_rt

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Date:   Tue, 20 Sep 2016 15:41:09 -0400
From:   Tejun Heo <tj@...nel.org>
To:     yingooyim <ygyim@...kuk.ac.kr>
Cc:     lizefan@...wei.com, hannes@...xchg.org, cgroups@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, jinh@...kuk.ac.kr
Subject: Re: [PATCH] cgroup/cpu: Fix tg_has_rt_task() malfunction

On Sun, Sep 18, 2016 at 11:23:10PM +0900, yingooyim wrote:
> Hi,
> I am a graduate student of System Software Lab. at Konkuk University
> (http://sslab.konkuk.ac.kr).
> 
> This patch is to fix the malfunction of tg_has_rt_tasks(). The
> tg_has_rt_tasks() function is supposed to determine whether a task
> group includes an "rt task" or not. However, it returns true for
> "dl task" too. The origin of this problem is that rt_task() called
> by tg_has_rt_tasks() returns true for dl tasks. Because of this
> problem, tg_rt_schedulable() that calls tg_has_rt_tasks() returns
> –EBUSY if we try to initialize an rt task group, while a dl task
> is running. That is, you cannot run an rt task group when there
> exists a dl task in the system. Our patch provided in this post
> simply makes the tg_has_rt_tasks() function return false for dl
> tasks by calling dl_task() in the conditional statement.
> 
> Previously we have provided another patch for rt_task() (more
> precisely rt_prio()) to resolve this problem as follows:
> https://patchwork.kernel.org/patch/9299267/
> However, a dependency issue were raised. So, we think that it is
> better to modify tg_has_rt_tasks() instead of rt_task() itself.
> 
> Signed-off-by: Yin-goo Yim <ygyim@...kuk.ac.kr>

Can you please repost with scheduler maintainers cc'd?

 Ingo Molnar <mingo@...hat.com>
 Peter Zijlstra <peterz@...radead.org>

Thanks.

-- 
tejun