From mboxrd@z Thu Jan 1 00:00:00 1970 From: "yingooyim" Subject: [PATCH] cgroup/cpu: Fix tg_has_rt_task() malfunction Date: Sun, 18 Sep 2016 23:23:10 +0900 Message-ID: <1474208588556845.0.mail@mail> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; format="flowed"; charset="windows-1252"; reply-type="original" To: tj@kernel.org, lizefan@huawei.com, hannes@cmpxchg.org Cc: cgroups@vger.kernel.org, LKML , jinh@konkuk.ac.kr 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 =E2=80=93EBUSY 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 ---- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2a906f2..ee5ab2f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7846,7 +7846,7 @@ static inline int tg_has_rt_tasks(struct task_group=20 *tg) return 0; for_each_process_thread(g, p) { - if (rt_task(p) && task_group(p) =3D=3D tg) + if (rt_task(p) && !dl_task(p) && task_group(p) =3D=3D tg) return 1; }