linux-kernel - [PATCH V2] sched: skip autogroup when looking for all rt sched groups

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Date:	Tue, 28 Jun 2011 10:51:31 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Cheng Xu <chengxu@...ux.vnet.ibm.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>
Subject: [PATCH V2] sched: skip autogroup when looking for all rt sched groups

From: Yong Zhang <yong.zhang0@...il.com>
Subject: [PATCH V2] sched: skip autogroup when looking for all rt sched groups

Since [commit ec514c48: sched: Fix rt_rq runtime leakage bug],
'cat /proc/sched_debug' will print data of root_task_group.rt_rq
multi times, this is due to autogroup has no its own rt group,
instead rt group of autogroup is linked to root_task_group.

So skip it when we are looking for all rt sched groups, and it
will also save some noop operation against root_task_group when
__disable_runtime()/__enable_runtime().

V2: Based on Cheng Xu's idea which uses less code.

Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Mike Galbraith <efault@....de>
Cc: Cheng Xu <chengxu@...ux.vnet.ibm.com>
---

Attach it too in case webmail will mangle the patch.

 kernel/sched_autogroup.h |    1 +
 kernel/sched_rt.c        |   22 +++++++++++++++++-----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/kernel/sched_autogroup.h b/kernel/sched_autogroup.h
index 0557705..c2f0e72 100644
--- a/kernel/sched_autogroup.h
+++ b/kernel/sched_autogroup.h
@@ -13,6 +13,7 @@ struct autogroup {
 	int			nice;
 };

+static inline bool task_group_is_autogroup(struct task_group *tg);
 static inline struct task_group *
 autogroup_task_group(struct task_struct *p, struct task_group *tg);

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 10d0182..8c04cb2 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -185,11 +185,23 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)

 typedef struct task_group *rt_rq_iter_t;

-#define for_each_rt_rq(rt_rq, iter, rq) \
-	for (iter = list_entry_rcu(task_groups.next, typeof(*iter), list); \
-	     (&iter->list != &task_groups) && \
-	     (rt_rq = iter->rt_rq[cpu_of(rq)]); \
-	     iter = list_entry_rcu(iter->list.next, typeof(*iter), list))
+static inline struct task_group *next_task_group(struct task_group *tg)
+{
+	do {
+		tg = list_entry_rcu(tg->list.next,
+			typeof(struct task_group), list);
+	} while (&tg->list != &task_groups && task_group_is_autogroup(tg));
+
+	if (&tg->list == &task_groups)
+		tg = NULL;
+
+	return tg;
+}
+
+#define for_each_rt_rq(rt_rq, iter, rq)					\
+	for (iter = container_of(&task_groups, typeof(*iter), list);	\
+		(iter = next_task_group(iter)) &&			\
+		(rt_rq = iter->rt_rq[cpu_of(rq)]);)

 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
 {
-- 
1.7.4.1

View attachment "0001-sched-skip-autogroup-when-looking-for-all-rt-sched-g.patch" of type "text/x-patch" (2582 bytes)