From d0679a7100b30c9da2e7cb9a65b5edb0d09faaf9 Mon Sep 17 00:00:00 2001
From: Paul Turner <pjt@google.com>
Date: Thu, 21 Jul 2011 09:43:35 -0700
Subject: [PATCH] --- yaml --- r: 269151 b: refs/heads/master c:
 8277434ef1202ce30315f8edb3fc760aa6e74493 h: refs/heads/master i:   269149:
 d9b0ee1377ce77a4bea6e0b2ad8cafd9f25fac2f   269147:
 202eebda3821ce64579380a345475c2fb1408d2b   269143:
 9920b2a12fb81998a3e66e9d825c9ac4b1a42e00   269135:
 fedc0871392a731c65266faab6de1675bd0191be   269119:
 b1bb01111fae15b563db4fd83f8411665cf7cfc2 v: v3

---
 [refs]               |  2 +-
 trunk/kernel/sched.c | 50 ++++++++++++++++++++++++++++++++------------
 2 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/[refs] b/[refs]
index 4f0f8ace4926..de07727df0a0 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 671fd9dabe5239ad218c7eb48b2b9edee50250e6
+refs/heads/master: 8277434ef1202ce30315f8edb3fc760aa6e74493
diff --git a/trunk/kernel/sched.c b/trunk/kernel/sched.c
index 4bbabc2c4a77..8ec1e7ac2894 100644
--- a/trunk/kernel/sched.c
+++ b/trunk/kernel/sched.c
@@ -1591,20 +1591,23 @@ static inline void dec_cpu_load(struct rq *rq, unsigned long load)
 typedef int (*tg_visitor)(struct task_group *, void *);
 
 /*
- * Iterate the full tree, calling @down when first entering a node and @up when
- * leaving it for the final time.
+ * Iterate task_group tree rooted at *from, calling @down when first entering a
+ * node and @up when leaving it for the final time.
+ *
+ * Caller must hold rcu_lock or sufficient equivalent.
  */
-static int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
+static int walk_tg_tree_from(struct task_group *from,
+			     tg_visitor down, tg_visitor up, void *data)
 {
 	struct task_group *parent, *child;
 	int ret;
 
-	rcu_read_lock();
-	parent = &root_task_group;
+	parent = from;
+
 down:
 	ret = (*down)(parent, data);
 	if (ret)
-		goto out_unlock;
+		goto out;
 	list_for_each_entry_rcu(child, &parent->children, siblings) {
 		parent = child;
 		goto down;
@@ -1613,19 +1616,29 @@ static int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
 		continue;
 	}
 	ret = (*up)(parent, data);
-	if (ret)
-		goto out_unlock;
+	if (ret || parent == from)
+		goto out;
 
 	child = parent;
 	parent = parent->parent;
 	if (parent)
 		goto up;
-out_unlock:
-	rcu_read_unlock();
-
+out:
 	return ret;
 }
 
+/*
+ * Iterate the full tree, calling @down when first entering a node and @up when
+ * leaving it for the final time.
+ *
+ * Caller must hold rcu_lock or sufficient equivalent.
+ */
+
+static inline int walk_tg_tree(tg_visitor down, tg_visitor up, void *data)
+{
+	return walk_tg_tree_from(&root_task_group, down, up, data);
+}
+
 static int tg_nop(struct task_group *tg, void *data)
 {
 	return 0;
@@ -8870,13 +8883,19 @@ static int tg_rt_schedulable(struct task_group *tg, void *data)
 
 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
 {
+	int ret;
+
 	struct rt_schedulable_data data = {
 		.tg = tg,
 		.rt_period = period,
 		.rt_runtime = runtime,
 	};
 
-	return walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
+	rcu_read_lock();
+	ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
+	rcu_read_unlock();
+
+	return ret;
 }
 
 static int tg_set_rt_bandwidth(struct task_group *tg,
@@ -9333,6 +9352,7 @@ static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
 
 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
 {
+	int ret;
 	struct cfs_schedulable_data data = {
 		.tg = tg,
 		.period = period,
@@ -9344,7 +9364,11 @@ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
 		do_div(data.quota, NSEC_PER_USEC);
 	}
 
-	return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
+	rcu_read_lock();
+	ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
+	rcu_read_unlock();
+
+	return ret;
 }
 #endif /* CONFIG_CFS_BANDWIDTH */
 #endif /* CONFIG_FAIR_GROUP_SCHED */