sched: group scheduling, minor fixes

Minor bug fixes for the group scheduler:

- Use a mutex to serialize add/remove of task groups and also when
  changing shares of a task group. Use the same mutex when printing
  cfs_rq debugging stats for various task groups.

- Use list_for_each_entry_rcu in for_each_leaf_cfs_rq macro (when
  walking task group list)

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index da7c061e720..0c5fdce6722 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -690,7 +690,7 @@ static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
 
 /* Iterate thr' all leaf cfs_rq's on a runqueue */
 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
-        list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
+        list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
 
 /* Do the two (enqueued) entities belong to the same group ? */
 static inline int
@@ -1132,7 +1132,9 @@ static void print_cfs_stats(struct seq_file *m, int cpu)
 #ifdef CONFIG_FAIR_GROUP_SCHED
         print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs);
 #endif
+        lock_task_group_list();
         for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
                 print_cfs_rq(m, cpu, cfs_rq);
+        unlock_task_group_list();
 }
 #endif