[PATCH 3/5] sched: Fix an RCU warning in print_task()

Li Zefan
2010-04-22T09:28:54Z

With CONFIG_PROVE_RCU=y, a warning can be triggered:

$ cat /proc/sched_debug

...
kernel/cgroup.c:1649 invoked rcu_dereference_check() without protection!
...

Both cgroup_path() and task_group() should be called with either
rcu_read_lock or cgroup_mutex held.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/sched_debug.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 9cf1baf..87a330a 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -114,7 +114,9 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
{
char path[64];

+ rcu_read_lock();
cgroup_path(task_group(p)->css.cgroup, path, sizeof(path));
+ rcu_read_unlock();
SEQ_printf(m, " %s", path);
}
#endif
--
1.6.3