Task Control Groups: add tasks file interface

Add the per-directory "tasks" file for cgroupfs mounts; this allows the
user to determine which tasks are members of a cgroup by reading a
cgroup's "tasks", and to move a task into a cgroup by writing its pid to
its "tasks".

Signed-off-by: Paul Menage <[email protected]>
Cc: Serge E. Hallyn <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Paul Jackson <[email protected]>
Cc: Kirill Korotaev <[email protected]>
Cc: Herbert Poetzl <[email protected]>
Cc: Srivatsa Vaddagiri <[email protected]>
Cc: Cedric Le Goater <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 60735dcf427a..e2dd44f68f97 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -144,6 +144,16 @@ int cgroup_is_removed(const struct cgroup *cont);
 
 int cgroup_path(const struct cgroup *cont, char *buf, int buflen);
 
+int __cgroup_task_count(const struct cgroup *cont);
+static inline int cgroup_task_count(const struct cgroup *cont)
+{
+	int task_count;
+	rcu_read_lock();
+	task_count = __cgroup_task_count(cont);
+	rcu_read_unlock();
+	return task_count;
+}
+
 /* Return true if the cgroup is a descendant of the current cgroup */
 int cgroup_is_descendant(const struct cgroup *cont);