cgroups: make cgroup_path() RCU-safe

Fix races between /proc/sched_debug by freeing cgroup objects via an RCU
callback.  Thus any cgroup reference obtained from an RCU-safe source will
remain valid during the RCU section.  Since dentries are also RCU-safe,
this allows us to traverse up the tree safely.

Additionally, make cgroup_path() check for a NULL cgrp->dentry to avoid
trying to report a path for a partially-created cgroup.

[[email protected]: call deactive_super() in cgroup_diput()]
Signed-off-by: Paul Menage <[email protected]>
Reviewed-by: Li Zefan <[email protected]>
Tested-by: Li Zefan <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Li Zefan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions