rcu: Make task_subsys_state() RCU-lockdep checks handle boot-time use

It is apparently legal to invoke task_subsys_state() without RCU
protection during early boot time.  After all, there are no
concurrent tasks, so there can be no grace periods completing
concurrently.

But this does need an Acked-by from the cgroups folks.

Located-by: Ingo Molnar <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c9bbcb2a75ae..a73e1ced09b8 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -489,6 +489,7 @@ static inline struct cgroup_subsys_state *task_subsys_state(
 {
 	return rcu_dereference_check(task->cgroups->subsys[subsys_id],
 				     rcu_read_lock_held() ||
+				     !rcu_scheduler_active ||
 				     cgroup_lock_is_held());
 }