cgroup: Fix suspicious rcu_dereference_check() usage warning

task_css_set_check() will use rcu_dereference_check() to check for
rcu_read_lock_held() on the read-side, which is not true after commit
dc6e081 ("sched/cpuacct: Optimize away RCU read lock"). This
commit drop explicit rcu_read_lock(), change to RCU-sched read-side
critical section. So fix the RCU warning by adding check for
rcu_read_lock_sched_held().

Fixes: dc6e081 ("sched/cpuacct: Optimize away RCU read lock")
Reported-by: Linux Kernel Functional Testing <[email protected]>
Reported-by: [email protected]
Signed-off-by: Chengming Zhou <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Tested-by: Zhouyi Zhou <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Chengming Zhou

include/linux/cgroup.h

@@ -450,6 +450,7 @@ extern struct mutex cgroup_mutex;
 extern spinlock_t css_set_lock;
 #define task_css_set_check(task, __c)					\
 	rcu_dereference_check((task)->cgroups,				\
+		rcu_read_lock_sched_held() ||				\
 		lockdep_is_held(&cgroup_mutex) ||			\
 		lockdep_is_held(&css_set_lock) ||			\
 		((task)->flags & PF_EXITING) || (__c))