cgroup: Fix suspicious rcu_dereference_check() usage warning

commit f2aa197e upstream.

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
dc6e0818 ("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: dc6e0818 ("sched/cpuacct: Optimize away RCU read lock")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reported-by:  <syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20220305034103.57123-1-zhouchengming@bytedance.com


Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>