On Sat, Mar 05, 2022 at 11:41:03AM +0800, Chengming Zhou wrote:
> 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
> dc6e0818bc9a ("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: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock")
> Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
> Reported-by: syzbot+16e3f2c77e7c5a0113f9@xxxxxxxxxxxxxxxxxxxxxxxxx
> Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> ---
> include/linux/cgroup.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 1e356c222756..0d1ada8968d7 100644
> --- a/include/linux/cgroup.h
> +++ b/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))
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Thanks.
--
tejun
