Re: [External] Re: [next] WARNING: suspicious RCU usage : include/linux/cgroup.h:494 suspicious rcu_dereference_check() usage

[Naresh Kamboju]

On Sat, 5 Mar 2022 at 06:27, Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> wrote:
>
> On 2022/3/5 4:28 上午, Zhouyi Zhou wrote:
> > Hi Paul
> >
> > Yes, your suggestion works!
> > Thank you for your guidance, this is the first time I ever did a
> > bisection, I gained greatly during this process!
>
> Hi Zhouyi, thanks for the bisection test.
> Could this patch solve RCU warning? I just tested on my machine and there
> is no RCU warning any more.

This patch solves the reported problem. The test link provided below [1].

Tested-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>

>
> 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))
>


--
Linaro LKFT
https://lkft.linaro.org
[1] https://lkft.validation.linaro.org/scheduler/job/4664565#L339