Re: [PATCH 3/3] cgroup/cpuset: Allow only one active attach operation per cpuset

[Waiman Long]

On 4/4/23 05:07, Michal Koutný wrote:
> Hi.
>
> On Mon, Apr 03, 2023 at 01:41:33PM -0400, Waiman Long <longman@xxxxxxxxxx> wrote:
> > This patch is actually not related to the CLONE_INTO_GROUP problem in patch
> > 1. It is a generic problem when multiple users are moving threads into
> > cgroup.threads of the same or different cpusets simultaneously.
> I meant this:
> 	__cgroup_procs_write
> 	  cgroup_kn_lock_live
> 	    mutex_lock(&cgroup_mutex)
>
> and (more succintly)
> 	cgroup_update_dfl_csses
> 	  lockdep_assert_held(&cgroup_mutex)
>
> Even the threaded migrations should be synchronized here.
> Can you please explain in more detail what's the problematic case?

You are right. I missed the cgroup_mutex synchronization here. So this 
patch isn't needed. I will drop it in the next version.

Cheers,
Longman