Re: [PATCH cgroup/for-6.0-fixes] cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock

[Tejun Heo]

On Mon, Aug 15, 2022 at 01:27:38PM -1000, Tejun Heo wrote:
> Bringing up a CPU may involve creating new tasks which requires read-locking
> threadgroup_rwsem, so threadgroup_rwsem nests inside cpus_read_lock().
> However, cpuset's ->attach(), which may be called with thredagroup_rwsem
> write-locked, also wants to disable CPU hotplug and acquires
> cpus_read_lock(), leading to a deadlock.
> 
> Fix it by guaranteeing that ->attach() is always called with CPU hotplug
> disabled and removing cpus_read_lock() call from cpuset_attach().
> 
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>

Applied to cgroup/for-6.0-fixes w/ commit message and comment update
suggested by Xuewen and Fixes / stable tags added.

Thanks.

-- 
tejun