On Wed, Apr 03, 2024 at 04:26:38PM +0200, Valentin Schneider <vschneid@xxxxxxxxxx> wrote: > Also, I gave Michal's patch a try and it looks like it's introducing a Thank you. > cgroup_threadgroup_rwsem -> cpuset_mutex > ordering from > cgroup_transfer_tasks_locked() > `\ > percpu_down_write(&cgroup_threadgroup_rwsem); > cgroup_migrate() > `\ > cgroup_migrate_execute() > `\ > ss->can_attach() // cpuset_can_attach() > `\ > mutex_lock(&cpuset_mutex); > > which is invalid, see below. _This_ should be the right order (cpuset_mutex inside cgroup_threadgroup_rwsem), at least in my mental model. Thus I missed that cpuset_mutex must have been taken somewhere higher up in the hotplug code (CPU 0 in the lockdep dump, I can't easily see where from) :-/. Michal
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