Hi all, We encountered EINVAL when enabling cpuset in cgroupv2 when io_uring worker threads are running. Here are the steps to reproduce the failure on kernel 6.1.14: 1. Remove cpuset from subtree_control > for d in $(find /sys/fs/cgroup/ -maxdepth 1 -type d); do echo '-cpuset' | sudo tee -a $d/cgroup.subtree_control; done > cat /sys/fs/cgroup/cgroup.subtree_control cpu io memory pids 2. Run any applications that utilize the uring worker thread pool. I used https://github.com/cloudflare/cloudflare-blog/tree/master/2022-02-io_uring-worker-pool > cargo run -- -a -w 2 -t 2 3. Enabling cpuset will return EINVAL > echo '+cpuset' | sudo tee -a /sys/fs/cgroup/cgroup.subtree_control +cpuset tee: /sys/fs/cgroup/cgroup.subtree_control: Invalid argument We traced this down to task_can_attach that will return EINVAL when it encounters kthreads with PF_NO_SETAFFINITY, which io_uring worker threads have. This seems like an unexpected interaction when enabling cpuset for the subtrees that contain kthreads. We are currently considering a workaround to try to enable cpuset in root subtree_control before any io_uring applications can start, hence failure to enable cpuset is localized to only cgroup with io_uring kthreads. But this is cumbersome. Any suggestions would be very much appreciated. Thanks, Daniel.
