Hello, I am seeing -EBUSY returned a lot during torture_onoff() when running rcutorture on arm64. This causes hotplug failure 30% of the time. I am also seeing this in 6.1-rc kernels. I believe see this only for CPU0. This causes warnings in torture tests: [ 217.582290] rcu-torture:torture_onoff task: offline 0 failed: errno -16 [ 221.866362] rcu-torture:torture_onoff task: offline 0 failed: errno -16 Full kernel log here: http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/TREE04/console.log Any ideas on why this is happening and only for CPU 0 (presumably the boot CPU)? I'd personally need these warnings to go away for my tests as this causes rcutorture's tests to not cleanly pass for me. It appears remove_cpu() -> device_offline() is what returns the error. You can browse through all the torture test artifacts here which contains everything (build logs, vmlinux, etc). http://box.joelfernandes.org:9080/job/rcutorture_stable_arm/job/linux-5.15.y/7/artifact/tools/testing/selftests/rcutorture/res/2023.01.15-14.51.11/ Thanks for your help! - Joel
