I'm testing linux cpu hotpluging on normal 4-core ARM based on Android 8.1 kernel 4.4 sys. Problem seems that after onlining a CPU again taskset and kernel refuses to move and/or schedule any tasks on the core. E.g. doing:
echo 0 > /sys/devices/system/cpu/cpu3/online
echo 1 > /sys/devices/system/cpu/cpu3/online
taskset -c 3 bash
Fails... I don't know why taskset refuses to migrate any threads to the hotpluged cores. I have intend to use this to improve the kernel NO_HZ tickless operation by forcing Local timer interupts (LOC) off from cores 1-3. The kernel NO_HZ documentation suggests this possibility.
I also run it on upstream kernerl 4.18.4 on Linux qemu. it is also exist. please give me some help,thanks~
