My friend was running firefox on linux mint, and it froze and he used xkill to kill firefox. But still it shows up in htop ps -aux. He tried to kill it multiple times but it didn’t work. See the pictures for explanation. We had to kill power to shutdown, even systemd can’t stop that process.
Yes, I killed the parent process. Also after killing the process with firefox PID, the file equivalent to that process
/proc/PIDwas still there. I think it could be - “likely I/O or driver related” or “stuck in a syscall waiting on some kind of I/O operation that isn’t timing out/is bugged out/can never complete”.