Killing all descendent processes robustly on macOS

Question

On Linux, Pid namespaces can be used to robustly kill all descendent (including orphaned & zombie) processes – see this answer for example.

What's the closest to a "robust" way to do the same on macOS? I can't rely on process groups unfortunately as some of the descendent processes alter them.

Answer 1

It's a gross kludge, but it might work: The first process would open a file descriptor so that, by default, all descendant processes inherit it. When it wants to kill them all, it runs lsof to find all processes with that file open and kills them.

Answer 2

It won't work for processes which have detached themselves, but you could walk the child process tree using proc_listchildpids() and send signals to each PID you obtain. There are probably some timing edge cases between checking a process's children and killing it - it could spawn more processes in this time. You could perhaps suspend all processes before listing their children and killing them. Processes whose parent has died should I think be reattached to their grandparent anyway though (I may be wrong on this) so in that case, as long as you keep calling proc_listchildpids() after sending each round of signals you should eventually end up in a steady state. (Ideally with no child processes left. But if they get into a really bad state [due to a kernel bug], some processes may be completely unkillable.)

proc_listchildpids() is declared in <libproc/libproc.h> .