> when the orphan terminates, it is the subreaper process that will receive a SIGCHLD signal and will be able to wait(2) on the process to discover its termination status
Seems like you don’t need a dedicated “always alive” thread if it’s being delivered to the process and tokio automatically does masking for threads so that you register for listening to signals using it’s asynchronous mechanisms & don’t have issues around signal safety which it abstracts away for you (i.e. as long as you’re handling the SIGCHILD signal somewhere or even just ignoring it as I don’t think they actually care?).
That being said, it’s not clear PR_SET_CHILD_SUBREAPER actually causes grand children to be killed when the reaper process dies which is the effect they’re looking for here (not the reverse where you reap forked children as they die). So you may need to spawn a dedicated reaper process rather than thread to manage the lifetime of children which is much more complicated.
> That being said, it’s not clear PR_SET_CHILD_SUBREAPER actually causes grand children to be killed when the reaper process dies
CHILD_SUBREAPER kills neither children nor grandchildren. It's effect is in the other direction, inteded for sub-service-managers that want to keep track of all children. If the subreaper dies, children are reparented to the next subreaper up (or init).
Yeah, I was assuming they have something calling `wait` somewhere since they say "HyperQueue is essentially a process manager", and to me "process manager" implies pretty strongly "spawns and waits for processes".
Seems like you don’t need a dedicated “always alive” thread if it’s being delivered to the process and tokio automatically does masking for threads so that you register for listening to signals using it’s asynchronous mechanisms & don’t have issues around signal safety which it abstracts away for you (i.e. as long as you’re handling the SIGCHILD signal somewhere or even just ignoring it as I don’t think they actually care?).
That being said, it’s not clear PR_SET_CHILD_SUBREAPER actually causes grand children to be killed when the reaper process dies which is the effect they’re looking for here (not the reverse where you reap forked children as they die). So you may need to spawn a dedicated reaper process rather than thread to manage the lifetime of children which is much more complicated.