New system calls: pidfd_open() and close_range()

It's inherent in the semantics of the command: pkill (I'm assuming this was typo) kills some processes which are currently running and have certain attributes, namely, all it happens to find. This may include processes which were started after the pkill (and thus, very likely shouldn't have been killed by it) but it may as well not (they might be started such that pkill won't find them). Arguably, a pidfd_open in pkill would stop that from possibly killing processes it shouldn't ever have killed because they didn't match the specification. I didn't understand that.