From a53b831549141aa060a8b54b76e3a42870d74cc0 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 10 Dec 2014 15:55:28 -0800 Subject: [PATCH] exit: pidns: fix/update the comments in zap_pid_ns_processes() The comments in zap_pid_ns_processes() are not clear, we need to explain how this code actually works. 1. "Ignore SIGCHLD" looks like optimization but it is not, we also need this for correctness. 2. The comment above sys_wait4() could tell more. EXIT_ZOMBIE child is only possible if it has exited before we ignored SIGCHLD. Or if it is traced from the parent namespace, but in this case it will be reaped by debugger after detach, sys_wait4() acts as a synchronization point. 3. The comment about TASK_DEAD (EXIT_DEAD in fact) children is outdated. Contrary to what it says we do not need to make sure they all go away after 0a01f2cc390e "pidns: Make the pidns proc mount/umount logic obvious". At the same time, we do need to wait for nr_hashed==init_pids, but the reasons are quite different and not obvious: setns(). Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Aaron Tomlin Cc: Pavel Emelyanov Cc: Serge Hallyn Cc: Sterling Alexander Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed