From 175aed3f8d38b87d3287bb765c794205f2b511de Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 10 Dec 2014 15:55:08 -0800 Subject: [PATCH] exit: reparent: document the ->has_child_subreaper checks Swap the "init_task" and same_thread_group() checks. This way it is more simple to document these checks and we can remove the link to the previous discussion on lkml. Signed-off-by: Oleg Nesterov Cc: Aaron Tomlin Cc: "Eric W. Biederman" Cc: Kay Sievers Cc: Lennart Poettering Cc: Sterling Alexander Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index a4204aaba8a2..576949ce5665 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -495,18 +495,16 @@ static struct task_struct *find_new_reaper(struct task_struct *father) if (father->signal->has_child_subreaper) { struct task_struct *reaper; - /* - * Find the first ancestor marked as child_subreaper. - * Note that the code below checks same_thread_group(reaper, - * pid_ns->child_reaper). This is what we need to DTRT in a - * PID namespace. However we still need the check above, see - * http://marc.info/?l=linux-kernel&m=131385460420380 + * Find the first ->is_child_subreaper ancestor in our pid_ns. + * We start from father to ensure we can not look into another + * namespace, this is safe because all its threads are dead. */ for (reaper = father; - reaper != &init_task; + !same_thread_group(reaper, pid_ns->child_reaper); reaper = reaper->real_parent) { - if (same_thread_group(reaper, pid_ns->child_reaper)) + /* call_usermodehelper() descendants need this check */ + if (reaper == &init_task) break; if (!reaper->signal->is_child_subreaper) continue;