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Subject[PATCH 4/6] 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 <oleg@redhat.com>
---
kernel/exit.c | 14 ++++++--------
1 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index ac7ba9b..266e4f4 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;
--
1.5.5.1


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