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Subject[PATCH 4/5] exit: reparent: cleanup the usage of reparent_leader()
1. Now that reparent_leader() doesn't abuse ->sibling we can shift
list_move_tail() from reparent_leader() to forget_original_parent()
and turn it into a single list_splice_tail_init(). This also makes
BUG_ON(!list_empty()) and list_for_each_entry_safe() unnecessary.

2. This also allows to shift the same_thread_group() check, it looks
a bit more clear in the caller.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/exit.c | 22 +++++++++-------------
1 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 939e9fc..e3e7379 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -529,15 +529,7 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
static void reparent_leader(struct task_struct *father, struct task_struct *p,
struct list_head *dead)
{
- list_move_tail(&p->sibling, &p->real_parent->children);
-
- if (p->exit_state == EXIT_DEAD)
- return;
- /*
- * If this is a threaded reparent there is no need to
- * notify anyone anything has happened.
- */
- if (same_thread_group(p->real_parent, father))
+ if (unlikely(p->exit_state == EXIT_DEAD))
return;

/* We don't want people slaying init. */
@@ -568,7 +560,7 @@ static void forget_original_parent(struct task_struct *father)
exit_ptrace(father);
reaper = find_new_reaper(father);

- list_for_each_entry_safe(p, n, &father->children, sibling) {
+ list_for_each_entry(p, &father->children, sibling) {
for_each_thread(p, t) {
t->real_parent = reaper;
BUG_ON(!t->ptrace != (t->parent == father));
@@ -578,12 +570,16 @@ static void forget_original_parent(struct task_struct *father)
group_send_sig_info(t->pdeath_signal,
SEND_SIG_NOINFO, t);
}
- reparent_leader(father, p, &dead_children);
+ /*
+ * If this is a threaded reparent there is no need to
+ * notify anyone anything has happened.
+ */
+ if (!same_thread_group(reaper, father))
+ reparent_leader(father, p, &dead_children);
}
+ list_splice_tail_init(&father->children, &reaper->children);
write_unlock_irq(&tasklist_lock);

- BUG_ON(!list_empty(&father->children));
-
list_for_each_entry_safe(p, n, &dead_children, ptrace_entry) {
list_del_init(&p->ptrace_entry);
release_task(p);
--
1.5.5.1


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