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exit: reparent: cleanup the usage of reparent_leader()

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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>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Cc: Sterling Alexander <stalexan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@hack.frob.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-12-10 15:45:30 -08:00 committed by Linus Torvalds
parent 57a059187d
commit 2831096e21
1 changed files with 9 additions and 13 deletions
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22
kernel/exit.c
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@ -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);