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forget_original_parent: do not abuse child->ptrace_entry 

By discussion with Roland.

- Use ->sibling instead of ->ptrace_entry to chain the need to be
  release_task'd childs. Nobody else can use ->sibling, this task
  is EXIT_DEAD and nobody can find it on its own list.

- rename ptrace_dead to dead_childs.

- Now that we don't have the "parallel" untrace code, change back
  reparent_thread() to return void, pass dead_childs as an argument.

Actually, I don't understand why do we notify /sbin/init when we
reparent a zombie, probably it is better to reap it unconditionally.

[akpm@linux-foundation.org: s/childs/children/]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: Roland McGrath <roland@redhat.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 2009-04-02 16:58:19 -07:00 committed by Linus Torvalds
parent 39c626ae47
commit 5dfc80be73
1 changed files with 41 additions and 46 deletions
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87
kernel/exit.c
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@ -726,46 +726,6 @@ static void exit_mm(struct task_struct * tsk)
mmput(mm);
}
/* Returns nonzero if the child should be released. */
static int reparent_thread(struct task_struct *p, struct task_struct *father)
{
int dead;
if (p->pdeath_signal)
/* We already hold the tasklist_lock here. */
group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
list_move_tail(&p->sibling, &p->real_parent->children);
if (task_detached(p))
return 0;
/* If this is a threaded reparent there is no need to
* notify anyone anything has happened.
*/
if (same_thread_group(p->real_parent, father))
return 0;
/* We don't want people slaying init. */
p->exit_signal = SIGCHLD;
/* If we'd notified the old parent about this child's death,
* also notify the new parent.
*/
dead = 0;
if (!p->ptrace &&
p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
do_notify_parent(p, p->exit_signal);
if (task_detached(p)) {
p->exit_state = EXIT_DEAD;
dead = 1;
}
}
kill_orphaned_pgrp(p, father);
return dead;
}
/*
* When we die, we re-parent all our children.
* Try to give them to another thread in our thread
@ -805,10 +765,46 @@ static struct task_struct *find_new_reaper(struct task_struct *father)
return pid_ns->child_reaper;
}
/*
* Any that need to be release_task'd are put on the @dead list.
*/
static void reparent_thread(struct task_struct *father, struct task_struct *p,
struct list_head *dead)
{
if (p->pdeath_signal)
group_send_sig_info(p->pdeath_signal, SEND_SIG_NOINFO, p);
list_move_tail(&p->sibling, &p->real_parent->children);
if (task_detached(p))
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))
return;
/* We don't want people slaying init. */
p->exit_signal = SIGCHLD;
/* If it has exited notify the new parent about this child's death. */
if (!p->ptrace &&
p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
do_notify_parent(p, p->exit_signal);
if (task_detached(p)) {
p->exit_state = EXIT_DEAD;
list_move_tail(&p->sibling, dead);
}
}
kill_orphaned_pgrp(p, father);
}
static void forget_original_parent(struct task_struct *father)
{
struct task_struct *p, *n, *reaper;
LIST_HEAD(ptrace_dead);
LIST_HEAD(dead_children);
exit_ptrace(father);
@ -821,15 +817,14 @@ static void forget_original_parent(struct task_struct *father)
BUG_ON(p->ptrace);
p->parent = p->real_parent;
}
if (reparent_thread(p, father))
list_add(&p->ptrace_entry, &ptrace_dead);;
reparent_thread(father, p, &dead_children);
}
write_unlock_irq(&tasklist_lock);
BUG_ON(!list_empty(&father->children));
list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {
list_del_init(&p->ptrace_entry);
list_for_each_entry_safe(p, n, &dead_children, sibling) {
list_del_init(&p->sibling);
release_task(p);
}
}