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Commit 5dfc80be authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

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: default avatarOleg 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 39c626ae

kernel/exit.c

+41 −46
Original line number Diff line number Diff line
@@ -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);

	}

}