Commit 1109909c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

exit: reparent: introduce find_child_reaper() 



find_new_reaper() does 2 completely different things.  Not only it finds a
reaper, it also updates pid_ns->child_reaper or kills the whole namespace
if the caller is ->child_reaper.

Now that has_child_subreaper logic doesn't depend on child_reaper check we
can move that pid_ns code into a separate helper.  IMHO this makes the
code more clean, and this allows the next changes.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 175aed3f

kernel/exit.c

+35 −21
Original line number Diff line number Diff line
@@ -459,38 +459,50 @@ static void exit_mm(struct task_struct *tsk) 
	clear_thread_flag(TIF_MEMDIE);

}



/*

 * When we die, we re-parent all our children, and try to:

 * 1. give them to another thread in our thread group, if such a member exists

 * 2. give it to the first ancestor process which prctl'd itself as a

 *    child_subreaper for its children (like a service manager)

 * 3. give it to the init process (PID 1) in our pid namespace

 */

static struct task_struct *find_new_reaper(struct task_struct *father)

static struct task_struct *find_child_reaper(struct task_struct *father)

	__releases(&tasklist_lock)

	__acquires(&tasklist_lock)

{

	struct pid_namespace *pid_ns = task_active_pid_ns(father);

	struct task_struct *thread;

	struct task_struct *reaper = pid_ns->child_reaper;



	for_each_thread(father, thread) {

		if (thread->flags & PF_EXITING)

	if (likely(reaper != father))

		return reaper;



	for_each_thread(father, reaper) {

		if (reaper->flags & PF_EXITING)

			continue;

		if (unlikely(pid_ns->child_reaper == father))

			pid_ns->child_reaper = thread;

		return thread;

		pid_ns->child_reaper = reaper;

		return reaper;

	}



	if (unlikely(pid_ns->child_reaper == father)) {

	write_unlock_irq(&tasklist_lock);

	if (unlikely(pid_ns == &init_pid_ns)) {

		panic("Attempted to kill init! exitcode=0x%08x\n",

				father->signal->group_exit_code ?:

					father->exit_code);

			father->signal->group_exit_code ?: father->exit_code);

	}



	zap_pid_ns_processes(pid_ns);

	write_lock_irq(&tasklist_lock);



	return father;

}



/*

 * When we die, we re-parent all our children, and try to:

 * 1. give them to another thread in our thread group, if such a member exists

 * 2. give it to the first ancestor process which prctl'd itself as a

 *    child_subreaper for its children (like a service manager)

 * 3. give it to the init process (PID 1) in our pid namespace

 */

static struct task_struct *find_new_reaper(struct task_struct *father,

					   struct task_struct *child_reaper)

{

	struct task_struct *thread;



	for_each_thread(father, thread) {

		if (thread->flags & PF_EXITING)

			continue;

		return thread;

	}



	if (father->signal->has_child_subreaper) {
@@ -501,7 +513,7 @@ static struct task_struct *find_new_reaper(struct task_struct *father) 
		 * namespace, this is safe because all its threads are dead.

		 */

		for (reaper = father;

		     !same_thread_group(reaper, pid_ns->child_reaper);

		     !same_thread_group(reaper, child_reaper);

		     reaper = reaper->real_parent) {

			/* call_usermodehelper() descendants need this check */

			if (reaper == &init_task)
@@ -515,7 +527,7 @@ static struct task_struct *find_new_reaper(struct task_struct *father) 
		}

	}



	return pid_ns->child_reaper;

	return child_reaper;

}



/*
@@ -552,7 +564,9 @@ static void forget_original_parent(struct task_struct *father) 
		exit_ptrace(father, &dead_children);



	/* Can drop and reacquire tasklist_lock */

	reaper = find_new_reaper(father);

	reaper = find_child_reaper(father);



	reaper = find_new_reaper(father, reaper);

	list_for_each_entry(p, &father->children, sibling) {

		for_each_thread(p, t) {

			t->real_parent = reaper;