Commit 482a3767 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

exit: reparent: call forget_original_parent() under tasklist_lock 



Shift "release dead children" loop from forget_original_parent() to its
caller, exit_notify().  It is safe to reap them even if our parent reaps
us right after we drop tasklist_lock, those children no longer have any
connection to the exiting task.

And this allows us to avoid write_lock_irq(tasklist_lock) right after it
was released by forget_original_parent(), we can simply call it with
tasklist_lock held.

While at it, move the comment about forget_original_parent() up to
this function.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
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 ad9e206a

kernel/exit.c

+23 −24
Original line number Diff line number Diff line
@@ -560,19 +560,26 @@ static void reparent_leader(struct task_struct *father, struct task_struct *p, 
	kill_orphaned_pgrp(p, father);

}



static void forget_original_parent(struct task_struct *father)

/*

 * This does two things:

 *

 * A.  Make init inherit all the child processes

 * B.  Check to see if any process groups have become orphaned

 *	as a result of our exiting, and if they have any stopped

 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)

 */

static void forget_original_parent(struct task_struct *father,

					struct list_head *dead)

{

	struct task_struct *p, *t, *n, *reaper;

	LIST_HEAD(dead_children);

	struct task_struct *p, *t, *reaper;



	write_lock_irq(&tasklist_lock);

	if (unlikely(!list_empty(&father->ptraced)))

		exit_ptrace(father, &dead_children);

		exit_ptrace(father, dead);



	/* Can drop and reacquire tasklist_lock */

	reaper = find_child_reaper(father);

	if (list_empty(&father->children))

		goto unlock;

		return;



	reaper = find_new_reaper(father, reaper);

	list_for_each_entry(p, &father->children, sibling) {
@@ -590,16 +597,9 @@ static void forget_original_parent(struct task_struct *father) 
		 * notify anyone anything has happened.

		 */

		if (!same_thread_group(reaper, father))

			reparent_leader(father, p, &dead_children);

			reparent_leader(father, p, dead);

	}

	list_splice_tail_init(&father->children, &reaper->children);

 unlock:

	write_unlock_irq(&tasklist_lock);



	list_for_each_entry_safe(p, n, &dead_children, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

	}

}



/*
@@ -609,18 +609,12 @@ static void forget_original_parent(struct task_struct *father) 
static void exit_notify(struct task_struct *tsk, int group_dead)

{

	bool autoreap;



	/*

	 * This does two things:

	 *

	 * A.  Make init inherit all the child processes

	 * B.  Check to see if any process groups have become orphaned

	 *	as a result of our exiting, and if they have any stopped

	 *	jobs, send them a SIGHUP and then a SIGCONT.  (POSIX 3.2.2.2)

	 */

	forget_original_parent(tsk);

	struct task_struct *p, *n;

	LIST_HEAD(dead);



	write_lock_irq(&tasklist_lock);

	forget_original_parent(tsk, &dead);



	if (group_dead)

		kill_orphaned_pgrp(tsk->group_leader, NULL);
@@ -644,6 +638,11 @@ static void exit_notify(struct task_struct *tsk, int group_dead) 
		wake_up_process(tsk->signal->group_exit_task);

	write_unlock_irq(&tasklist_lock);



	list_for_each_entry_safe(p, n, &dead, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

	}



	/* If the process is dead, release it - nobody will wait for it */

	if (autoreap)

		release_task(tsk);

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