Commit 05e83df6 authored Mar 02, 2008 by Oleg Nesterov Committed by Linus Torvalds Mar 03, 2008

will_become_orphaned_pgrp: partially fix insufficient ->exit_state check



p->exit_state != 0 doesn't mean this process is dead, it may have
sub-threads.  Change the code to use "p->exit_state && thread_group_empty(p)"
instead.

Without this patch, ^Z doesn't deliver SIGTSTP to the foreground process
if the main thread has exited.

However, the new check is not perfect either.  There is a window when
exit_notify() drops tasklist and before release_task().  Suppose that
the last (non-leader) thread exits.  This means that entire group exits,
but thread_group_empty() is not true yet.

As Eric pointed out, is_global_init() is wrong as well, but I did not
dare to do other changes.

Just for the record, has_stopped_jobs() is absolutely wrong too.  But we
can't fix it now, we should first fix SIGNAL_STOP_STOPPED issues.

Even with this patch ^Z doesn't play well with the dead main thread.
The task is stopped correctly but do_wait(WSTOPPED) won't see it.  This
is another unrelated issue, will be (hopefully) fixed separately.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f49ee505

kernel/exit.c

+8 −9

Original line number	Diff line number	Diff line
		@@ -214,20 +214,19 @@ struct pid session_of_pgrp(struct pid pgrp)
		static int will_become_orphaned_pgrp(struct pid pgrp, struct task_struct ignored_task)
		{
		struct task_struct *p;
		int ret = 1;

		do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
		if (p == ignored_task
		\|\| p->exit_state
		\|\| is_global_init(p->real_parent))
		if ((p == ignored_task) \|\|
		(p->exit_state && thread_group_empty(p)) \|\|
		is_global_init(p->real_parent))
		continue;

		if (task_pgrp(p->real_parent) != pgrp &&
		task_session(p->real_parent) == task_session(p)) {
		ret = 0;
		break;
		}
		task_session(p->real_parent) == task_session(p))
		return 0;
		} while_each_pid_task(pgrp, PIDTYPE_PGID, p);
		return ret; /* (sighing) "Often!" */

		return 1;
		}

		int is_current_pgrp_orphaned(void)